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Journal Cover Journal of Polymer Science Part A: Polymer Chemistry
  [SJR: 1.037]   [H-I: 123]   [133 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0360-6376 - ISSN (Online) 1099-0518
   Published by John Wiley and Sons Homepage  [1579 journals]
  • Cover Image, Volume 55, Issue 12
    • Abstract: On page 1971 (
      DOI : 10.1002/pola.28562), Wen-Hua Sun and colleagues describe nickel catalysts that can promote the polymerization of ethylene to give high molecular weight polyethylenes at temperatures up to 100°C. Significant branching (including methyl, ethyl and longer chain branches) is a feature of the polymers which is further evidenced by their low melting temperatures. These thermally robust a-diimine catalysts incorporating ortho-substituted difluorobenzhydryl groups impart unsymmetrical protection to the active species limiting decomposition pathways whilst maintaining high activity. The figure shows a segment of branched polyethylene above a roof-top image (from the Forbidden City) of a rooster leading out nine (infinite) animal figures before the immortal. (
      DOI : 10.1002/pola.28562)
      PubDate: 2017-05-03T02:32:27.714118-05:
       
  • Isosorbide telechelic bio-based oligomers
    • Authors: Jean-David Rodier; Vincenza D'Anna, Nicolas Ritter, Serge Dalicieux, Philippe Sautet, Jean-Pierre Pascault, Alain Rousseau, Etienne Fleury
      Abstract: This article deals with the preparation of novel co-oligoethers constituted with 1,3-propanediol (PDO) and isosorbide units and, prepared according to two different melt processes, without any solvent in the presence of acid catalyst: co-etherification of PDO and isosorbide (process A) and, trans-etherification between polytrimethylene ether glycol (PTEG) and isosorbide (process B). Complementary analytical methods: D and 2D 1H NMR and gas chromatography analysis, coupled with FID and MS-MALDI-TOF mass spectrometry, were performed to precisely define the microstructure of the final products. In particular, one can observe that two mechanisms involve during the reaction: etherification and trans-etherification where isosorbide reacts decreasing the molar mass of polymers chains. This led to oligomers having isosorbide units at each extremity and little inner isosorbide units. Computational calculations have been performed in parallel, and the data well duplicate the experimental results. Finally, it was shown that these new telechelic oligoethers have higher compatibility to water and higher Tg level and thermal stability than PTEG homopolymer. Therefore, such oligomers can be considered as new intermediates for designing new surfactants and/or new copolymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017Co-oligoethers were prepared according to two different processes. Process A is a co-etherification of 1,3-propanediol and isosorbide, and Process B is a transetherifcation of isosorbide and polytrimethylene ether glycol (PTEG). Both processes lead to telechelic structures having isosorbide units located at each chain extremity. These co-oligoethers have better thermal and solubility properties than PTEG and represent a novel and original bio-based macrodiols.
      PubDate: 2017-05-02T10:48:09.221239-05:
      DOI: 10.1002/pola.28603
       
  • An unusual photo-oxidation pathway for a poly(2,6-dimethyl-1,4-phenylene
           oxide) model compound
    • Authors: James E. Pickett
      Abstract: The long wavelength UV photochemistry was investigated of a model compound for poly(2,6-dimethyl-1,4-phenylene oxide). Irradiation of the phenyl-capped dimer of 2,6-dimethyl phenol at wavelengths >290 nm with UVA-340 fluorescent lamps in the absence of oxygen gave no detectable products after 27 days. Very low conversion to oxidation products was found in the presence of oxygen, but about 20% conversion to products in which solvent had added to the benzylic methyl groups occurred under aerobic conditions when the solvents had readily abstractable hydrogen atoms. A mechanism is proposed involving the facile, reversible abstraction of a benzylic hydrogen by oxygen as a first step in the oxidation. The hydroperoxyl radical that is formed can abstract hydrogen atoms from 2° and 3° carbons of the solvent, and these radicals can combine with the benzylic radicals to give the solvent adducts. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017A model compound for poly(2,6-dimethyl-1,4-phenylene oxide) did not exhibit ether bond photolysis when irradiated with UV >290 nm. Rather, it gave products of solvent addition to the methyl groups. This unexpected reaction may proceed from hydrogen abstraction by oxygen from the excited triplet state or from a charge transfer complex.
      PubDate: 2017-05-02T10:47:53.365474-05:
      DOI: 10.1002/pola.28608
       
  • Influence of hydrophobic monomers on secondary nucleation of
           hydroxyl-functionalized latexes
    • Authors: Martin Ocepek; Weijie Zhong, Lei Meng, Mark D. Soucek
      Abstract: The influence of butyl acrylate (BA) and methyl methacrylate (MMA) on hydroxyl functionalized latexes was investigated. The hydrophobicity of the monomer feed was varied via the BA/MMA ratio. In addition to monitoring the effect of hydrophobic monomer feed on secondary nucleation, the polymerization kinetics and final latex properties were also obtained for comparison. Five different BA to MMA molar ratios were combined with five 2-hydroxyethyl methacrylate (HEMA) concentrations (0, 10, 20, 30 and 40 mol% in monomer composition). All latexes were synthesized through seeded semibatch emulsion polymerization process. Particle size distributions and average particle sizes of the latexes were determined by dynamic light scattering (DLS) and qualitatively compared with transmission electron microscope (TEM) images. The BA to MMA ratio significantly influences the boundary HEMA concentration at which homogeneous secondary nucleation occurs. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017Poly(BA-co-MMA-co-HEMA) based latexes were investigated by dynamic light scattering (DLS) and transmission electron microscope (TEM). Focus was put on the effect of the BA to MMA ratio on secondary nucleation at increasing HEMA content. All the latexes were prepared via seeded semibatch emulsion polymerization process. The authors found that the BA to MMA ratio significantly influences the boundary HEMA concentration at which homogeneous secondary nucleation occurs.
      PubDate: 2017-05-02T10:00:34.092021-05:
      DOI: 10.1002/pola.28604
       
  • Iodinated polyesters as a versatile platform for radiopaque biomaterials
    • Authors: Katelyn R. Houston; Sarah M. Brosnan, Laurel M. Burk, Yueh Z. Lee, J. Christopher Luft, Valerie Sheares Ashby
      Abstract: The design of polymeric biomaterials with long-lasting X-ray contrast could advance safe and effective implants and contrast agents. Herein, a new set of wholly aliphatic, iodinated polyesters are synthesized and evaluated as high-contrast biomaterials and nanoparticle contrast agents for general computed tomography imaging. A single iodinated monomer is used to synthesize a variety of aliphatic polyesters with tunable thermal and mechanical properties. These iodinated polyesters are end-functionalized with a photocurable methacrylate group, which allows easy processability. The resulting materials exhibit no cytotoxicity and are radiopaque, containing over 40% iodine by weight after processing. The polymers can be formulated into lipid–polymer hybrid nanoparticles using a modified nanoprecipitation method. Initial studies indicate that these nanoparticles show good continual contrast over 60 minutes with no uptake into the kidneys. The work presented here illustrates a novel platform for iodinated polyesters that exhibit high radiopacity and processability, low cost, and no cytotoxicity. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017A variety of aliphatic, radiopaque polyesters are synthesized and evaluated using a unique, iodinated monomer. These polymers exhibit high radiocontrast, tunable thermal and mechanical properties, and low cytotoxicity. They can be easily processed into both nanoparticles and thermosets. These nanoparticles show good continual contrast with no uptake into the kidneys. This new platform of radiopaque biomaterials could contribute toward the development of safer, more effective implants and contrast agents.
      PubDate: 2017-05-02T10:00:30.342871-05:
      DOI: 10.1002/pola.28596
       
  • Deep-blue light-emitting polyfluorenes containing
           spiro[fluorene-9,9′-thioxanthene-S,S-dioxide] isomers
    • Authors: Feng Peng; Jin Xu, Yuhao Zhang, Ruifeng He, Wei Yang, Yong Cao
      Abstract: Blue light-emitting polyfluorenes, PPF-FSOs and PPF-SOFs were synthesized via introducing spiro[fluorene-9,9′-thioxanthene-S,S-dioxide] isomers (2,7-diyl and 2′,7′-diyl) (FSO/SOF) into the poly[9,9-bis(4-(2-ethylhexyloxy) phenyl)fluorene-2,7-diyl] (PPF) backbone, respectively. With the increasing contents of FSO and SOF moieties, the absorption and PL spectra of PPF-FSOs show slight red shift, while that of PPF-SOFs exhibit blue shift, respectively. The HOMO and LUMO levels reduce gradually with increasing SOF unit in PPF-SOFs. The polymers emit blue light peaked around 430–445 nm and show an excellent spectral stability with the variation in current densities. The distinctly narrowing EL spectra were observed with the incorporation of isomers in the polymers. The full width at half maximum reduced by 15 nm for PPF-SOFs, resulting in a blue shift with the CIE coordinates from (0.16, 0.11) to (0.16, 0.08). With a device configuration of ITO/PEDOT:PSS/EML/CsF/Al, a maximum luminance efficiency (LEmax) of 2.00 cd A−1, a maximum external quantum efficiency (EQEmax) of 3.76% with the CIE coordinates of (0.16, 0.08) for PPF-SOF15 and a LEmax of 1.68 cd A−1, a EQEmax of 2.38% with CIE (0.16, 0.12) for PPF-FSO10 were obtained, respectively. The result reveals that spiro[fluorene-9,9′-thioxanthene-S,S-dioxide] isomers are promising blocks for deep-blue light-emitting polymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017PPF-FSOs and PPF-SOFs containing spiro[fluorene-9,9′-thioxanthene-S,S-dioxide] isomers (2,7-diyl and 2′,7′-diyl) (FSO/SOF) emit blue light peaked around 430–445 nm with an excellent spectral stability. The distinctly narrowing emission was observed with the increasing content of isomers in the polymers. The nonconjugated SOF moiety in the polyfluorene backbone effectively disturbed the conjugation, restrained intramolecular charge transfer effect and kept a deep blue emission with Commission International de l Eclairge coordinate around (0.16, 0.08). A EQEmax of 3.76% was obtained from the single-layer device based on PPF-SOF15, which denoted a threefold enhancement compared with poly[9,9-bis(4-(2-ethylhexyloxy) phenyl)fluorene-2,7-diyl]-based device.
      PubDate: 2017-04-29T00:21:47.733248-05:
      DOI: 10.1002/pola.28618
       
  • Graft polymer synthesis by RAFT transfer-to
    • Authors: Jeffrey C. Foster; Scott C. Radzinski, John B. Matson
      Abstract: The synthesis of graft polymers via controlled polymerization techniques has enabled the facile modification of the surface properties of a variety of substrates. Three grafting methods are typically highlighted in the literature: grafting-to, grafting-from, and grafting-through. However, a fourth method exists when grafting is conducted using reversible addition-fragmentation chain transfer (RAFT) polymerization, which we refer to as transfer-to. Transfer-to differs from the other grafting strategies in the types of structural defects and impurities that arise during polymerization. This review addresses important considerations when conducting RAFT transfer-to, including RAFT chain transfer agent selection, monomer structure, and reaction conditions. In addition, we highlight key mechanistic differences between grafting-from and transfer-to and their effects on the structure and sample composition of the resulting graft polymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017Three grafting methods are typically utilized: grafting-to, grafting-from, and grafting-through. A fourth method exists when conducting RAFT polymerization: transfer-to. Transfer-to differs from the other grafting strategies in the types of structural defects and impurities that arise during polymerization. This review addresses important considerations when conducting RAFT transfer-to graft polymerization. In addition, we highlight key mechanistic differences between grafting-from and transfer-to and their effects on the structure and sample composition of the resulting graft polymers.
      PubDate: 2017-04-29T00:21:45.086978-05:
      DOI: 10.1002/pola.28621
       
  • Formation of homogeneous nanocomposite films at ambient temperature via
           miniemulsion polymerization using graphene oxide as surfactant
    • Authors: Yasemin Fadil; S. H. Che Man, Florent Jasinski, Hideto Minami, Stuart C. Thickett, Per B. Zetterlund
      Abstract: A convenient and industrially scalable method for synthesis of homogeneous nanocomposite films comprising poly(styrene-stat-butyl acrylate) and nanodimensional graphene oxide (GO) or reduced GO (rGO) is presented. Importantly, the nanocomposite latex undergoes film formation at ambient temperature, thus alleviating any need for high temperature or high pressure methods such as compression molding. The method entails synthesis of an aqueous nanocomposite latex via miniemulsion copolymerization relying on nanodimensional GO sheets as sole surfactant, followed by ambient temperature film formation resulting in homogeneous film. For comparison, a similar latex obtained by physical mixing of a polymer latex with an aqueous GO dispersion results in severe phase separation, illustrating that the miniemulsion approach using GO as surfactant is key to obtaining homogeneous nanocomposite films. Finally, it is demonstrated that the GO sheets can be readily reduced to rGO in situ by heat treatment of the film. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017This research presents a synthetic route to homogeneous nanocomposite polymer/reduced graphene oxide ambient temperature film forming materials. The method involves aqueous miniemulsion copolymerization of styrene and butyl acrylate using nanodimensional graphene oxide sheets as the sole surfactant in the absence of added conventional surfactants.
      PubDate: 2017-04-29T00:21:42.240759-05:
      DOI: 10.1002/pola.28613
       
  • A Free-standing electrochromic material of
           poly(5,7-bis(2-(3,4-ethylenedioxy)thienyl)-indole) and its application in
           electrochromic device
    • Authors: Xiaoyan Yang; Changlong Liu, Jiabao Guo, Ling Wang, Guangming Nie
      Abstract: Free-standing poly(5,7-bis(2-(3,4-ethylenedioxy)thienyl)-indole) (PETI) was electrochemically obtained from 5,7-bis(2-(3,4-ethylenedioxy)thienyl)-indole (ETI) prepared by Stille coupling reaction of 5,7-dibromoindole and 3,4-ethylenedioxythiophene. For comparison, poly(5,7-bis(2-thiophene)-indole) was also electrosynthesized from 5,7-bis(2-thiophene)-indole (BTI) which was prepared from the 5,7-dibromoindole and thiophene. Characterizations of ETI and BTI were performed by cyclic voltammetry, scanning electron microscopy, 1H NMR, and 13C NMR spectroscopy. Spectroelectrochemical studies showed PETI had better electrochromic properties and showed two different colors (brown and blue-violet) under various potentials with better maximum contrast (ΔT%) and coloration efficiency (CE). An electrochromic device (ECD) based on PETI and poly(3,4-ethylenedioxythiophene) (PEDOT) was also constructed and characterized. This ECD had fast response time, high CE, better optical memory, and long-term stability. These results indicated that PETI had potential applications for ECD. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017Free-standing poly(5,7-bis(2-(3,4-ethylenedioxy)thienyl)-indole) (PETI) was synthesized electrochemically in an acetonitrile solution. The polymer film shows reversible electrochemical processes and stable color change. Spectroelectrochemistry indicates that PETI has good electrochromic properties. The electrochromic device based on PETI and poly(3,4-ethylenedioxythiophene) is also fabricated and shows good electrochromic performance.
      PubDate: 2017-04-29T00:21:37.983258-05:
      DOI: 10.1002/pola.28624
       
  • Hydroxide-ion transport and stability of diblock copolymers with a
           polydiallyldimethyl ammonium hydroxide block
    • Authors: Pepa Cotanda; Nikos Petzetakis, Xi Jiang, Greg Stone, Nitash P. Balsara
      Abstract: Base-stable amphiphilic diblock copolymers with a polydiallyl dimethyl ammonium hydroxide block were synthesized and characterized to quantify hydroxide-ion transport in the hydrated state; polystyrene was the hydrophobic block. The challenge of synthesizing a copolymer comprising blocks with very different solubility behaviors was addressed by a combination of reversible addition fragmentation chain transfer polymerization and ion metathesis. Both monomers used in the polymerization are commercially available on industrial scales. Hydroxide-ion conductivities of 0.8 mS/cm were achieved in hot-pressed membranes immersed in water at room temperature despite relatively low water uptake (4.2 water molecules per hydroxide ion). The stability of the polydimethyl ammonium hydroxide chains was investigated in 2 M NaOD at 60 °C. 1H NMR spectroscopy studies showed no detectable degradation after 2000 hours. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017Base-stable amphiphilic diblock copolymers with a polydiallyl dimethyl ammonium hydroxide block were synthesized and characterized to quantify hydroxide-ion transport in the hydrated state; polystyrene was the hydrophobic block. A copolymer comprising blocks with very different solubility behaviors was synthesized by a combination of reversible addition fragmentation chain transfer polymerization and ion metathesis. Hydroxide-ion conductivities of 0.8 mS/cm were achieved. Both monomers are commercially available on industrial scales. 1H NMR spectroscopy studies showed no detectable degradation after 2000 hours.
      PubDate: 2017-04-29T00:20:43.062432-05:
      DOI: 10.1002/pola.28611
       
  • Symmetrical polymer systems prepared using a degradable bifunctional atom
           transfer radical polymerization initiator: Synthesis, characterization,
           and cleavage
    • Authors: Marios Elladiou; Andreas S. Kalogirou, Costas S. Patrickios
      Abstract: Linear (co)polymers and dimethacrylate-end-linked polymer networks of methyl methacrylate with 2-(dimethylamino)ethyl methacrylate, cleavable in the middle of the polymer chain, either under thermolysis or alkaline hydrolysis conditions, were prepared via atom transfer radical polymerization (ATRP) using a specially designed bifunctional degradable initiator. This initiator was 2,6-pyridinediethanol di(2-bromo-2-methyl propanoate) (PyDEDBrMeP), bearing two 2-(pyridin-2-yl)ethyl ester moieties, known for their thermal and hydrolytic (alkaline conditions) lability. As a control, a more stable bifunctional ATRP initiator, 2,6-pyridinedimethanol di(2-bromo-2-methyl propanoate) (PyDMDBrMeP), was also synthesized together with the corresponding linear polymers and polymer networks prepared from it. Thermal or hydrolytic treatment of the polymers prepared using PyDEDBrMeP led to a reduction in the molecular weights of the linear polymers by a factor of two, and to the conversion of the polymer networks to soluble branched (star) structures, consistent with the expected cleavage of the initiator residue located in the middle of the polymer chain. Thermal treatment of the polymers prepared using PyDMDBrMeP did not affect their molecular weight due to the thermal stability of the (pyridin-2-yl)methyl ester group, while treatment under alkaline hydrolysis conditions resulted in complete cleavage, similar to the PyDEDBrMeP-prepared polymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017A degradable bifunctional atom transfer radical polymerization initiator based on 2,6-pyridinediethanol was developed and used to prepare linear homo- and copolymers, as well as hyperbranched polymer (sketched in the graphic) and polymer networks. These could be cleaved by thermolysis or mild alkaline hydrolysis conditions at the site of the labile initiator residue, in the middle of the polymer chain.
      PubDate: 2017-04-26T04:20:38.401789-05:
      DOI: 10.1002/pola.28620
       
  • Morphology control and inducing a curvature on the domain interface by
           increasing the steric bulk of polymethacrylate in POSS-containing diblock
           copolymers
    • Authors: Fuminobu Kato; Shin Sugimoto, Alvin Chandra, Teruaki Hayakawa
      Abstract: Herein, a novel rod-coil type polyhedral oligomeric silsesquioxane (POSS)-containing diblock copolymer was designed to enable the self-assembly of hexagonally packed cylinders of the POSS-containing domain in a poly(n-butyl methacrylate) (PnBMA) matrix. When POSS-containing diblock copolymers were synthesized with polyisoprene or poly(methyl methacrylate), cylindrical structures could not be obtained as POSS-containing polymers form stretched rigid rods. This makes the formation of cylindrical structures with the POSS-containing domain entropically unfavorable. Therefore, to obtain the cylindrical structures, we constructed a novel diblock copolymer using PnBMA to increase the steric bulk and segment volume of the flexible coil. Steric crowding of the butyl groups reduces the entropic free stretching energy of the PnBMA chains, which in turn encourages the formation of a POSS-containing hexagonally packed cylindrical structure within the PnBMA matrix as the system minimizes the total free energy of the thermodynamically stable nanostructure. Small angle X-ray scattering and transmission electron microscopy analyses indicated that cylinders of the POSS domain had formed. Oxygen plasma etching was then used on the thin film to selectively remove the PnBMA domain to yield line and space structures with a high degree of long-range order and a 14 nm feature size. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017This research develops an original synthetic technique for obtaining additional self-assembled morphologies in diblock copolymers unable to form cylindrical nanostructures of PMAPOSS. The use of a flexible coil block with a significantly increased steric bulk [i.e., poly(n-butyl methacrylate)] allowed for the formation of cylindrical structures containing the rigid POSS domain.
      PubDate: 2017-04-25T21:35:45.112123-05:
      DOI: 10.1002/pola.28610
       
  • Hydrogenation of polystyrene-b-polybutadiene-b-polystyrene mediated by
           group (IV) metal metallocene complexes
    • Authors: Cheng-Hung Chiang; Jing-Cherng Tsai
      Abstract: Various group (IV) metal complexes, namely bis(cyclopentadienyl) titanium dichloride, bis(pentamethylcyclopentadienyl) titanium dichloride, cyclopentadienyl titanium trichloride, pentamethylcyclopentadienyl titanium trichloride, bis(cyclopentadienyl) zirconium dichloride, and bis(cyclopentadienyl) hafnium dichloride, were used as the catalysts for mediating styrene–butadiene–styrene hydrogenation. The catalytic efficiency of these catalysts was examined. The results show that catalyst activity strongly depends on the chemical structure of the metallocene complex. We also found that trialkylaluminum has a significant influence on the hydrogenation activity and thermal stability of metallocene catalysts. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017Hydrogenation of styrene-butadiene-styrene triblock copolymer using Cp2TiCl2/n-BuLi as catalyst shows distinctive activity differences with or without adding trialkylaluminum. The addition of trialkylaluminum leads to the generation of a trivalent Ti(III) complex, which prefers a higher reaction temperature. By contrast, in the absence of trialkylaluminum, the Ti(IV) metallocene catalyst displays a lower reaction temperature preference. Both catalyst systems display excellent hydrogenation activity under a proper selection of reaction temperature.
      PubDate: 2017-04-25T21:35:42.589042-05:
      DOI: 10.1002/pola.28589
       
  • Efficient synthesis and RAFT polymerization of the previously elusive
           N-[(cycloalkylamino)methyl]acrylamide monomer class
    • Authors: Benjamin A. Chalmers; Abdullah Alzahrani, Gerard Hawkins, Fawaz Aldabbagh
      Abstract: Schiff base salts allowed the multigram preparation of methylene amino substituted acrylamide monomers. These, as well as the hydrochloride salt intermediates, were subjected to controlled/living polymerizations for the first time. One-pot sequential reversible addition-fragmentation chain transfer (RAFT) polymerizations resulted in well-defined di- and triblock copolymers.
      PubDate: 2017-04-25T21:35:37.697562-05:
      DOI: 10.1002/pola.28607
       
  • Multinuclear cobalt–salen complexes with phenylene linker for
           epoxide polymerizations
    • Authors: Yo Hiranoi; Miho Hatanaka, Koji Nakano
      Abstract: Di- and trinuclear cobalt (Co)–salen complexes with a benzene ring as a rigid linker were explored for epoxide polymerizations. The dinuclear Co–salen complex with a 1,2-phenylene linker showed higher catalytic activity than the dinuclear Co–salen complex with a 1,3-phenylene linker and the trinuclear Co–salen complex with a 1,3,5-benzenetriyl linker for the copolymerization of propylene oxide (PO) with carbon dioxide. A combination of the absolute configuration of the two Co–salen moieties was found to affect its catalytic activity. The optimized dinuclear Co–salen complex with a heterochiral combination demonstrated highest activity and maintained its catalytic activity under a low catalyst concentration. The heterochiral dinuclear Co–salen complex also showed high activity for the copolymerization of PO with cyclic anhydride. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017The dinuclear Co–salen complex with a 1,2-phenylene linker exhibited higher catalytic activities for the epoxide/carbon dioxide copolymerization and the epoxide/cyclic anhydride copolymerization than the mononuclear Co–salen complexes.
      PubDate: 2017-04-25T21:35:34.450447-05:
      DOI: 10.1002/pola.28590
       
  • Effect of the structure of titanium–magnesium catalysts on the
           morphology of polyethylene produced
    • Authors: Tatiana B. Mikenas; Evgeny I. Koshevoy, Vladimir A. Zakharov
      Abstract: The structure and formation of polyethylene (PE) particles on supported titanium–magnesium catalysts having different structural characteristics (sizes of microcrystallites, mesopores, and subparticles) were studied for the first time. Scanning electron microscopy was used to identify structural elements of the polymer particles formed over such catalysts and to reveal morphological changes in the growing polymer particles when the yield was increased from approximately 0.2 g PE/g catalyst to approximately 13 kg PE/g catalyst. A relationship was found between structural characteristics of the porous catalyst particles, morphology of the nascent polymer particles, and bulk density of the polymer powder. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017This research finds a relationship between structural characteristics of porous catalyst particles, morphology of nascent polymer particles, and bulk density of polymer powder. Catalyst particles consisting of globular subparticles with high packing density—comprising close-packed globular microparticles with small mesopores and crystallites—produce PE with high bulk density.
      PubDate: 2017-04-21T06:10:52.743865-05:
      DOI: 10.1002/pola.28614
       
  • Photo-oxidation of poly(2,6-dimethyl-1,4-phenylene oxide): A
           reinvestigation
    • Authors: James E. Pickett
      Abstract: Reinvestigation of poly(2,6-dimethyl-1,4-phenylene oxide) photodegradation at wavelengths > 290 nm shows that both methyl groups and aromatic rings are sites of oxidation with their relative rates dependent on exposure conditions, based on infrared spectroscopy. The methyl group loss is linear with exposure and apparently proceeds by direct abstraction of a benzylic hydrogen by oxygen. The aromatic ring loss and carbonyl growth in the IR spectra appear to be auto-accelerating and seem to proceed by electron transfer to oxygen, either sensitized or through a direct reaction with oxygen, and recombination of the polymer radical cation and superoxide to result in oxygen addition to the ring. Molecular weight loss in solution occurs to a significant degree only in the presence of oxygen, even in the presence of a hydrogen-donating solvent, indicating that aryl ether photolysis is not a major pathway. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017Poly(phenylene oxide) undergoes photo-oxidation resulting in chain cleavage and yellowing. Purified, capped polymer degrades only slightly more slowly than as-made, extruded polymer. At least two independent processes are at work: fast ring oxidation that appears to be sensitized by photodegradation products and slow methyl group oxidation that proceeds at a constant rate. Direct ether photolysis is at most a minor pathway.
      PubDate: 2017-04-20T04:03:22.167928-05:
      DOI: 10.1002/pola.28616
       
  • Further insight into the mechanism of poly(styrene-co-methyl methacrylate)
           microsphere formation
    • Authors: Samantha I. Applin; Russell C. Schmitz, Pacita I. Tiemsin, Jan Genzer, John W. Connell, Christopher J. Wohl
      Abstract: Polymeric microspheres have been used in a broad range of applications from chromatographic separation techniques to analysis of air flow over aerodynamic surfaces. The preparation of microspheres from many polymer families has consequently been extensively studied using a variety of synthetic approaches. Although there are a myriad of polymeric microsphere synthesis methods, free-radical initiated emulsion polymerization is one of the most common techniques. In this work, poly(styrene-co-methyl methacrylate) microspheres were synthesized via surfactant-free emulsion polymerization. The effects of co-monomer composition and addition time on particle size distribution, particle formation, and particle morphology were investigated. Particles were characterized using dynamic light scattering and scanning electron microscopy to gain further insight into particle size and size distributions. Reaction kinetics were analyzed through consideration of characterization results. A particle formation mechanism for poly(styrene-co-methyl methacrylate) microspheres was proposed based on characterization results and known reaction kinetics. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017Poly(styrene-co-methyl methacrylate) microspheres were synthesized via surfactant-free emulsion polymerization. The effects of co-monomer composition and the addition time on particle size distribution, particle formation, and particle morphology were investigated using dynamic light scattering and scanning electron microscopy. Reaction kinetics was analyzed alongside characterization, and a particle formation mechanism was proposed.
      PubDate: 2017-04-20T04:02:42.865347-05:
      DOI: 10.1002/pola.28612
       
  • Nanofibers prepared by electrospinning from solutions of biobased
           polyamide 4
    • Authors: Lenka Blažková; Lenka Malinová, Václava Benešová, Jan Roda, Jiří Brožek
      Abstract: A successful preparation of polyamide 4 nanofibers via electrostatic spinning with diameters close to 100 nm is described. Polyamide 4 was prepared by the anionic ring-opening polymerization of 2-pyrrolidone and characterized. The effect of the system parameters (i.e., molar mass of the polymer, the solvent system) and the process parameters (i.e., the electrode-to-collector distance) during the electrostatic spinning have been studied. The morphology of the polyamide 4 fiber layers is given except molar mass of the polymer and the concentration of its solution primarily by the conformation of polyamide chains due to polyelectrolyte effect which was confirmed by viscosity measurements. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017The electrospinning from solutions represents an elegant method for processing thermally unstable polyamide 4. The morphology of the fiber layers being formed during the electrospinning depends on the molar mass of polymer, the solvent system used, the concentration of the solution and the presence of salt. Fibers with diameters close to 100 nm were obtained.
      PubDate: 2017-04-16T10:15:31.017733-05:
      DOI: 10.1002/pola.28605
       
  • Synthesis of ethylene/vinyl ester copolymers with pendent linear branches
           via ring-opening metathesis polymerization of fatty acid-derived
           cyclooctenes
    • Authors: Yuchen Feng; Suyun Jie, Bo-Geng Li
      Abstract: Fatty acid-derived cyclooctenes, including n-hexanoic acid (M1), n-octanoic acid (M2), lauric acid (M3), and palmitic acid (M4), were prepared as monomers and polymerized by ring-opening metathesis polymerization (ROMP) using Grubbs second-generation catalyst (G2). In all the cases, the regio-irregular unsaturated polymers with pendent linear branches were obtained, which could be saturated by chemical hydrogenation with TSH/TPA in high conversion, yielding ethylene/vinyl ester copolymers with pendent linear branches on precisely every eighth backbone carbon. Both unsaturated and saturated polymers were amorphous, and their structures were characterized by FTIR, 1H and 13C NMR spectra, and elemental analysis. Differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA) were used to study their thermal properties. The chain length of branches greatly affected the thermal properties of polymers. After hydrogenation, the thermal degradation stability of polymers was relatively improved. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017The ethylene/vinyl ester copolymers with pendent linear branches have been synthesized via ROMP of fatty acid-derived cyclooctenes, followed by chemical hydrogenation. The unsaturated polymers are regio-irregular and the hydrogenated polymers could be regarded as ethylene/vinyl ester copolymers with precisely long linear branches on every eighth backbone carbon. The chain length of branches greatly affected the thermal properties of polymers.
      PubDate: 2017-04-16T10:15:29.103631-05:
      DOI: 10.1002/pola.28606
       
  • Convenient synthetic route to tetraarylphosphonium polyelectrolytes via
           palladium-catalyzed P–C coupling of aryl triflates and diphenylphosphine
           
    • Authors: Wang Wan; Xiaoyan Yang, Rhett C. Smith
      Abstract: A series of eight tetraarylphosphonium polyelectrolytes (TPELs) has been successfully synthesized by polymerization of diphenylphosphine and bis(aryl triflate)s. The bis(aryl triflate)s are readily prepared from bisphenols, some of which are commodity feedstocks such as bisphenol A. The polymerization via palladium catalyzed P–C bond formation produces degrees of polymerization up to 65. All polymeric triflates have reasonable thermal stability in the range of 350–450 °C. The stability of the TPELs to alkaline solution is strongly depending on the spacer between adjacent phosphonium sites. Polymers with electron-releasing and bulky substituent para- to the phosphonium site have improved stability while those with electron-withdrawing substituent para- to phosphonium site have decreased alkaline stability due to decomposition via a nucleophilic aromatic substitution pathway. These findings have important ramifications for the design of ionomers for alkaline exchange membrane fuel cells and related electrochemical energy conversion devices. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017A P–C bond-forming reaction has been applied to the convenient preparation of tetraarylphosphonium polyelectrolytes (TPELs) from aryl triflates and diphenylphosphine. The thermal and alkaline stability of the materials is assessed.
      PubDate: 2017-04-14T20:15:36.814133-05:
      DOI: 10.1002/pola.28564
       
  • Grubbs-inspired metathesis in the Moore group
    • Authors: Timothy P. Moneypenny; Huiying Liu, Anna Yang, Ian D. Robertson, Jeffrey S. Moore
      Abstract: Alkene metathesis has proven to be a powerful method for carboncarbon bond formation, particularly in the field of polymer and materials science. The availability of various tailor-made catalysts not only enables the synthesis of well-defined polymers but facilitates the development of functional, stimuli–responsive materials. This highlight, dedicated to Professor Robert Grubbs on his 75th birthday, focuses on the various research efforts in our group utilizing both alkene and alkyne metatheses and the interesting materials derived from them. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017Polymer and materials science has significantly benefited from fundamental advances in olefin metathesis. The commercially available assortment of well-defined, highly active ruthenium metathesis catalysts enables the synthesis of functional macromolecules with controlled architectures and narrow molecular weight distributions. In this highlight article, dedicated to Professor Robert Grubbs' 75th birthday, we discuss our research efforts involving both olefin and alkyne metatheses with particular emphasis on inspiration garnered from Prof. Grubbs' ideology.
      PubDate: 2017-04-13T09:19:35.973364-05:
      DOI: 10.1002/pola.28592
       
  • Stimuli-responsive 4-acryloylmorpholine/4-acryloylpiperidine copolymers
           via nitroxide mediated polymerization
    • Authors: Xeniya Savelyeva; Adrien Métafiot, Lucia Li, Ian Bennett, Milan Marić
      Abstract: 4-acryloylmorpholine/4-acryloylpiperidine statistical copolymers were synthesized by nitroxide mediated polymerization (NMP) with BlocBuilder unimolecular initiator in dimethylformamide solution at 120 °C. The copolymers had narrow molecular weight distributions (dispersity Đ = 1.25–1.35, number average molecular weights Mn = 8.5–13.7 kg mol−1). The copolymer microstructure was essentially statistical (reactivity ratios r4AP = 0.81 ± 0.73, r4AM = 0.73 ± 0.68 based on non-linear fitting of the Mayo-Lewis equation). Cloud point temperatures (CPT) in aqueous media were tuned from 11 °C to 92 °C, merely by adjusting the initial monomer composition. Using NMP permitted sharper control of the CPT transitions, compared to the similar copolymer made using conventional radical polymerization. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017.Copolymerization of two structurally similar monomers, 4-acryloylmorpholine and 4-acryloylpiperidine, via nitroxide mediated polymerization afforded copolymers with tunable cloud point temperatures (CPTs) and sharp transitions with narrow molecular weight distributions (1.25–1.35). These copolymers span a wider range of CPTs, starting from as low as 4 °C, broadening the scope for potential applications.
      PubDate: 2017-04-13T09:18:37.745816-05:
      DOI: 10.1002/pola.28591
       
  • Coil-helix and sheet-helix block copolymers via macroinitiation from
           telechelic ROMP polymers
    • Authors: Elizabeth Elacqua; Anna Croom, Diane S. Lye, Marcus Weck
      Abstract: Coil-helix and sheet-helix block copolymers are synthesized by combining the ring-opening metathesis polymerization (ROMP) of norbornene or paracyclophanediene with the anionic polymerization of phenyl isocyanide. Key to the design is the use of an μ-ethynyl palladium (II) functionalized chain-transfer agent (CTA) that can be exploited in a stepwise manner for the termination of ROMP and the initiation of the anionic polymerization. Both the coil- and sheet-macroinitiators, and the ensuing covalent block copolymers, are analyzed using 1H NMR spectroscopy and gel-permeation chromatography. In all cases, the Pd-end group is maintained and all polymers demonstrate a monomodal distribution with dispersities (Đ) of 1.1–1.4. The resulting helix-coil and helix-sheet block copolymers formed by the macroinitiation route still demonstrate their intrinsic properties (fluorescence, preferential helix-sense). © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017.ROMP of norbornene and paracyclophanediene monomers, combined with the anionic polymerization of a phenyl isocyanide leads to the formation of coil-helix and sheet-helix block copolymers in a stepwise fashion. The coil and sheet ROMP polymers are ω-functionalized with an ethynyl-Pd complex that initiates the polymerization of the helical block. The resulting copolymers display the same intrinsic properties (e.g., helicity, fluorescence) as their parent polymers.
      PubDate: 2017-04-13T09:18:34.220666-05:
      DOI: 10.1002/pola.28542
       
  • Synthesis of hyperbranched polymers from vegetable oil based monomers via
           ozonolysis pathway
    • Authors: Jingjiang Sun; Kamal I. Aly, Dirk Kuckling
      Abstract: In this work, a variety of hyperbranched polymers (HBPs), such as hyperbranched polycarbonates, polyesters, polyurethanes and polyacetals, was successfully synthesized from castor oil and soybean oil based monomers via a A2 + B3 polycondensation. First, B3 monomer triols (TriOL), trialdehydes (TriAD), and tricarboxylic acids (TriAC) were obtained by ozonolysis of castor oil and soybean oil with following reductive or oxidative treatment. Their structures were characterized by 1H NMR and ATR-FTIR spectroscopy as well as electrospray ionization-Time of Flight-mass spectrometry. These trifunctional B3 monomers were applied in the preparation of HBPs. The resulting HBPs had number averaged molar mass (Mn) up to 9400 g/mol and weight averaged molar mass (Mw) up to 40,000 g/mol. Through adjusting the initial molar ratio of A2 to B3 monomers, hydroxyl terminated (from TriOL monomers) or carboxylic acid (from TriAC monomers) terminated HBPs could be obtained. All the HBPs were characterized by 1H NMR, size exclusion chromatography, and DSC. These HBPs are potential candidates for the synthesis of cross-linked polymeric materials or in biomedical applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017The utilization of vegetable oils as renewable resources in polymeric material application has attracted significant attention due to their renewability, low cost, low toxicity, inherent biodegradability, and versatile functionality. In this work, trialcohol, trialdehyde, and tricarboxylic acid were synthesized by using ozonolysis of castor oil and soybean oil. Using these B3 monomers, a variety of hyperbranched polymers, such as hyperbranched polyester, polycarbonate, polyacetal and polyurethane, were successfully prepared by A2 + B3 polycondensation.
      PubDate: 2017-04-13T09:18:17.578717-05:
      DOI: 10.1002/pola.28600
       
  • Biomimetic pH/redox dual stimuli-responsive zwitterionic polymer block
           poly(L-histidine) micelles for intracellular delivery of doxorubicin into
           tumor cells
    • Authors: Johnson V. John; Saji Uthaman, Rimesh Augustine, Kamali Manickavasagam Lekshmi, In-Kyu Park, Il Kim
      Abstract: A series of pH/redox dual stimuli-responsive poly(2-methacryloyloxyethyl phosphorylcholine)25-block-poly(l-histidine)n (p[MPC])25-b-p[His]n, n = 20, 35, 50, and 75) copolymers consisting of a pH-responsive p(His)n block and a biocompatible phospholipid analog p(MPC) block connected by a redox-responsive disulfide linker have been synthesized. The block copolymers are self-assembled into uniform micelles (∼100 nm) in which doxorubicin (Dox) is efficiently encapsulated. The in vitro release profile shows an enhanced release of Dox at low pH (5.0) in 10 mM glutathione (GSH). The in vitro cell viability assays performed using various cell lines show that the blank hybrid micelles have no acute or intrinsic toxicity. A pH-dependent cytotoxicity is observed with the Dox-loaded micelles, especially at pH 5.0. Moreover, confocal microscopy images and flow cytometry results show the pH-dependent cellular uptake of Dox-loaded micelles. Therefore, the Dox-loaded micelles can be considered a good candidate for cancer therapy. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017A series of synthetic polymer/polypeptide block copolymers consisting of a pH-responsive polypeptide unit and a biocompatible and soluble zwitterionic polymer unit are designed. Both units are connected by a redox-responsive disulfide linkers. The new block copolymers self-assemble to form uniform micelles around 100 nm in size, and they show efficient pH/redox dual-stimuli responsive drug delivery into tumor cells.
      PubDate: 2017-04-13T09:18:11.784043-05:
      DOI: 10.1002/pola.28602
       
  • Spontaneous evolution of nanostructures by light-driven growth of micelles
           obtained from in situ nanoparticlization of conjugated polymers
    • Authors: Eun-Hye Kang; Sanghee Yang, So Young Yu, Jeongeun Kim, Tae-Lim Choi
      Abstract: To simplify processes to produce self-assembled nanostructures from polymeric materials, there have been several attempts for in situ self-assembly of block copolymers. As one of these strategies, we developed the in situ nanoparticlization of conjugated polymers (INCP) process to construct various stable nanostructures without postsynthetic treatments. To get spontaneous mesoscopic evolution of the nanostructures obtained by INCP, a new strategy utilizing a unique conformational change of the conjugated polymer is reported herein. The combination of living ring-opening olefin metathesis polymerization (ROMP) and cyclopolymerization produced block and gradient copolymers through one-pot or one-shot polymerization, which initially formed spherical micelles via INCP. Then, the core block of the micelle stiffened through a coil-to-rod conformational change by simple aging in organic solvents because of cis-to-trans isomerization of the conjugated polymer under light. Subsequently, this enhanced the π-π interaction among the cores, and eventually promoted the growth of stable nanostructures from spheres to 1D-nanocaterpillars or 2D-sheet-like architectures. This time-dependent macroscopic evolution provides deeper insight into the production of a variety of kinetically fixed nano- and mesoscale structures through INCP. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017Time-dependent macroscopic evolution of nanostructures is successfully obtained from light-driven growth of micelles. One-pot or one-shot polymerization to synthesize block and gradient copolymers initially forms spherical micelles through in situ nanoparticlization of conjugated polymers (INCP) process. Then, cis-to-trans isomerization of the conjugated polyenes occurs under light, triggering spontaneous evolution to a larger and higher dimension.
      PubDate: 2017-04-08T07:56:33.393865-05:
      DOI: 10.1002/pola.28598
       
  • Grafting polymerization of single-handed helical poly(phenyl isocyanide)s
           on graphene oxide and their application in enantioselective separation
    • Authors: Yi Xiao; Hui-Qing Wang, Hao Zhang, Zhi-Qiang Jiang, Ya-Qi Wang, Hai Li, Jun Yin, Yuan-Yuan Zhu, Zong-Quan Wu
      Abstract: We herein report a “grafting from” strategy to immobilize optically active helical poly(phenyl isocyanide)s onto graphene oxide (GO) nanosheets. After covalently bounding alkyne-Pd(II) initiator onto GO nanosheets, the designed GO/polymer composites P1@GO and P1-b-P2@GO featuring single-handed helical poly(phenyl isocyanide)s growing from GO nanosheets were prepared by sequential addition of the chiral and achiral isocyanide monomers. Post-synthetic hydrolysis rendered P1-b-P3@GO to improve the hydrophilicity. The successful covalent bonding of poly(phenyl isocyanide)s chains onto GO nanosheets was certified by several cross evidences including scan emission microscopy, atomic force microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Circular dichroism spectra proved that the chiral information was introduced through the grafted single-handed helical polymer chains successfully. In addition, the resulting GO/polymer composites were explored as a chiral additive to induce enantioselective crystallization of racemic organic molecules. Preferential formation of rod-like L-alanine crystals was induced by composites bearing right-handed helical poly(phenyl isocyanide)s. The enantiomeric excess value of the induced crystals reached 76%, displaying the potential in future applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017The optically active helical poly(phenyl isocyanide)s polymer and copolymer were functionalized to graphene oxide sheets through “grafting from” strategy. The composite materials were used as chiral inducer toward enantiomer separation
      PubDate: 2017-04-08T07:56:28.420761-05:
      DOI: 10.1002/pola.28599
       
  • Activation of alkyl halides at the Cu0 surface in SARA ATRP: An assessment
           of reaction order and surface mechanisms
    • Authors: Kyle F. Augustine; Thomas G. Ribelli, Marco Fantin, Pawel Krys, Yidan Cong, Krzysztof Matyjaszewski
      Abstract: The external order in reagents for the activation of alkyl halides by Cu0 was investigated in supplemental activator and reducing agents (SARA) ATRP. Using methyl 2-bromopropionate (MBrP) or ethyl α-bromophenylacetate (EBPA) and tris(2-(dimethylamino)ethyl)amine (Me6TREN) in DMSO and MeCN, it was determined that the rate of activation scaled with (S/V)0.9 in both solvents. For MBrP, the rate was first order with respect to [MBrP]0 until a saturation in the rate was observed around 33 and 110 mM in DMSO and MeCN, respectively. For EBPA, the reaction was also first order until a maximum rate was observed at 33 mM in DMSO, whereas an inverse order was observed for concentrations above 66 mM in MeCN. At saturated concentrations of MBrP, it was found that the rate increased linearly with respect to [Me6TREN]0 for all systems but became asymptotic with a maximum rate of 2 × 10−6 and 4 × 10−5 M s−1 in DMSO and MeCN, respectively. Model polymerizations in the absence of ligand showed slow reaction rates, indicating the necessity for ligand. The results allow more accurate modeling and understanding of SARA ATRP under a large range of initiator concentrations. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017Model studies of supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP) were conducted for the activation of alkyl halides by Cu0. Reaction orders with respect to initiators, ligand, and Cu0 were examined in acetonitrile (MeCN) and dimethyl sulfoxide (DMSO). The possible mechanisms of alkyl halide activation on the Cu0 surface were subsequently discussed. They include competitive adsorption of alkyl halides and ligands on Cu0 surface as well as ligand-assisted desorption of CuI from the surface. These findings help to understand and optimize SARA ATRP.
      PubDate: 2017-04-08T07:56:12.528064-05:
      DOI: 10.1002/pola.28585
       
  • Synthesis of highly thermostable norbornene-isoprene-1-octene terpolymer
           with titanium catalyst
    • Authors: Ryo Tanaka; Ryusei Matsuzaki, Yuushou Nakayama, Takeshi Shiono
      Abstract: Terpolymerization of norbornene (NB), isoprene (IP), and 1-octene was achieved by using fluorenylamido-ligated titanium catalyst, which showed very high activity for the copolymerization of NB and various α-olefins. The content of IP in the terpolymer was controlled by the feed ratio and reaction temperature up to 7 mol %. The incorporated IP was mainly inserted in 1,4-addition. The polymer was dissolved into common solvents such as toluene and chloroform, which enabled the preparation of a transparent film by solution casting process. The degradation temperature of the terpolymer was comparable with other cyclic olefin copolymers and the glass transition temperature (Tg) was higher than that of NB-1-octene copolymer with almost the same NB content. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017The terpolymerization of norbornene (NB), isoprene (IP), and 1-octene was investigated with a fluorenylamido-ligated titanium catalyst. The molecular weight of the terpolymer was large enough for the preparation of self-standing transparent film by solution casting process. The glass transition temperature of the terpolymer was higher than that of NB-1-octene copolymer with almost the same NB content.
      PubDate: 2017-04-08T07:56:07.603253-05:
      DOI: 10.1002/pola.28601
       
  • A “Mitsubishi emblem” tetrauclear aluminum complex containing two
           unsymmetric N2O2-ligands and a symmetric NO3-ligand as initiator for
           polymerization of rac-lactide
    • Authors: Minggang Hu; Fugui wang, Fuzhong Han, Qigang Deng, Wenhui Ma, Hailong Yan, Guohua Dong, Weiming Song
      Abstract: A novel hydroxy-, methoxy-, and phenoxy-bridge “Mitsubishi emblem” tetranuclear aluminum complex (1) is synthesized from an unsymmetric amine-pyridine-bis(phenol) N2O2-ligand (H2L1) and a symmetric amine-tris(phenol) NO3-ligand (H2L2). Two same configuration chiral nitrogen atoms are formed in the tetranuclear Al complex upon coordination of the unsymmetric tertiary amine ligand to central Al. Complex 1 initiates controlled ring-opening polymerization (ROP) of rac-lactide and afford polylactide (PLA) with narrow molecular weight distributions (Mw/Mn = 1.05–1.19). The analysis of 1H NMR spectra of the oligomer indicates that the methoxy group is the initiating group and the ring-opening polymerization of lactide follows a coordination-insertion mechanism. The Homonuclear decoupled 1H NMR spectroscopy suggests the isotactic-rich chains is preferentially formed in PLA. The study on kinetics of the ROP of lactide reveals the homopropagation rate is higher than the cross-propagation rate, which is in agreement with the observed isotactic selectivity in the ROP of rac-lactide. The stereochemistry of the polymerization was also supported by activation parameters. The introduction of unsymmetric ligand H2L1 has an effect on stereoslectivity of polymerization. This result may be of interest for the design of multinuclear metal complex catalysts containing functionalized ligands. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017A novel hydroxy-, methoxy-, and phenoxy-bridged tetanuclear “Mitsubishi emblem” aluminum complex is synthesized. The complex is capable of initiating the ring-opening polytmerization of rac-lactide to yield isotactic-rich polylactide with very narrow polydispersity indexes. The kinetic studies reveal the homopropagation rate is higher than the cross-propagation rate, and the observed isotactic selectivity in the polymerization of rac-lactide is also supported by activation parameters.
      PubDate: 2017-04-08T07:56:05.790776-05:
      DOI: 10.1002/pola.28597
       
  • Developments in synthesis, characterization, and self-assembly of
           polycarbodiimide systems
    • Authors: Nimmy R. Mammoottil; James F. Reuther, Dumindika A. Siriwardane, Oleg V. Kulikov, Bruce M. Novak
      Abstract: Described herein is a comprehensive survey on the most recent advancements in polycarbodiimide synthetic methodologies, structure determination, property design, and self-assembly. In particular, the 15N-isotopic enrichment of polycarbodiimides is detailed along with the use of 15N NMR to identify the regioregularity and mechanism of chiroptical switching in polycarbodiimides. Furthermore, the new Ni(II) mediated “living” polymerization is explained along with its utilization in the incorporation of polycarbodiimides into block copolymers, graft copolymers, and star polymers. Finally, we review the recent discoveries focusing on the highly tunable self-assembly behaviors of polycarbodiimide homopolymers and copolymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017This highlight focuses on the most recent advancements in polycarbodiimide chemistry. Most notably, it describes the newest developments in microstructure determination, property design, synthetic methodology, and self-assembly of polycarbodiimides.
      PubDate: 2017-03-27T21:05:52.241977-05:
      DOI: 10.1002/pola.28583
       
  • Poly(hexamethylene guanidine)-based hydrogels with long lasting
           antimicrobial activity and low toxicity
    • Authors: Chao Zhang; Zhimin Ying, Qiaojie Luo, Hong Du, Ying Wang, Kai Zhang, Shigui Yan, Xiaodong Li, Zhiquan Shen, Weipu Zhu
      Abstract: Long lasting antimicrobial activity and low toxicity are essentials for hydrogels in biomedicine. However, most reported hydrogels cannot combine these characteristics. In this work, poly (hexamethylene guanidine) hydrochloride (PHMG), a cheap cationic polymer with two terminal amino groups, was first modified with methacrylic anhydride to give PHMG dimethacrylamide (PHMGDMAAm), which was further used to prepare hydrogels with acrylamide (AAm) under ultraviolet irradiation in the presence of α-ketoglutaric acid (α-KGA) as photoinitiator in aqueous medium. The resultant hydrogels showed strong antibacterial activity against both Gram-negative and Gram-positive bacteria due to the PHMG segments in the hydrogel backbone. Moreover, the antimicrobial activity of the hydrogels did not decrease significantly after being soaked in water for one month and washed by water frequently for many times. Hemolysis and cytotoxicity assays demonstrated the excellent biocompatibility of the PHMG-PAAm hydrogels. This kind of low cost cationic hydrogels with long lasting antimicrobial activity and low toxicity is expected to have potential applications in biomedicine. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017PHMG-PAAm hydrogels with cationic PHMG segment as backbone were facilely prepared by simple radical polymerization under UV irradiation in aqueous medium. These hydrogels showed long lasting antimicrobial activity and good biocompatibility, which have great potential as biomaterials in clinical applications.
      PubDate: 2017-03-25T10:05:47.904951-05:
      DOI: 10.1002/pola.28581
       
  • Block copolymer micelles with enzyme molecules at the interfaces
    • Authors: Jinchuan Liu; Xiaotian Ji, Hanying Zhao
      Abstract: This research provides an efficient method for the fabrication of hybrid micelles with enzyme molecules at the interfaces. Amphiphilic block copolymer is synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization, and thiol-modified porcine pancreatic lipase (PPL-SH) is obtained by treatment of native PPL with Traut's reagent. PPL-SH is conjugated to the block copolymer chains by thiol-disulfide exchange reaction. In phosphate buffered saline, the bioconjugate self-assembles into micelles with enzyme molecules at the interfaces between hydrophobic cores and hydrophilic coronae. The bioactivity of the enzyme molecules on the micelles are compared with the native enzyme. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017Micelles with porcine pancreatic lipase molecules at the interfaces between hydrophobic cores and hydrophilic coronae are prepared in this research. The enzyme molecules show bioactivity in the catalysis of hydrolysis reactions of para-nitrophenyl palmitate.
      PubDate: 2017-03-25T10:05:42.657672-05:
      DOI: 10.1002/pola.28587
       
  • One-pot synthesis of soluble and fluorescent aliphatic hyperbranched
           poly(amide-imide) with solvent-dependent emission
    • Authors: Rong-Rong Wang; Jun-Jie Yan, Run-Lin Yang, Dong-Hui Pan, Wen Li, Yu-Ping Xu, Li-Zhen Wang, Xin-Yu Wang, Min Yang
      Abstract: Aliphatic hyperbranched poly(amide-imide) was facilely prepared by employing a functional thiolactone-maleimide monomer. Highly efficient, selective and quantitative properties of amine-maleimide Michael addition and aminolysis of a thiolactone guaranteed the generation of an ABB' thiol-yne intermediate without side products, followed by consecutive thiol-yne click reaction in one-pot. The hyperbranched structure of the poly(amide-imide) was confirmed by NMR spectroscopy and triple-detector GPC/SEC analysis. Additionally, due to the presence of aminosuccinimide fluorophores and intrinsic physical property of hyperbranched polymers, this aliphatic hyperbranched poly(amide-imide) possessed solvent-dependent emission and presented good solubility in various organic solvents. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017Fluorescent aliphatic hyperbranched poly(amide-imide) (HPAI) was facilely synthesized by sequential amine-maleimide Michael addition, aminolysis of thiolactone and thiol-yne click reaction from a thiolactone-maleimide functional monomer. Moreover, the HPAI possessed good solubility in many organic solvents and presented solvent-dependent emission.
      PubDate: 2017-03-25T10:05:37.191324-05:
      DOI: 10.1002/pola.28588
       
  • Degradation of poly(β-amino ester) gels in alcohols through
           transesterification: Method to conjugate drugs to polymer matrices
    • Authors: Prachi Gupta; Caroline Lacerda, Vinod S. Patil, Dipti Biswal, Paritosh Wattamwar, J. Zach Hilt, Thomas D. Dziubla
      Abstract: Poly(β amino ester) (PβAE) polymers have received growing attention in the literature, owing to their ease of synthesis, versatile co-monomer selection, and highly tunable degradation kinetics. As such, they have shown extensive potential in many biomedical applications as well. In this work, it is demonstrated for the first time that PβAE polymers containing primary and secondary amine groups can undergo degradation by primary alcohols via transesterification mechanism. While this work emphasizes an important aspect of solvent compatibility of these networks, it also represents an interesting, simple mechanism for post synthesis drug incorporation, with riboflavin conjugation being demonstrated as a model compound. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017Poly(β-amino esters) polymers, a promising class of biomaterials, were found to degrade in alcohol via transesterification. This effect was found to be dependent upon the presence of free amine groups in the polymer backbone. Using this reactivity, it was also shown it is possible to modify the gels with alcohol containing drug molecules, creating a pro-drug gel system.
      PubDate: 2017-03-25T01:30:34.212787-05:
      DOI: 10.1002/pola.28579
       
  • Tailored molybdenum imido alkylidene N-heterocyclic carbene complexes as
           latent catalysts for the polymerization of dicyclopentadiene
    • Authors: Julia Beerhues; Suman Sen, Roman Schowner, Gergely Mate Nagy, Dongren Wang, Michael R. Buchmeiser
      Abstract: Three novel molybdenum imido alkylidene N-heterocyclic carbene (NHC) pre-catalysts, that is, Mo(N-t-Bu)(1-(2,6-diisopropylphenyl)-3-isopropyl-4-phenyl-1H-1,2,3-triazol-5-ylidene)(CHCMe2Ph)(OTf)2 (I1, OTf = CF3SO3), Mo(N-t-Bu)(1-(2,6-diisopropylphenyl)-3-isopropyl-4-phenyl-1H-1,2,3-triazol-5-ylidene)(CHCMe2Ph)(OTf)(t-BuO) (I2) and Mo(N-2,6-Me2-C6H3)(1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene)(CHCMe2Ph)(OTf)2 (I3) are presented. Compared to complexes based on imidazol-2-ylidenes or imidazolin-2-ylidenes, (1-(2,6-diisopropylphenyl)-3-isopropyl-4-phenyl-1H-1,2,3-triazol-5-ylidene) used in precatalysts I1 and I2 exerts a comparably strong trans effect to the triflate groups trans to the NHC, while (1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene) used in I3 has a weaker trans effect on the triflate. In combination with a suitable second anionic ligand at molybdenum, that is, OTf, t-BuO, compounds I1–I3 require higher temperatures to become active and can thus be used as truly room temperature latent pre-catalysts, even for a highly reactive monomer such as dicyclopentadiene (DCPD). When used as latent precatalysts, I1–I3 offer access to poly-DCPD with different degrees of cross-linking and glass-transition temperatures (Tg). © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017Molybdenum imido alkylidene N-heterocyclic carbene (NHC) complexes as room temperature-latent precatalysts for the ring-opening metathesis polymerization (ROMP) of dicyclopentadiene are described. Precatalysts are tailored by combining strongly and weakly σ-donating NHCs with suitable anionic ligands at molybdenum such as triflate and t-butoxide. All precatalysts prepared offer access to cross-linked poly-DCPD though with different degrees of cross-linking and glass-transition temperatures.
      PubDate: 2017-03-25T01:30:29.020446-05:
      DOI: 10.1002/pola.28578
       
  • Chemical warfare simulant-responsive polymer nanocomposites: Synthesis and
           evaluation
    • Authors: Sheng-Chun Sha; Rong Zhu, Myles B. Herbert, Julia A. Kalow, Timothy M. Swager
      Abstract: Nanomaterials that undergo a physical change upon chemical warfare agent (CWA) exposure can potentially be used in detectors to warn soldiers of their presence or in fabrics to provide on-demand protection. In this study, hybrid nanoparticles (NPs) were prepared by grafting a CWA-responsive polymer from a silicon dioxide (SiO2) surface using ring opening metathesis polymerization; the covalent functionalization of the polymers on the NP surface was confirmed by gel permeation chromatography, dynamic light scattering, and transmission electron microscopy analysis. The polymer-grafted SiO2 NPs were found to undergo a pronounced decrease (approximately 200 nm) in their hydrodynamic radius upon exposure to CWA simulants trifluoroacetic acid and diethyl chlorophosphate in toluene. This decrease in hydrodynamic radius is attributed to the electrophile-mediated ionization of the triarylmethanol responsive unit and represents a rare example of polycation formation leading to polymer chain collapse. We have ascribed this ionization-induced collapse to the formation of a favorable stacking interaction between the planar triarylcations. These studies have important implications for the development of breathable fabrics that can provide on-demand protection for soldiers in combat situations. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017Chemical warfare agents continue to post a threat to civilians and military personnel in conflict zones. As a step toward a breathable hybrid fabric that provides on-demand protection against these agents, the authors have synthesized a triarylmethanol-containing responsive polymer-substituted nanoparticle using surface-initiated ring-opening metathesis polymerization. Using this nanocomposite as a platform demonstrates a tunable chain collapsing response upon exposure to agent simulants, which is the key to the proposed protecting scheme.
      PubDate: 2017-03-23T22:50:33.334841-05:
      DOI: 10.1002/pola.28580
       
  • Synthesis of poly(vinyl alcohol-graft-hyperbranched glycerol)
    • Authors: Peter A. King; Ezat Khosravi, Osama M. Musa
      Abstract: We report the first example of grafting hyperbranched polyglycerol onto poly(vinyl alcohol) via ring-opening polymerisation of glycidol to prepare poly(vinyl alcohol-graft-hyperbranched glycerol) (P[(VA)-g-(hPG)]). The effects of catalyst, molecular weight of PVA, reaction temperature, water content, moles of reagent, and addition time of reagent were also investigated. P[(VA)-g-(hPG)] with various mole fractions of hPG were prepared and the degrees of substitution and branching were determined. P[(VA)-g-(hPG)] displayed decreased degree of crystallinity and also increased solubility in water, compared to PVA. P[(VA)-g-(hPG)] is shown to be a superior hair styling polymer with a curl retention value of 85% after 4 h. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017The authors report the first example of grafting hyperbranched polyglycerol onto poly(vinyl alcohol) via ring-opening polymerisation of glycidol to prepare poly(vinyl alcohol-graft-hyperbranched glycerol) (P[(VA)-g-(hPG)]). P[(VA)-g-(hPG)] displayed decreased degree of crystallinity and also increased solubility in water, compared to PVA. P[(VA)-g-(hPG)] is shown to be a superior hair styling polymer with a curl retention value of 85% after 4 h.Fx
      PubDate: 2017-03-23T22:50:27.325749-05:
      DOI: 10.1002/pola.28582
       
  • Facile synthesis of self-healing gel via magnetocaloric bottom-ignited
           frontal polymerization
    • Authors: Xiang-Yun Du; Si-Si Liu, Cai-Feng Wang, Guan Wu, Su Chen
      Abstract: A series of the self-healing gels facilely fabricated by VI (N-vinyl imidazole) and MAH-β-CD (β-cyclodextrin grafted vinyl carboxylic acid groups) via bottom-ignited frontal polymerization (BIFP) initiated by magnetocaloric effect. Once ignited the bottom phase, the heat upward propagates to generate the “front” in the upper phase. Then, no further energy is added to maintain the reaction and the whole polymerization process experiences within minutes. In this system, the dependence of frontal velocity and temperature, along with morphology, swelling capacity, mechanical property, and self-healing efficiency, on the preparation parameters is investigated. Interestingly, the gels show good swelling capacity in the organic solvent, comparatively almost no absorption in water. Moreover, the as-prepared gels exhibit excellent auto-healing properties without any external stimuli at ambient temperature. The healed sample possesses 97% recovery of its tensile strength after 8 h healing time, which relies largely on the host–guest interaction between VI and MAH-β-CD. The results demonstrate that FP can be utilized as an efficient and energy-saving method to synthesize self-healing supramolecular gels. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017A new fast and efficient mode is designed to fabricate a series of polymer gels by VI (N-vinyl imidazole) and MAH-β-CD (β-cyclodextrin grafted vinyl carboxylic acid groups), BA (butyl acrylate), and Am (acrylamide) via magnetocaloric bottom-ignited frontal polymerization (BIFP). A stable “front” was observed in polymerization process without occurrence of “fingering.” The as-prepared samples exhibit excellent self-healing ability without any external stimuli at ambient temperature, taken advantage of host–guest interaction between VI and MAH-β-CD. The healed sample performs 97% recovery of its tensile strength after 8 h healing time.
      PubDate: 2017-03-23T04:45:54.121877-05:
      DOI: 10.1002/pola.28521
       
  • Established and emerging strategies for polymer chain-end modification
    • Authors: David J. Lunn; Emre H. Discekici, Javier Read de Alaniz, Will R. Gutekunst, Craig J. Hawker
      Abstract: The development of “controlled” and “living” polymerization processes with high end-group fidelity has enabled an unprecedented range of polymeric materials with specific chain-end functionality to be prepared. This highlight provides an overview of available strategies and evaluation of recent approaches for the chain-end functionalization of polymers prepared through controlled chain-growth polymerizations. As a tribute to Professor Robert B. Grubbs on the occasion of his 75th birthday, we also take this opportunity to highlight methods for the chain-end modification of polymers prepared by ring-opening metathesis polymerization within the broader context of functional group tolerant, living polymerizations. Finally, we focus attention toward new directions in polymer chain-end modifications, describing existing gaps in current strategies, and detailing recently reported protocols that show significant improvements over traditional methods. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017Overview of available strategies for the chain-end functionalization of polymers prepared via the most widely used chain-growth polymerizations, including controlled radical polymerizations, ring-open metathesis polymerization and several anionic and transition-metal mediated processes. Common methods for the functionalization of polymer chain-ends, existing gaps in current strategies, and recently reported protocols that show significant improvements over traditional methods are highlighted.
      PubDate: 2017-03-22T12:50:29.22536-05:0
      DOI: 10.1002/pola.28575
       
  • Double-stranded ladderphanes with C2-symmetric planar chiral ferrocene
           linkers
    • Authors: Jun Xu; Ze Zhang, Yi-Hung Liu, Qingxiang Guo, Guan-Wu Wang, Guoqiao Lai, Tien-Yau Luh
      Abstract: Eight ladderphanes with C2-symmetric planar chiral ferrocene linkers are synthesized by ring opening metathesis polymerization of bisnorbornene monomers using Grubbs-I catalyst. The aminobenzoate in both monomers and polymers shows absorption maximum around 320 nm. Both monomers and polymers are Circular dichroism (CD) active. Little enhancements of CD profiles around 320 nm are observed for ladderphanes having chiral chloro- or phenyl-substituted ferrocene linkers. However, ladderphanes with a phenyl substituent on the cyclopendienyl ring exhibits enhancement of CD curves aound 240–300 nm. The congested phenyl moieties in adjacent linkers in this polymer might be well oriented such that interactions between these aromatic substituents on different monomeric units might provoke the enhancement of the CD curves in this region. When the methyl-substituted cyclopendienyl ligand is used for chiral ferrocene linkers, the ladderphanes exhibit two-fold enhancement of CD spectrum around 320 nm. This enhancement is further increased when the cyclopentadienyl ligand contains an additional phenyl substituent, owing to exciton coupling between aminobenzoate moieties in adjacent monomeric units. Moreover, the intensity of the CD curves in the region of 240–300 nm is significantly increased. These results suggest that the later polymer may adopt a posible helical structure. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017.Double-stranded ladderphanes with C2-symmetric planar chiral ferrocene linkers are synthesized by ring opening metathesis polymerization using Grubbs-I catalyst. Significant CD enhancement is observed when the cyclopentadienyl ligands in the ferrocene linker have methyl and phenyl substituents at C2 and C5 positions.
      PubDate: 2017-03-21T06:11:44.864139-05:
      DOI: 10.1002/pola.28572
       
  • Polymerization of optically active disubstituted acetylene monomers by Pd
           catalyst bearing bulky phosphine ligand
    • Authors: Yuta Goto; Yu Miyagi, Natsuhiro Sano, Fumio Sanda
      Abstract: Chloro- and aryl-substituted acetylene monomers having an optically active group were polymerized by a Pd catalyst [(tBu3P)PdMeCl] bearing a bulky phosphine ligand, and by MoCl5 for comparison. The corresponding disubstituted acetylene polymers with Mn's = 2000–19,500 and 6900–10,800 were obtained in 29–83% and 11–62% yields when the Pd and Mo catalysts were used, respectively. The formation of polyacetylenes, poly[(R)-1p], poly[(R)-1m], and poly[(S)-2p] were confirmed by SEC and the presence of a Raman scattering peak based on the alternating double bonds of the main chain. Pd-based poly[(R)-1m] exhibited CD signals around 350 nm assignable to a certain secondary structure, while Mo-based poly[(R)-1m] did not. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017.Chloro- and aryl-substituted acetylene monomers having an optically active group were polymerized by [(tBu3P)PdMeCl] as a catalyst to obtain the corresponding disubstituted acetylene polymers with Mn's of 2000–19,500 in 29–83%. The polymer having meta-substituted phenyl groups exhibited CD signals assignable to a certain secondary structure and liquid crystalline properties.
      PubDate: 2017-03-21T06:11:04.175838-05:
      DOI: 10.1002/pola.28573
       
  • Synthesis of photoactive single-chain folded polymeric nanoparticles via
           combination of radical polymerization techniques and Menschutkin click
           chemistry
    • Authors: Secil Babaoglu; Demet Karaca Balta, Gokhan Temel
      Abstract: This contribution reports that synthesis of polystyrene based photoactive polymeric nanoparticles by radical copolymerization and Menschutkin Chemistry methodology. In the first step, poly(styrene-co-chloromethyl styrene) was achieved by thermally initiated radical copolymerizations and subsequently copolymers were reacted to commercially available Type II photoiniator (Michler's ketone) in dilute condition in order to achieve intramolecular crosslinked polymeric nanoparticles. After the characterization studies, polymeric nanoparticles were used for free radical photopolymerization of methacrylic formulations to determine the initiation efficiency. Upon UV irradiation, resulting polymeric nanoparticle lost its globular structure by releasing benzophenone part and transformed into linear copolymer analogue. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017Benzophenone containing single chain polymeric nanoparticles are synthesized and employed for free radical photopolymerization. Photoactive polymeric nanoparticle releases benzophenone moieties and transforms to linear precursor under UV irradiation. Released photoinitiator efficiently initiates the free radical polymerization of methyl methacrylate.
      PubDate: 2017-03-21T06:10:54.080672-05:
      DOI: 10.1002/pola.28571
       
  • Solvent effects on the intramolecular charge transfer character of
           N,N-diaryl dihydrophenazine catalysts for organocatalyzed atom transfer
           radical polymerization
    • Authors: Matthew D. Ryan; Jordan C. Theriot, Chern-Hooi Lim, Haishen Yang, Andrew G. Lockwood, Nathaniel G. Garrison, Sarah R. Lincoln, Charles B. Musgrave, Garret M. Miyake
      Abstract: The nature of intramolecular charge transfer (CT) of N,N-diaryl dihydrophenazine photocatalysts (PCs) in different solvents is explored in context of their performance in organocatalyzed atom transfer radical polymerization (O-ATRP). PCs having a computationally predicted lowest energy excited state exhibiting CT character can operate a highly controlled O-ATRP in a wide range of solvent polarities, from non-polar hexanes to highly polar N,N-dimethylacetamide. For PCs having a computationally predicted lowest energy excited state not possessing CT character, their ability to operate a controlled O-ATRP is decreased. This study confirms the importance of CT character in the excited state for N,N-diaryl dihydrophenazine PCs, and a deeper understanding of the activity of CT PCs has enabled the synthesis of polymers of low dispersity (
      PubDate: 2017-03-16T19:16:08.181966-05:
      DOI: 10.1002/pola.28574
       
  • Recyclable polybutadiene elastomer based on dynamic imine bond
    • Authors: Huan Zhang; Dong Wang, Wenxing Liu, Pengchong Li, Jiajian Liu, Chenyang Liu, Jiawei Zhang, Ning Zhao, Jian Xu
      Abstract: Catalyst-free recyclable polybutadiene (PB) elastomer cross-linked by dynamic imine bonds is prepared by the reaction between amine functionalized PB and aldehyde cross-linkers. The dynamic nature of imine bond is investigated by rheometry and creep-recovery experiments. The cross-linking degrees are regulated by incorporating different amount of aldehyde, and their influence on the cross-linked elastomers is investigated in detail. The temperature-induced imine exchange reactions enable recycling of the cross-linked PB elastomers and their mechanical properties are almost unchanged after several cycles. It is important to note that the elastomers also show excellent solvent resistance even at high temperature. The good mechanical properties, solvent resistance and recycling ability of the resultant PB elastomer demonstrate the superiority of the imine bonds in the design of recyclable polymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017Thermoreversible PB elastomers with good mechanical properties and solvent resistance cross-linked by imine bonds were demonstrated. More importantly, the as-prepared elastomer can be thermally recycled by taking advantage of the dynamic nature of imine bond.
      PubDate: 2017-03-16T19:16:05.274908-05:
      DOI: 10.1002/pola.28577
       
  • Functional polyisobutylenes via electrophilic cleavage/alkylation
    • Authors: C. Garrett Campbell; Robson F. Storey
      Abstract: Lewis-acid catalyzed degradation of poly(isobutylene-co-isoprene) (butyl rubber) in the presence of an alkoxybenzene compound was studied as a new route toward low molecular weight multifunctional polyisobutylenes. Simultaneous cleavage and functionalization of butyl rubber was conducted at −70 °C and −40 °C under TiCl4 or AlCl3 catalysis in 60/40 hexane/methylene chloride cosolvents in the presence of (3-bromopropoxy)benzene (BPB) for various times up to 24 h. The butyl rubber (EXXON™ Butyl 365) possessed Mn = 1.91 × 105 g/mol, PDI = 1.66 (GPC/MALLS), and 2.30 mol % isoprene units (nearly exclusively trans−1,4). At −70 °C with TiCl4, molecular weight was reduced to various values within the range 7 to 11 × 103 g/mol depending on conditions; lower BPB concentration produced lower molecular weight. However, the ratio of isobutylene repeat units to BPB units (IB/Q) remained constant at about 43:1, which is approximately the same as the ratio of isobutylene to isoprene repeat units (IB/IP) in the starting butyl rubber (42.5:1). At −40 °C with TiCl4, molecular weight was reduced to about 5 × 103 g/mol, and IB/Q was reduced below IB/IP, indicating nearly a difunctional telechelic structure. AlCl3 was a more active catalyst and produced results similar to TiCl4 at −40 °C, even when used at seven times lower concentration. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017Electrophilic cleavage/alkylation of poly(isobutylene-co-isoprene) in the presence of a Lewis acid, a protic acid, and alkoxybenzene compound was studied as a new route toward low molecular weight multifunctional polyisobutylenes. The reaction represents a variation on Friedel-Crafts alkylation chemistry, in which a bulky carbenium ion undergoes β-cleavage to yield two smaller fragments that readily undergo alkylation.
      PubDate: 2017-03-16T19:15:58.818612-05:
      DOI: 10.1002/pola.28570
       
  • Hydrolysis of aromatic polyurethane in water under high pressure of CO2
    • Authors: Suguru Motokucho; Akito Yamaguchi, Yu Nakayama, Hiroshi Morikawa, Hisayuki Nakatani
      Abstract: We have demonstrated a hydrolysis reaction of polyurethane (PU) under high pressure of carbon dioxide (CO2) in water. We employed the PU sample, poly(methylene bis-(1,4-phenylene)hexamethylene dicarbamate), denoted as M-PU, which was synthesized from 4,4′-diphenyl methane diisocyanate and 1,4-butane diol (BD). The optimum hydrolysis reaction condition was 190 °C under CO2 pressures over 4.1 MPa in water medium, and 93% hydrolysis of M-PU was achieved. After the reaction, the water-soluble parts were obtained, and isolated by column chromatography. The isolated products were 4,4′-methylenedianiline (MDA) and 1,4-butane diol (BD), which were components of repeating unit of M-PU. In addition, the hydrolysis reaction gave no byproduct. This hydrolysis under high pressure of CO2 with water is a reaction by which M-PU is selectively hydrolyzed into MDA and BD by cleaving urethane linkage. Moreover, the resulting hydrolyzed products were easily obtained by evaporation of aqueous layer after the reaction, indicating an efficient chemical recycling of PU was achieved. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017In this article, a hydrolysis reaction of polyurethane (M-PU) under high pressure of carbon dioxide (CO2) in water is demonstrated. The optimum hydrolysis reaction condition was 190 °C under CO2 pressures over 4.1 MPa in water medium, and 93% hydrolysis of M-PU was achieved. This hydrolysis under high pressure of CO2 with water is a reaction by which M-PU is selectively hydrolyzed into consisted chemicals of repeating units of M-PU by cleaving urethane linkage.
      PubDate: 2017-03-16T19:15:55.482488-05:
      DOI: 10.1002/pola.28576
       
  • Balancing high thermal stability with high activity in
           diaryliminoacenaphthene-nickel(II) catalysts for ethylene polymerization
    • Authors: Yanjun Chen; Shizhen Du, Chuanbing Huang, Gregory A. Solan, Xiang Hao, Wen-Hua Sun
      Abstract: The N,N-diaryliminoacenaphthenes, 1,2-[2,4-{(4-FC6H4)2CH}2-6-MeC6H4N]2-C2C10H6 (L1) and 1-[2,4-{(4-FC6H4)2CH}2-6-MeC6H4N]-2-(ArN)C2C10H6 (Ar = 2,6-Me2C6H3 L2, 2,6-Et2C6H3 L3, 2,6-i-Pr2C6H3 L4, 2,4,6-Me3C6H2 L5, 2,6-Et2-4-MeC6H2 L6), incorporating at least one N−2,4-bis(difluoro benzhydryl)-6-methylphenyl group, have been synthesized and fully characterized. Interaction of L1–L6 with (DME)NiBr2 (DME = 1,2-dimethoxyethane) generates the corresponding nickel(II) bromide N,N-chelates, LNiBr2 (1–6), in high yield. The molecular structures of 3 and 6 reveal distorted tetrahedral geometries at nickel with the ortho-substituted difluorobenzhydryl group providing enhanced steric protection to only one side of the metal center. On activation with various aluminum alkyl co-catalysts, such as methylaluminoxane (MAO) or Et2AlCl, 1–6 displayed outstanding activity toward ethylene polymerization (up to 1.02 × 107 g of PE (mol of Ni)−1 h−1). Notably 1, bearing equivalent fluorobenzhydryl-substituted N-aryl groups, was able in the presence of Et2AlCl to couple high activity with exceptional thermal stability generating high molecular weight branched polyethylenes at temperatures as high as 100 °C. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017N,N-Diaryliminoacenaphthene-nickel(II) bromide complexes, on activation with MAO or Et2AlCl, display outstanding activity toward ethylene polymerization (up to 1.02 × 107 g of PE (mol of Ni)−1 h−1), exceptional thermal stability and generate high molecular weight branched polyethylene at temperatures as high as 100 °C.
      PubDate: 2017-03-13T02:15:59.898753-05:
      DOI: 10.1002/pola.28562
       
  • Synthesis and memory characteristics of highly organo-soluble
           hyperbranched polyimides with various electron acceptors
    • Authors: Ying Song; Hongyan Yao, Haiwei Tan, Shiyang Zhu, Bo Dong, Shaowei Guan, Huiling Liu
      Abstract: A series of hyperbranched polyimides (HBPIs) were synthesized by reacting a triamine monomer N,N′,N″-tris(4-methoxyphenyl)-N,N′,N″-tris(4-phenylamino)−1,3,5-benzenetriamine with various dianhydrides such as oxydiphthalic dianhydride (ODPA), 3,3′,4,4′-diphenylsulfonetetracarboxylic dianhydride (DSDA), 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), and pyromellitic dianhydride (PMDA). The hyperbranched polyimide (6FHBPI) using 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) as dianhydride monomer was also added into the discussion. All the hyperbranched polyimides exhibited excellent organo-solubility and high thermal stability. Memory devices with a sandwiched structure of indium tin oxide (ITO)/HBPI/Al were constructed by using these HBPIs as the active layers. All these HBPIs based memory devices exhibited favorable memory performances, with switching voltages between −1.3 V and −2.5 V, ON/OFF current ratios up to 107 and retention times long to 104 s. Tunable memory characteristics from electrical insulator to volatile memory, and then to nonvolatile memory were obtained by adjusting the electron acceptors of these HBPIs. Molecular simulation results suggested that the electron affinity and the dipole moment of these HBPIs were responsible for the conversion of the memory characteristics. With the electron affinity and dipole moment of these HBPIs increasing, the memory characteristics turned from volatile to nonvolatile. The present study suggested that tunable memory performance could be achieved through adjusting the acceptor moieties of the hyperbranched polyimides. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017Tunable memory characteristics from electrical insulator to volatile memory, and then to nonvolatile memory could be obtained by adjusting the electron acceptors of these HBPIs.
      PubDate: 2017-03-11T01:20:37.393017-05:
      DOI: 10.1002/pola.28550
       
  • Preparation of polyHIPE via CuAAC “click” chemistry and its
           application as a highly efficient adsorbent of Cu(II) ions
    • Authors: Haiyong Zhang; Yun Zhu, Jianding Chen, Shengmiao Zhang
      Abstract: A hydrophilic emulsion-templated porous polymer (polyHIPE) is synthesized by CuAAC “click” chemistry. Herein, a 4,4′-diazidostilbene-2,2′-disulfonic acid disodium salt-4H2O (DAS) and tripropargylamine in the mixture of water and N,N-dimethylformamide solution is used as external phase of the high internal phase emulsion template, and paraffin liquid is involved as the internal phase. The resulting polyHIPE has a well-defined interconnected pore structure, which could be tailored by changing preparation parameters, such as reagent content, internal phase volume fraction, and surfactant concentration. Thermal analysis shows that the polyHIPE is stable under 180 °C. Owing to the presence of a large number of sodium sulfonate groups from the reagent DAS and the triazoles groups produced in the reaction, the polyHIPE is proved to be a highly efficient adsorbent of heavy metal ion (i.e., up to 52 mg/g for Cu(II) ions) in water. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017A hydrophilic emulsion-templated porous polymer was synthesized by CuAAC “click” chemistry, and this polymer was proved to be a highly efficient adsorbent of heavy metal ion (i.e., Cu(II) ions) in water.
      PubDate: 2017-03-07T00:20:51.900153-05:
      DOI: 10.1002/pola.28548
       
  • Enolesters as chain end-functionalizing agents for the living ring opening
           metathesis polymerization
    • Authors: Peng Liu; Mohammad Yasir, Helena Kurzen, Nils Hanik, Mark Schäfer, Andreas F.M. Kilbinger
      Abstract: Functional enolethers have previously been used to introduce functional end groups at the chain end of ruthenium carbene complex initiated living ring opening metathesis polymers. Here, we investigated whether the weaker π-donating enolesters could equally be used in regio selective reactions with ruthenium carbene complexes and thus as polymer end-functionalization reagents. Enolesters such as vinyl acetate, butenyl acetate, 3-(4-(tert-butoxy)phenyl)propenyl acetate and 6-(((benzyloxy)carbonyl)amino)hex-1-en-1-yl acetate were used as living ROMP terminating agents. All gave the expected end groups proving that enolesters are synthetically easily accessible targets for living ROMP end-functionalization. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017They are synthetically readily accessible from functional aldehydes. In a terminal olefin metathesis reaction step they form ruthenium acyl Fischer-carbenes and transfer the functional group to the polymer chain end.
      PubDate: 2017-01-24T23:50:50.667888-05:
      DOI: 10.1002/pola.28468
       
  • Issue Information
    • Pages: 1963 - 1963
      PubDate: 2017-05-03T02:32:26.869415-05:
      DOI: 10.1002/pola.28316
       
  • Grafted copolymer micelles with pH triggered charge reversibility for
           efficient doxorubicin delivery
    • Authors: Shaohua Wu; Liuchun Zheng, Chuncheng Li, Yaonan Xiao, Shuaidong Huo, Bo Zhang
      Pages: 2036 - 2046
      Abstract: The instability and premature charge reversal at pH 7.4 have become the major limitations of charge-reversal delivery systems. To address this problem, graft copolymer of poly(butylene succinate)-g-cysteamine-bi-poly(ethylene glycol) (PBS-g-CS-bi-PEG, bi = benzoic imine bond) was designed and synthesized through facile thiol-ene click reaction and subsequent Schiff's base reaction. Then, PBS-g-CS-bi-PEG and carboxyl-functionalized polyester of poly(butylene succinate)-g-3-mercaptopropionic acid (PBS-g-MPA) co-assemble in aqueous solution to give PEG shell-sheddable charge-reversal micelles with sizes of 85–103 nm and low polydispersity of 0.11–0.12. Interestingly, the PBS-g-MPA/CS-bi-PEG micelles could sensitively and arbitrarily switch their surface charges between negative and positive status in response to pH fluctuation via reversible protonation and deprotonation of carboxyl and amino groups, which endows the desired stability of co-assembly micelles either during long-term storage or under physiological conditions. Doxorubicin (DOX) was loaded into PBS-g-MPA/CS-bi-PEG micelles with a high drug-loading content of 10.2% and entrapment efficiency of 68% as a result of electrostatic attraction. In vitro release studies revealed that less than 25% of DOX was released within 24 h in the environment mimicking the physiological condition, whereas up to 81% of DOX was released in 24 h under weak-acid condition resembling microenvironment in endosome/lysosome. In vitro cytotoxicity study suggested that blank PBS-g-MPA/CS-bi-PEG micelles possessed excellent biocompatibility, while DOX-loaded PBS-g-MPA/CS-bi-PEG micelles showed significant cytotoxicity with half-maximal inhibitory concentration (IC50) of 1.55–1.67 μg DOX equiv/mL. This study provides a facile and effective approach for the preparation of novel charge-reversal micelles with switchable charges and excellent biocompatibility, which are highly promising to be used as safe nanocarriers for efficient intracellular drug delivery. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2036–2046A new kind of charge-reversal micelle with well-balanced stability, which can switch its surface charges between negative and positive status with high reversibility, was designed and prepared.
      PubDate: 2017-05-03T02:32:27.412311-05:
      DOI: 10.1002/pola.28586
       
 
 
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