Journal of Polymer Science Part A: Polymer Chemistry

Cover image for Vol. 43 Issue 22

15 November 2005

Volume 43, Issue 22

Pages 5347–5721

  1. Highlights

    1. Top of page
    2. Highlights
    3. Articles
    4. Rapid Communications
    1. You have free access to this content
      Macromolecular design via reversible addition–fragmentation chain transfer (RAFT)/xanthates (MADIX) polymerization (pages 5347–5393)

      Sébastien Perrier and Pittaya Takolpuckdee

      Version of Record online: 5 OCT 2005 | DOI: 10.1002/pola.20986

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      This review highlights the progress made in reversible addition fragmentation chain transfer (RAFT) and macromolecular design via the interchange of xanthates (MADIX)polymerization since their first report in 1998. It addresses the mechanism and kinetics of the process, examines the various components of the system and the polymerization conditions, and gives an account of the wide range of monomers that have been polymerized and the various polymericarchitectures that have been produced. The review shows that the process is now opening to a wider scientific community, as a synthetic tool for the production of functional macromolecules and materials.

    2. You have free access to this content
      Kinetics and mechanisms in carbocationic polymerization: The quest for true rate constants (pages 5394–5413)

      Judit E. Puskas, Sam W. P. Chan, Kimberley B. McAuley, Sohel Shaikh and Gabor Kaszas

      Version of Record online: 29 SEP 2005 | DOI: 10.1002/pola.21011

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      This article offers a critical review of published kinetic data and mechanistic interpretations of carbocationic polymerizations. With the 2,4,6-trimethylstyrene/trimethylstyryl chloride/BCl3/CH2Cl2/−70°C system as a case study, it is shown that parameter estimation from experimental data with the Predici simulation package and the alternative mechanism in the scheme shown to the right yields a propagation rate constant of 1.01 × 107 L mol−1 s−1, as predicted by Mayr's linear free energy relationship. This model gives the best fit for the experimental molecular weight distribution data. A comparison of apparent negative activation enthalpies reported by various laboratories for living isobutylene polymerization seems to support the TiCl4 order shifting between one and two and the strong influence of electron-pair donors.

  2. Articles

    1. Top of page
    2. Highlights
    3. Articles
    4. Rapid Communications
    1. Syntheses and nickel coordination properties of cyclen substituted with mixed stilbene/poly(ethylene glycol) dendritic arms (pages 5414–5428)

      Jian Weng and Qiqing Zhang

      Version of Record online: 29 SEP 2005 | DOI: 10.1002/pola.20960

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      A series of cyclens substituted with mixed stilbene and poly(ethylene glycol) dendritic arms were prepared, and their nickel coordination properties were investigated. The third-generation dendrimer terminated with CO2H could control the access of nickel and chloride ions because of the formation of an intramolecular hydrogen-bond network.

    2. Bis-dendritic polyethylene prepared by ring-opening metathesis polymerization in the presence of bis-dendritic chain transfer agents (pages 5429–5439)

      Kevin Sill and Todd Emrick

      Version of Record online: 29 SEP 2005 | DOI: 10.1002/pola.20995

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      Bis-dendritic chain transfer agents were prepared and used in the synthesis of ABA triblock copolymers by ring-opening metathesis polymerization. Subsequent hydrogenation of the center polyolefin block afforded bis-dendritic polyethylene. The properties of these unique dendritic–linear–dendritic triblock copolymer structures were studied in both solution and the bulk.

    3. Simultaneous construction of polymer backbone and side chains by three-component polycondensation. Synthesis of polyethers with propargyl side chains from dialdehydes, alkylene bis(trimethylsilyl) ethers, and allenyltrimethylsilane (pages 5440–5448)

      Lui Niimi, Shuichi Hiraoka and Tsutomu Yokozawa

      Version of Record online: 29 SEP 2005 | DOI: 10.1002/pola.21003

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      Polyethers with propargyl side chains were synthesized by the acid-catalyzed reaction of dialdehydes 1, alkylene bis(trimethylsilyl) ethers 2, and allenyltrimethylsilane 4 in one-pot.

    4. Synthesis, crystallization, and morphology of star-shaped poly(ε-caprolactone) (pages 5449–5457)

      Jing-Liang Wang, Lu Wang and Chang-Ming Dong

      Version of Record online: 29 SEP 2005 | DOI: 10.1002/pola.20954

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      Six-arm star-shaped poly(ε-caprolactone) (sPCL) with a well-defined architecture was successfully synthesized with a commercial dipentaerythritol as the initiator and stannous octoate as the catalyst in bulk at 120 °C. The polymer molecular weight was accurately predicted from the molar ratio of the monomer to the initiator. The maximal melting point, cold crystallization temperature, and degree of crystallinity of the sPCL polymers increased with increasing molecular weight, and imperfect crystallization possibly did not exist in these sPCL polymers. Moreover, both linear poly(ε-caprolactone) and sPCL with a higher molecular weight exhibited a good spherulitic morphology with apparent Maltese cross patterns.

    5. Synthesis of a new type of core–shell particle from hyperbranched polyglycerol (pages 5458–5464)

      Decheng Wan, Zhongyu Li and Junlian Huang

      Version of Record online: 30 SEP 2005 | DOI: 10.1002/pola.20949

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      A route to prepare a new type of core–shell particle with a novel topology based on hyperbranched polyglycerol (PG) was developed. The hydroxyls of PG were converted to trithiocarbonates, and the latter were used to mediate the surface graft polymerization of N,N-dimethylaminoethyl acrylate. The poly(N,N-dimethylaminoethyl acrylate) shell was crosslinked by 1,6-dibromohexane and then parted from the core by the cleavage of trithiocarbonates with sodium borohydride. Novel particles with thiol groups located on the interface between the PG core and poly(N,N-dimethylaminoethyl acrylate) shell were thus formed. The shell crosslinking could be performed at very high solid contents (2–4%). These polymer particles showed pH- and temperature-dependent solubility.

    6. Metallocene supported on a polyhedral oligomeric silsesquioxane-modified silica with high catalytic activity for ethylene polymerization (pages 5465–5476)

      Daniela Bianchini, Griselda Barrera Galland, João Henrique Z. dos Santos, Roberto J. J. Williams, Diana P. Fasce, Ignacio E. Dell'Erba, Raul Quijada and Mónica Perez

      Version of Record online: 30 SEP 2005 | DOI: 10.1002/pola.21049

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      A particular type of POSS-modified silica was synthesized and tested as a support of a metallocene used for the polymerization of olefins giving a 50% increase in the activity, compared with that of unmodified silica. Analytical data showed that two different types of catalytic sites were present in the (nBuCp)2ZrCl2/POSS/SiO2 catalyst. One type of metallocene species was directly fixed on the organic branches of POSS and a second type of catalytic sites derived from a Zr atom directly bonded to the silica surface.

    7. Poly(ionic liquid)s as new materials for CO2 absorption (pages 5477–5489)

      Jianbin Tang, Huadong Tang, Weilin Sun, Maciej Radosz and Youqing Shen

      Version of Record online: 30 SEP 2005 | DOI: 10.1002/pola.21031

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      Polymers made from ionic liquid monomers have enhanced, fast, reversible and selective CO2 sorption. The cations, anions and backbone of the polymer strongly affected the CO2 sorption capacity. The CO2 sorption of the polymers is absorption (bulk) rather than adsorption (surface). These polymers are new sorbent and membrane materials for CO2 separation. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com]

    8. Using hydrophobic additive as pore-forming agent to prepare macroporous PNIPAAm hydrogels (pages 5490–5497)

      Xian-zheng Zhang, Chih-chang Chu and Ren-xi Zhuo

      Version of Record online: 30 SEP 2005 | DOI: 10.1002/pola.21056

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      PLA nanospheres were used as an additive to investigate the influence of hydrophobic additive on properties of temperature-sensitive PNIPAAm hydrogels. Results demonstrate that the hydrophobic additive acts as the pore-forming agent like conventional used hydrophilic additive, which induces a macroporous network structure during the gelation process, and consequently improved swelling capability at room temperature and fast shrinking rate of resulting PNIPAAm hydrogels upon temperature increase.

    9. Synthesis of well-defined three-armed polystyrene having thiourethane–isocyanurate as the core structure derived from trifunctional five-membered cyclic dithiocarbonate (pages 5498–5505)

      Akane Suzuki, Daisuke Nagai, Bungo Ochiai and Takeshi Endo

      Version of Record online: 30 SEP 2005 | DOI: 10.1002/pola.20979

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      The synthesis of a three-armed polymer with an isocyanurate–thiourethane core structure is described. Trifunctional reversible addition–fragmentation chain transfer (RAFT) agent 5 was prepared from tris(mercapto-thiourethane), which was obtained from the aminolysis of trifunctional five-membered cyclic dithiocarbonate. The radical polymerization of styrene in the presence of 2,2′-azobis(isobutyronitrile) (AIBN) and trifunctional RAFT agent 5 in bulk at 60 °C proceeded to afford the corresponding three-armed polystyrene with thiourethane–isocyanurate as the core structure.

    10. Dual bimodal polyethylene prepared by intercalated silicate with nickel diimine complex (pages 5506–5511)

      Qi Wang and Peng Liu

      Version of Record online: 30 SEP 2005 | DOI: 10.1002/pola.21030

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      Polyethylenes with bimodal molecular weight distribution and bimodal branching content have been produced by one-step homopolymerization catalyzed intercalated silicate with nickel diimine complex. The effect of the laminated structure of silicate on the ethylene polymerization affects the polymerization process and produces two different chain populations, providing a new approach to tailoring the microstructure of polymer. [A color version of the adjacent figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

    11. Self-assembly of a new class of amphiphilic poly(amidoamine) dendrimers and their electrochemical properties (pages 5512–5519)

      Bing-Bing Wang, Xin Zhang, Xin-Ru Jia, Zi-Chen Li, Yan Ji and Yen Wei

      Version of Record online: 5 OCT 2005 | DOI: 10.1002/pola.21050

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      A new class of amphiphilic dendrimers consisting of a hydrophilic dendrimer core and hydrophobic aromatic shells has been synthesized. These dendrimers self-assemble into vesicular aggregates in water. The self-assembly behavior of these amphiphilic dendrimers strongly depends on their generations. The generation dependence has been further investigated by an exploration of their electrochemical properties. The photoisomerization process can cause a change in the aggregate size.

    12. Preparation of a chemically amplified photosensitive polyimide based on norbornene-end-capped poly(amic acid ethoxymethylester) (pages 5520–5528)

      Myung-Sup Jung, Sang Kyun Lee, Jinkyu Hyeon-Lee, Moon Ki Park and Hee-Tae Jung

      Version of Record online: 30 SEP 2005 | DOI: 10.1002/pola.21040

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      Scanning electron microscopy images are shown of high-resolution patterns with a film thickness of 15 μm produced from a norbornene-end-capped poly(amic acid ethoxymethylester)/diphenyliodonium 5-hydroxynaphthalene-1-sulfonate system: (a) 8-μm dots and lines/spaces, (b) 5-μm lines/spaces, (c) 20-μm holes, and (d) 10-μm holes.

    13. Effect of the initial maleic anhydride content on the grafting of maleic anhydride onto isotactic polypropylene (pages 5529–5534)

      Ronghua Zhang, Yutian Zhu, Jianguo Zhang, Wei Jiang and Jinghua Yin

      Version of Record online: 30 SEP 2005 | DOI: 10.1002/pola.21038

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      Possible structures are shown for maleic anhydride (MAH) grafted polypropylene: (1) MAH grafted to the tertiary carbons, (2) MAH grafted to the end of polypropylene chains with double bonds, (3) MAH grafted to the secondary carbons, and (4) MAH grafted to the end of iPP chains with a single bond. This study showed that the NMR signals for structures 1 and 2 increased considerably with increasing MAH content, whereas the NMR signal for structure 4 tended to decrease with increasing MAH content. This result was consistent with the previous simulation study. As for structure 3, the NMR signal was extremely low, and this indicated that the amount of this structure was quite small, as previously known.

    14. Vinylic and ring-opening metathesis polymerization of norbornene with bis(β-ketoamine) cobalt complexes (pages 5535–5544)

      Feng Bao, Xing-Qiang Lü, Haiyang Gao, Guoqiu Gui and Qing Wu

      Version of Record online: 3 OCT 2005 | DOI: 10.1002/pola.21036

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      Cobalt complexes 14 bearing N,O-chelate ligands based on condensation products of 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone with aniline, o-methylaniline, α-naphthylamine, and p-nitroaniline, respectively, were synthesized, and the structures of 1 and 4 were characterized by single-crystal X-ray diffraction analyses. The bis(β-ketoamine) cobalt complexes could act as moderately active catalyst precursors for norbornene polymerization with the activation of methylaluminoxane. This catalytic reaction proceeded mainly through a vinyl-type polymerization mechanism. 1H NMR and IR showed that in all cases, a small amount of double bonds raised from ring-opening metathesis polymerization (ROMP) was present in the polymerization products. The variation of the polymerization conditions affected the ROMP unit ratio in the polynorbornenes.

    15. Thymine-functionalized polystyrenes for applications in biotechnology. III. Increasing the thymine loading via a new synthetic pathway (pages 5545–5553)

      Michael F. Cunningham, Matthew Chatterton and Judit E. Puskas

      Version of Record online: 3 OCT 2005 | DOI: 10.1002/pola.20984

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      Thymine-containing polystyrene microspheres ∼40–70 nm in diameter were synthesized by the functionalization of poly(styrene-co-4-chloromethylstyrene) copolymers prepared with emulsion polymerization. The functionalized microspheres were characterized by elemental analysis, Fourier transform infrared, and X-ray photoelectron spectroscopy. The new synthetic approach, based on the proposed SN2 reaction mechanism shown on the right, achieved up to a 44 mol % thymine loading, which is a significant improvement over earlier reports. Analyses revealed partial hydrolysis of the chloromethylstyrene functionalities during the emulsion copolymerization step, and thus the final product had hydroxymethyl functional groups in addition to thymine and residual chloromethyl functionalities. These copolymers show promise for applications in biotechnology such as protein separation and controlled drug release.

    16. Synthesis and self-assembly of hyperbranched polymers with benzoyl terminal arms (pages 5554–5561)

      Guohua Jiang, Li Wang, Tao Chen, Xiaochen Dong, Haojie Yu, Jianfeng Wang and Chang Chen

      Version of Record online: 30 SEP 2005 | DOI: 10.1002/pola.21032

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      Hyperbranched polymers with benzoyl terminal groups (HPs-B) were synthesized through the chemical modification method. The different shapes of self-assembled structures can be formed in selected solvents. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

    17. (Co)polymerization behavior of supported metallocene catalysts. I. Ligand and substituent effect (pages 5562–5570)

      Marzena Białek, Krystyna Czaja and Aleksandra Reszka

      Version of Record online: 30 SEP 2005 | DOI: 10.1002/pola.21024

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      The metallocenes L2MCl2 (M = Zr or Ti, L = Cp, n-BuCp, i-PrCp, t-BuCp, Me5Cp, or Ind) upon immobilization on magnesium carrier were used in ethylene homopolymerization and its copolymerization with 1-hexene. The effect of catalyst composition on the anchored metal content, catalyst activity, comonomer reactivity, and polymer properties was investigated. The results obtained with supported catalysts were compared with those obtained with their homogeneous counterparts under the same (co)polymerization conditions. It was found that after immobilization the catalysts studied gave polymers with clearly higher molecular weight than did their homogeneous counterparts.

      Comparison of molecular weight of PE obtained with homogeneous and supported zirconocene catalysts: (1)-(t-BuCp)2ZrCl2; (2)-(n-BuCp)2ZrCl2; (3)-(i-PrCp)2ZrCl2; (4)-(Me5Cp)2ZrCl2; (5)-Ind2ZrCl2.

    18. Synthesis of a novel high sensitive photo-radical initiator with good thermal stability based on naphthalic-1,8-N-alkylimide derivatives (pages 5571–5580)

      Katsuya Sakayori, Yuji Shibasaki and Mitsuru Ueda

      Version of Record online: 30 SEP 2005 | DOI: 10.1002/pola.21034

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      A new high sensitive photo-radical initiato r N-[2-(2-acryloyloxyethoxy) ethyl]-1,8-naphthalimide (NI6) with good thermal stability based on naphthylimide derivative was developed. The film, consisting of NI6 and pentaerythritol triacrylate (PETA), showed high photosensitivity, and the resulting film exhibited very high transmittance over 400 nm. The thermal stability of NI6 was very high and no decomposed residues were observed from the film consisting of NI6 after heating at 250 °C for 1 h.

    19. Synthesis of dye-labeled poly(vinyl acetate-co-ethylene) (EVA) latex and polymer diffusion in their latex films (pages 5581–5596)

      Jun Wu, J. Pablo Tomba, Jung Kwon Oh, Mitchell A. Winnik, Rajeev Farwaha and Jude Rademacher

      Version of Record online: 30 SEP 2005 | DOI: 10.1002/pola.21029

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      Dye-labeled poly(vinyl acetate-co-ethylene) latexes (EVA) were synthesized and the polymer diffusion in their latex films was studied. Polymer diffusion was followed with experiments based upon fluorescence resonance energy transfer (ET). Unlike the typical polymer diffusion behavior in latex films, characterized by small extents of polymer diffusion in newly dried latex films followed with an increase of the extent of diffusion upon annealing, our ET experiments showed that polymer diffusion in these EVA latex films was complete by the time the films were dry.

    20. Ethylene/silane copolymers prepared with a metallocene catalyst as polymeric additives in polyethylene/aluminum trihydroxide composites (pages 5597–5608)

      S. Lipponen and J. Seppälä

      Version of Record online: 30 SEP 2005 | DOI: 10.1002/pola.21037

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      Metallocene-based and highly functional ethylene/silane copolymers (halo- or alcoxysilane functionalities) were used as additives in polyethylene/aluminum trihydroxide composites to promote adhesion between the filler and the matrix. The amount of functionality in the composites was kept at a low level because of the high reactivity of halo- and alcoxysilanes toward the hydroxyl groups of the inorganic filler. The toughness (notched impact strength) of the composites was increased over 100% with only 0.006 mol % chlorosilane as the functional group in the entire PE matrix.

    21. Catalytic effect of ionic liquids in the Cu2O/2,2′-bipyridine catalyzed living radical polymerization of methyl methacrylate initiated with arenesulfonyl chlorides (pages 5609–5619)

      Virgil Percec and Cristian Grigoras

      Version of Record online: 30 SEP 2005 | DOI: 10.1002/pola.21083

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      A dramatic acceleration of the living radical polymerization of methyl methacrylate initiated with arenesulfonyl chloride and catalyzed by the self-regulated Cu2O/2,2′-bipyridine in the presence of 1-butyl-3-methylimidazolium hexafluorophosphate was discovered. The rate constant of propagation of this polymerization shows an almost first order of reaction in the concentration of the ionic liquid and therefore, this ionic liquid exhibits catalytic effect.

    22. Synthesis of sulfonated poly(imidoaryl ether sulfone) membranes for polymer electrolyte membrane fuel cells (pages 5620–5631)

      Dae Sik Kim, Ho Bum Park, Jae Young Jang and Young Moo Lee

      Version of Record online: 3 OCT 2005 | DOI: 10.1002/pola.21066

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      New sulfonated poly(imidoaryl ether sulfone) copolymers derived from sulfonated 4,4′-dichlorodiphenyl sulfone, 4,4′-dichlorodiphenyl sulfone, and imidoaryl biphenol were evaluated. The proton conductivities ranged from 3.8 × 10−2 to 5 × 10−2 S/cm. The membranes maintained the original proton conductivity even after a boiling water test, and this indicated the excellent hydrolytic stability of the membranes. The methanol permeabilities ranged from 1.65 × 10−8 to 5.14 × 10−8 cm2/s. The free water in the membrane should have contributed to the methanol permeability.

    23. Synthesis of an alkali-swellable emulsion and its effect on the rate of polymer diffusion in poly(vinyl acetate-butyl acrylate) latex films (pages 5632–5642)

      Jung Kwon Oh, Liza Deleebeeck, Mitchell A. Winnik, Jude Rademacher and Rajeev Farwaha

      Version of Record online: 3 OCT 2005 | DOI: 10.1002/pola.21025

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      The influence of a weakly cross-linked poly(methacrylic acid-co-ethyl acrylate) alkali-swellable emulsions (ASE) on the rate of polymer diffusion was investigated in films formed from poly(vinyl acetate-co-butyl acryl ate) latex particles containing a small amount of acrylic acid as a comonomer. Polymer diffusion rates were monitored by the energy transfer technique. We found that the presence of the ASE component, either in the acid form or fully neutralized by ammonia or sodium hydroxide, had very little effect on the polymer diffusion rate. However, in the presence of 2 wt % NH4-ASE, there was a small but significant increase in the polymer diffusion rate.

    24. Modeling the molecular weight distribution of block copolymer formation in a reversible addition–fragmentation chain transfer mediated living radical polymerization (pages 5643–5651)

      Michael J. Monteiro

      Version of Record online: 5 OCT 2005 | DOI: 10.1002/pola.21069

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      The use of living radical polymerization has led to many new and unique block copolymer structures. Reversible addition–fragmentation chain transfer polymerization is the most versatile but is also the most mechanistically complex. To unravel the mechanism of block formation, kinetic simulations have been carried out, allowing aspects of the mechanism that are not intuitive to be understood. This article discusses the effect of the starting dormant block polymer [polymer 1–S[BOND]C(Z)[DOUBLE BOND]S] reactivity on the evolution of the molecular weight distribution.

    25. Synthesis of a thermoresponsive shell-crosslinked 3-layer onion-like polymer particle with a hyperbranched polyglycerol core (pages 5652–5660)

      Decheng Wan, Qiang Fu and Junlian Huang

      Version of Record online: 6 OCT 2005 | DOI: 10.1002/pola.21047

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      A novel thermoresponsive shell crosslinked three-layer onion-like polymer particles were prepared using hyperbranched polyglycerol (PG) as parents compound, theperiphery hydroxyl groups of PG were transformed into trithiocarbonates ([BOND]SC(S)S[BOND]) first; then, it was used as chain transfer agent to prepare star-like block copolymer of N-isopropyl acrylamide (NIPA) and N,N-dimethylaminoethyl acrylate (DMA) insequence via RAFT process. The middle layer of poly(DMA) was crosslinked with 1,8-diiodoctane and then the trithiocarbonates were reduced into thiols by sequentialtreating with sodium borohydride and formic acid; thus, the core molecule was chemically detached from the crosslinked shell and a novel shell-crosslinked polymer particle was obtained.

    26. A novel photoinimer for the polymerization of acrylates and methacrylates (pages 5661–5670)

      Bishwa R. Nayak and Lon J. Mathias

      Version of Record online: 4 OCT 2005 | DOI: 10.1002/pola.21051

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      The design and synthesis of multifunctional photoinitiaing system based on tertiary amine and benzophenone was studied, which effectively initiates the polymerization of acrylates and methacrylates. The rate of polymerization was high when the benzophenone moiety was directly attached to the parent molecule containing tertiary amine. This appears to be due to proximity effect: chemical bonding provides a high local concentration of both components of the photo-activated system involving benzophenone and a hydrogen atom source from an electron-rich tertiary amine. The high local concentration effect is more pronounced at lower concentration of photoinitiator for polymerization.

    27. Ion–dipole interaction effects in isobutylene-based ammonium bromide ionomers (pages 5671–5679)

      J. Scott Parent, Andrea Liskova, Ralph A. Whitney and R. Resendes

      Version of Record online: 4 OCT 2005 | DOI: 10.1002/pola.21028

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      Dilute solution viscosity, solid-state rheometry, and 1H-NMR linewidth analyses are used to assess the effect of ion–dipole (R′OH/NRmath imageBr) interactions on the intensity of ion-pair aggregation within a series of new isobutylene-based tetraalkylammomium bromide ionomers. While inductive/field effects on hydroxyl group polarization exert no appreciable influence on ionomer properties, sparingly-soluble, hydrogen-bonding additives are shown to relieve heightened aggregation by interacting selectively with bound ion-pairs as opposed to the bulk polymer matrix.

    28. Controlled radical polymerization of a trialkylsilyl methacrylate by reversible addition–fragmentation chain transfer polymerization (pages 5680–5689)

      M. N. Nguyen, C. Bressy and A. Margaillan

      Version of Record online: 5 OCT 2005 | DOI: 10.1002/pola.21063

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      The reversible addition–fragmentation chain transfer (RAFT) polymerization of a hydrolyzable monomer (tert-butyldimethylsilyl methacrylate) with cumyl dithiobenzoate and 2-cyanoprop-2-yl dithiobenzoate as chain-transfer agents was studied in toluene solutions at 70 °C. The profile of the number-average molecular weight versus the conversion revealed a typical trend of RAFT polymerizations with a low chain-transfer constant of the chain-transfer agent. The molecular weight started well above zero at zero conversion and converged to the theoretical straight line at full conversion. The resulting polydispersity index values around 1.10 at full conversion were indicative of a controlled growth of the polymer chains.

    29. Imidazole-initiated polymerizations of α-amino acid N-carboxyanhydrides – simultaneous chain-growth and step-growth polymerization (pages 5690–5698)

      Hans R. Kricheldorf, Colin Von Lossow and Gert Schwarz

      Version of Record online: 5 OCT 2005 | DOI: 10.1002/pola.21021

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      The imidazole-initiated polymerizations of α-amino acid NCAs combines chain-growth and step-growth polymerizations and may yield cyclic polypeptides, unless rapid precipitation of β-sheet lamellae hinders cyclization.

  3. Rapid Communications

    1. Top of page
    2. Highlights
    3. Articles
    4. Rapid Communications
    1. Transesterification of poly(ethyl-α-hydroxymethacrylate) prepared via reversible addition–fragmentation chain transfer polymerization (pages 5699–5703)

      T. Y. Joan Chiu, Martina H. Stenzel, Thomas P. Davis and Christopher Barner-Kowollik

      Version of Record online: 4 OCT 2005 | DOI: 10.1002/pola.20991

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      Living free radical polymerization was employed to prepare poly(ethyl-α-hydroxyl methacrylate) of various chain lengths, which was subsequently treated to undergo rapid intramolecular lactonization along the polymer backbone, offering access to tailored polymers of both defined chain length and degree of lactonization.

    2. Polymer surface modification using diblock copolymers containing azobenzene (pages 5704–5709)

      Tomohide Yoshida, Mototsugu Doi, Shokyoku Kanaoka and Sadahito Aoshima

      Version of Record online: 4 OCT 2005 | DOI: 10.1002/pola.21092

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      A surface-modification technique using a block copolymer of 4-[2-(vinyloxy)ethoxy]azobenzene (AzoVE) with 2-methoxyethyl vinyl ether (MOVE) is shown to permit the dynamic control of polymer surface properties such as water wettability. Poly{4-[2-(vinyloxy) ethoxy]azobenzene} is highly compatible with and diffuses readily into a range of polymers, including polyolefins, poly(ethylene terephthalate), polystyrene, and polysiloxane. In combination with an incompatible functional polymer such as poly(2-methoxyethyl vinyl ether), however, the poly{4-[2-(vinyloxy)ethoxy]azobenzene} segments act as an effective anchor for the functional polymer to fix it onto the surface of a polymer substrate.

    3. Control of the polymer molecular weight in atom transfer radical polymerization with branching/crosslinking (pages 5710–5714)

      Aileen R. Wang and Shiping Zhu

      Version of Record online: 5 OCT 2005 | DOI: 10.1002/pola.21106

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      This work demonstrated good system livingness and control over the polymer molecular weight in an atom transfer radical polymerization with branching/crosslinking. Methyl methacrylate was copolymerized with different concentration levels of a newly synthesized breakable divinyl crosslinker. The polymer samples were hydrolyzed under an acidic condition to yield soluble primary chains. The primary chains showed a linear increase in the molecular weight with the monomer conversion similar to that of methyl methacrylate homopolymers and had narrow molecular weight distributions with polydispersities lower than 1.2.

    4. Amphiphilic ruthenium benzylidene metathesis catalyst with PEG-substituted pyridine ligands (pages 5715–5721)

      Kurt Breitenkamp and Todd Emrick

      Version of Record online: 5 OCT 2005 | DOI: 10.1002/pola.21061

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      An amphiphilic ruthenium benzylidene metathesis catalyst 3 was prepared using poly(ethylene glycol) (PEG)-substituted pyridine ligands. This new catalyst is found to effectively polymerize cyclic olefins both in organic solvents and in water, demonstrating a high level of versatility and providing potential for new future studies in aqueous-based ROMP and other metathesis chemistries. [A color version of the adjacent figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

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