Journal of Polymer Science Part A: Polymer Chemistry

Cover image for Journal of Polymer Science Part A: Polymer Chemistry

15 July 2002

Volume 40, Issue 14

Pages 2215–2536

  1. Articles

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    2. Articles
    3. Rapid Communications
    4. Articles
    1. Synthesis and characterization of new poly(aryl ether)s with isolated fluorophores (pages 2215–2224)

      Shiao-Wen Hwang, Shinn-Horng Chen and Yun Chen

      Version of Record online: 5 JUN 2002 | DOI: 10.1002/pola.10341

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      Four novel poly(aryl ether)s (P1P4) consisting of alternate isolated electron-transporting and hole-transporting fluorophores were synthesized and characterized. These poly(aryl ether)s can be dissolved in organic solvents and exhibited good thermal stability. The photoluminescent spectral results of the polymers revealed that the emission of polymers was dominated by the fluorophores with longer emissive wavelength via the energy transfer from p-quaterphenyl to 3,6-bis(styryl)carbazole or 2,7-bis(styryl)fluorene segments. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital energy levels of these polymers were measured by cyclic voltammetry. The electron-donating nitrogen atom on carbazole resulted in higher HOMO energy levels of P1 and P2 but lower ΦPL than P3 and P4. The single-layer light-emitting diodes of P1, P2, and P4 revealed blue electroluminescence, but P3 emitted yellow light as a result of the excimer emission.

    2. One- and two-dimensional NMR characterization of N-vinyl-2-pyrrolidone/methyl acrylate copolymers (pages 2225–2236)

      A. S. Brar and Rajeev Kumar

      Version of Record online: 16 MAY 2002 | DOI: 10.1002/pola.10312

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      N-vinyl-2-pyrrolidone/methyl acrylate (V/M) copolymers were prepared by free-radical bulk polymerization. The copolymer composition of these copolymers was calculated from 1H NMR spectra. The radical reactivity ratios for N-vinyl-2-pyrrolidone (V) and methyl acrylate (M) were rV = 0.09, rM = 0.44. The complete spectral assignment of the 13C and 1H NMR spectra were done with distortionless enhancement by polarization transfer and two-dimensional (2D) heteronuclear single quantum correlation spectroscopic experiments. The 2D total correlation spectroscopic NMR spectrum showed the various bond interactions, thus inferring the possible structure of the copolymers.

    3. Crosslinking of vinyl-terminated biphenyl and naphthalene side-chain liquid-crystalline poly(epichlorohydrin) derivatives (pages 2237–2244)

      Lourdes Callau, Ana Mantecón and José Antonio Reina

      Version of Record online: 20 MAY 2002 | DOI: 10.1002/pola.10308

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      We performed the crosslinking of vinyl-terminated biphenyl and naphthalene side-chain liquid-crystalline polyethers using peroxide-type initiators. The crosslinking temperatures were chosen in the range of mesophase stability to allow the mesophase order to be frozen. The biphenyl derivatives were crosslinked to a large extent. This led to anisotropic thermosets. To crosslink naphthalene derivatives, amine promoters were needed, but degrees of crosslinking were lower, and anisotropic elastomers were obtained.

    4. Star-shaped polymers by Ru(II)-catalyzed living radical polymerization. II. Effective reaction conditions and characterization by multi-angle laser light scattering/size exclusion chromatography and small-angle X-ray scattering (pages 2245–2255)

      Kyung-Youl Baek, Masami Kamigaito and Mitsuo Sawamoto

      Version of Record online: 16 MAY 2002 | DOI: 10.1002/pola.10315

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      Star poly(methyl methacrylate)s (P*) of various arm lengths and core sizes were synthesized by the polymer linking reaction in Ru(II)-catalyzed living radical polymerization. The yields of the star polymers increased under the following reaction conditions: (1) at a higher concentration of living ends or arm chains ([P*]), (2) with a larger degree of polymerization of the arm chains (arm length), (3) with a larger ratio of linking agents to P* (core size), (4) at a higher temperature, (5) in a polar solvent, and (6) at a higher catalyst concentration. Multi-angle laser light scattering and small-angle X-ray scattering analyses showed that the star polymers had weight-average molecular weights of 3.8 × 103 to 1.5 × 106, 4–63 arms per molecule, radii of gyration (Rz) of 2–22 nm, and nearly spherical shapes for which the radius of the microgel core was a few nanometers.

    5. Synthesis and characterization of liquid-crystalline polyphosphonates containing disubstituted ferrocene esters as mesogens (pages 2256–2263)

      S. Senthil and P. Kannan

      Version of Record online: 16 MAY 2002 | DOI: 10.1002/pola.10257

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      A new series of liquid-crystalline polyphosphonates with 1,1′-disubstituted ferrocene in the main chain with an even number of methylene spacers (2–10) are reported. The liquid-crystalline textures were more transparent with an increase in the spacer length. The thermal properties were studied with thermogravimetric analysis and differential scanning calorimetry. The glass-transition and melting temperatures of the polymers were greatly reduced with respect to those of similar polymers without phosphorous segments. The results obtained from an energy-minimized structure with computer modeling programs provided supporting evidence for the reduction in the transition temperature and the increase in the isotropization temperature.

    6. Ring-opening polymerization of ϵ-caprolactam and ϵ-caprolactone via microwave irradiation (pages 2264–2275)

      Xiaomei Fang, Christopher D. Simone, Eleonora Vaccaro, Samuel J. Huang and Daniel A. Scola

      Version of Record online: 16 MAY 2002 | DOI: 10.1002/pola.10306

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      A novel process for synthesizing nylon-6 and poly(ϵ-caprolactone) by microwave irradiation of their respective monomers, ϵ-caprolactam and ϵ-caprolactone, is described. The ring-opening polymerization of ϵ-caprolactam was investigated with microwave irradiation in the presence of an ω-aminocaproic acid catalyst (10 mol %). The ring-opening polymerization of ϵ-caprolactone was also accomplished with microwave irradiation in the presence of a stannous octoate catalyst with and without a butanediol initiator. In both investigations, polymers were generated with properties higher than or equivalent to those of thermal processes, but in a much smaller time frame.

    7. Poly(ethylene terephthalate) copolymers containing nitroterephthalic units. III. Methanolytic degradation (pages 2276–2285)

      Darwin P. R. Kint, Antxon Martinez de Ilarduya, Jordi J. Bou and Sebastián Muñoz-Guerra

      Version of Record online: 16 MAY 2002 | DOI: 10.1002/pola.10305

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      The methanolytic degradation of random poly(ethylene terephthalate) (PET) copolymers containing 15 and 30 mol % nitroterephthalic units was investigated and compared with PET. Both copolyesters degraded faster than PET, and the degradation rate increased with the content of nitrated units and occurred preferentially by cleavage of the ester groups placed at the meta position of the nitro group in the nitrated units. A surface degradation mechanism entailing solubilization of the fragmented polymer and consequent loss of mass was found to operate in the methanolysis of the copolyesters.

    8. Controlled synthesis and chemical modification of unsaturated aliphatic (Co)polyesters based on 6,7-dihydro-2(3H)-oxepinone (pages 2286–2297)

      Xudong Lou, Christophe Detrembleur, Philippe Lecomte and Robert Jérôme

      Version of Record online: 17 MAY 2002 | DOI: 10.1002/pola.10318

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      The copolymerization of 6,7-dihydro-2(3H)-oxepinone (DHO2) with ϵ-caprolactone (ϵCL) was initiated by aluminum isopropoxide at 0 °C as an easy way to produce unsaturated aliphatic polyesters with nonconjugated C[DOUBLE BOND]C double bonds in a controlled manner. The copolymers of DHO2 and ϵCL were quantitatively oxidized with the formation of epoxides containing chains. The epoxidized copolyesters were successfully converted into thioaminated chains, which were then quaternized into polycations. No degradation occurred during the chemical modification.

    9. Benzyl alcohols as accelerators in the photoinitiated cationic polymerization of epoxide monomers (pages 2298–2309)

      James V. Crivello and Ricardo Acosta Ortiz

      Version of Record online: 17 MAY 2002 | DOI: 10.1002/pola.10311

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      Benzyl alcohols display marked accelerating effects on the onium salt photoinitiated cationic ring-opening polymerizations of epoxide monomers. These results have been explained as a result of rapid chain transfer from the interaction of the hydroxyl group of benzyl alcohol with the growing chain end. In addition, it is proposed that the benzyl ether generated participates in the radical chain-induced decomposition of the onium salt photoinitiator.

    10. Reactivity of common functional groups with urethanes: Models for reactive compatibilization of thermoplastic polyurethane blends (pages 2310–2328)

      Qi-Wei Lu, Thomas R. Hoye and Christopher W. Macosko

      Version of Record online: 22 MAY 2002 | DOI: 10.1002/pola.10310

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      Two model urethane compounds, dibutyl 4,4′-methylenebis(phenyl carbamate) and dioctyl 4,4′-methylenebis(phenyl carbamate) (OMO) were prepared. The reactions of the two model urethane compounds with several small monofunctional compounds were carried out with neat mixtures at elevated temperatures. The ranking of reactivity of the functional groups with the urethanes was determined as follows—primary amine > secondary amine ≫ hydroxyl ∼ acid ∼ anhydride ≫ epoxide. Conversions of carbamate in each reaction were monitored over time at 200 °C. The reactions between OMO and primary amine were conducted at 170, 180, 190, and 200 °C and best described by a second-order bimolecular reaction model. The rate constant was estimated to be 1.8 × 10−3 L · mol−1 · s−1 and activation energy 115 kJ · mol−1.

    11. Flame-retardant epoxy resins from o-cresol novolac epoxy cured with a phosphorus-containing aralkyl novolac (pages 2329–2339)

      Ying Ling Liu, Chuan Shao Wu, Keh Ying Hsu and Teh Chou Chang

      Version of Record online: 23 MAY 2002 | DOI: 10.1002/pola.10320

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      A novel phosphorus-containing aralkyl novolac (Ar-DOPO-N) was prepared from the reaction of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) first with terephthaldicarboxaldehyde (TDCA) and subsequently with phenol. Ar-DOPO-N blended with phenol formaldehyde novolac and melamine-modified novolac was used as a curing agent for o-cresol formaldehyde novolac epoxy, resulting in cured epoxy resins with high glass-transition temperatures, good thermal stability, and good flame retardance.

    12. Synthesis and characterization of water-soluble hyperbranched poly(ester amine)s from diacrylates and diamines (pages 2340–2349)

      Chao Gao, Wei Tang and Deyue Yan

      Version of Record online: 24 MAY 2002 | DOI: 10.1002/pola.10322

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      Various water-soluble hyperbranched poly(ester amine)s were synthesized by the direct polyaddition of diamines to diacrylates in the absence of a catalyst. Each diamine contained a secondary amino group and a primary amino group such as 1-(2-aminoethyl)piperazine, N-methyl-1,3-propanediamine, or N-ethylethylenediamine. Fourier transform infrared and mass spectrometry were used to investigate the reaction procedure. The secondary amino group of diamine reacted faster with the vinyl group of diacrylate; this resulted in the formation of the intermediate with an acrylate group and two active hydrogen atoms attached to a nitrogen atom. Further self-polyaddition of the intermediate, a kind of AB2-type monomer, gave the hyperbranched poly(ester amine).

    13. End-group modification of poly(butyl acrylate) prepared by atom transfer radical polymerization: Mechanistic study using gradient polymer elution chromatography (pages 2350–2359)

      Auke Snijder, Bert Klumperman and Rob Van Der Linde

      Version of Record online: 30 MAY 2002 | DOI: 10.1002/pola.10321

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      The introduction of a functional group into a poly(butyl acrylate) polymer prepared with copper-mediated atom transfer radical polymerization is reported. The bromo end group of the initial polymer can be transformed into a different functional group with several functionalization reactions, including nucleophilic substitution and atom transfer radical addition, in combination with comonomers, addition–fragmentation transfer agents, or stable radicals. Several new functionalization agents are reported. The rate constant of the functionalization reaction and the final functionality are determined with gradient polymer elution chromatography, a technique by which qualitative and quantitative information about the conversion can be obtained. Polymers with a functionality greater than 95% are reported.

    14. Synthesis, optical, and electrochemical properties of novel copolymers on the basis of benzothiadiazole and electron-rich arene units (pages 2360–2372)

      M. Jayakannan, Paul A. Van Hal and René A. J. Janssen

      Version of Record online: 30 MAY 2002 | DOI: 10.1002/pola.10327

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      Six novel alternating conjugated copolymers consisting of an electron-deficient benzothiadiazole and a variety of electron-rich thiophene-arene-thiophene units were synthesized by palladium-catalyzed polycondensations (Stille and Suzuki reactions), aiming at processable materials with a reduced optical band gap. The optical and electrochemical properties of the polymers were examined in detail and analyzed in relation to the molecular structure.

    15. Cure kinetics of the ring-opening metathesis polymerization of dicyclopentadiene (pages 2373–2383)

      M. R. Kessler and S. R. White

      Version of Record online: 30 MAY 2002 | DOI: 10.1002/pola.10317

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      The cure kinetics of polydicyclopentadiene prepared by ring-opening metathesis polymerization with three different concentrations of Grubbs' catalyst were examined with differential scanning calorimetry. The experimental data were used to test several different phenomenological kinetic models. The data were best modeled with a model-free isoconversional method. This analysis revealed that the activation energy increased significantly for degrees of cure greater than 60%. The catalystconcentration had a large effect on the cure kinetics.

    16. Biologically active polymers. V. Synthesis and antimicrobial activity of modified poly(glycidyl methacrylate-co-2-hydroxyethyl methacrylate) derivatives with quaternary ammonium and phosphonium salts (pages 2384–2393)

      El-Refaie Kenawy, Fouad I. Abdel-Hay, Abd El-Raheem R. El-Shanshoury and Mohamed H. El-Newehy

      Version of Record online: 30 MAY 2002 | DOI: 10.1002/pola.10325

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      Antimicrobial copolymers bearing quaternary ammonium and phosphonium salts based on a copolymer of glycidyl methacrylate and 2-hydroxyethyl methacrylate were synthesized. Poly(glycidyl methacrylate-co-2-hydroxyethyl methacrylate) was modified for the introduction of chloromethyl. The chloroacetylated copolymer was modified for the production of quaternary ammonium or phosphonium salts. The antimicrobial activity of the obtained copolymers was studied against gram-negative bacteria (Escherichiacoli, Pseudomonas aeruginosa, Shigella sp., and Salmonella typhae), gram-positive bacteria (Bacillus subtilus and B. cereus), and the fungus Trichophyton rubrum. The results showed that the three copolymers had high antimicrobial activity, and the copolymer bearing quaternary salt made from tributyl phosphine was the most effective copolymer against both gram-negative and gram-positive bacteria and the fungus T. rubrum.

    17. Synthesis of comb-branched polyacrylamide with cationic poly[(2-dimethylamino)ethyl methacrylate dimethylsulfate] quat (pages 2394–2405)

      Faquan Zeng, Youqing Shen and Shiping Zhu

      Version of Record online: 30 MAY 2002 | DOI: 10.1002/pola.10323

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      Comb-branched polyelectrolytes were synthesized by the free- radical copolymerization of acrylamide with the poly[(2-dimethylamino)ethyl methacrylate methylsulfate] macromonomer. The macromonomer, bearing a chain-end styrenic moiety, was prepared by a living anionic polymerization method. The macromonomer had a much higher reactivity than acrylamide in the copolymerization. A semibatch feeding process was developed to give a uniform composition for the copolymer products.

    18. Synthesis and characterization of polystyrene-b-poly (1,2-isoprene-ran-3,4-isoprene) block copolymers with azobenzene side groups (pages 2406–2414)

      Teruaki Hayakawa, Shin Horiuchi, Hiroshi Shimizu, Tadashi Kawazoe and Motoichi Ohtsu

      Version of Record online: 30 MAY 2002 | DOI: 10.1002/pola.10330

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      Polystyrene-b-poly(1,2-isoprene-ran-3,4-isoprene) block copolymers with azobenzene side groups were synthesized. The microstructure of these block copolymer films was investigated using both transmission electron microscopy and near-field optical microscopy.

    19. Chain-transfer reaction in the radical polymerization of di-n-butyl itaconate at high temperatures (pages 2415–2426)

      Tomohiro Hirano, Ryoko Takeyoshi, Makiko Seno and Tsuneyuki Sato

      Version of Record online: 30 MAY 2002 | DOI: 10.1002/pola.10316

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      The structures of poly(di-n-butyl itaconate)s [poly(DBI)s] prepared by radical polymerizations were studied with 13C NMR spectroscopy. Intramolecular chain-transfer reactions took place at temperatures higher than 60 °C and accompanied a decrease in the syndiotacticity of the obtained poly(DBI)s. This suggested a dependence of the intramolecular chain-transfer reactions on the stereochemistry near the propagating chain end.

    20. Preparation of amphiphilic statistical copolymers of 2-hydroxyethyl methacrylate with 2-diethylaminoethyl methacrylate, precursors of water-soluble copolymers (pages 2427–2434)

      Gerardo Martinez, Manuel Sanchez-Chaves and Enrique Lopez Madruga

      Version of Record online: 3 JUN 2002 | DOI: 10.1002/pola.10329

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      Monomer reactivity ratios of statistical copolymers of 2-hydroxyethyl methacrylate (HEMA) and 2-diethtylaminoethyl methacrylate (DEA) were determined and revealed a noticeable solvent effect. The quaternization of DEA residues led to water-soluble copolymers when the HEMA content was lower than 0.25.

    21. Kinetics of the polycondensation and copolycondensation of bis(3-hydroxypropyl) terephthalate and bis(4-hydroxybutyl) terephthalate (pages 2435–2441)

      Joon Ho Kim, Jun Ho Park, Chang Hwan Kwon and Won Seok Lyoo

      Version of Record online: 3 JUN 2002 | DOI: 10.1002/pola.10347

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      The kinetics of the polycondensation and copolycondensation reactions of bis(3-hydroxypropyl) terephthalate (BHPT) and bis(4-hydroxybutyl) terephthalate (BHBT) as monomers were investigated at 270 °C in the presence of a catalyst. The rate constants of the polycondensation and cross reactions in the copolycondensation of BHPT and BHBT were determined.

    22. Bivariate distribution in copolymers: A new model (pages 2442–2448)

      Maurizio S. Montaudo, Grażyna Adamus and Marek Kowalczuk

      Version of Record online: 3 JUN 2002 | DOI: 10.1002/pola.10328

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      A new model for the bivariate distribution of chain sizes and composition in copolymers is presented. The molar fraction of chains AmBn in this model is given by a new formula that consists of the sum of two components. The predictions of the model were compared with mass spectrometric data relative to a block copolymer sample containing structural units of pivalolactone and 3-hydroxybutyrate with some literature data, namely, mass spectrometric data concerning a random copolymer sample prepared at high conversion and containing units of styrene and methyl methacrylate as well as a block copolymer sample containing units of α-methyl styrene and methyl methacrylate.

    23. Cationic copolymerization of indene with styrene derivatives: Synthesis of random copolymers of indene with high molecular weight (pages 2449–2457)

      Shokyoku Kanaoka, Nobuyuki Ikeda, Akira Tanaka, Hitoshi Yamaoka and Toshinobu Higashimura

      Version of Record online: 5 JUN 2002 | DOI: 10.1002/pola.10340

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      Random copolymers with high molecular weights (number-average molecular weight: 8–9 × 104) that consist of almost equimolar indene and p-methylstyrene (pMeSt) units were synthesized by cationic polymerization with trichloroacetic acid/tin tetrachloride in CH2Cl2 at low temperatures. This is indeed quite unexpected behavior for the combination of these two monomers because pMeSt was polymerized over 1000 times faster than indene in the homopolymerization. NMR analysis and thermal-property data showed that the copolymers obtained from indene and pMeSt were random in monomer sequence.

    24. Synthesis and properties of polyacetylenes with salicylideneaniline groups (pages 2458–2463)

      S. M. Abdul Karim, Ryoji Nomura and Toshio Masuda

      Version of Record online: 3 JUN 2002 | DOI: 10.1002/pola.10334

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      Polyacetylenes with salicylideneaniline groups were synthesized in excellent yields with a rhodium catalyst. The formed polymers exhibited largely Stokes-shifted fluorescence (emission wavelength ≃ 550 nm) upon photoexcitation at 350, which was absent in poly(phenylacetylene).

    25. Synthesis of a new amino acid/sulfur dioxide copolymer and its use in aqueous two-phase polymer systems (pages 2464–2477)

      Sk. Asrof Ali, Hasan A. Al-Muallem and Mohamed I. M. Wazeer

      Version of Record online: 5 JUN 2002 | DOI: 10.1002/pola.10336

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      A diallylamine salt underwent copolymerization with sulfur dioxide and afforded a cationic polyelectrolyte that, upon hydrolysis of the pendent ester groups, led to an anionic polyelectrolyte, a cationic acid salt, and a polybetaine. The solution properties and aqueous two-phase systems of the polyelectrolyte and poly(ethylene glycol) were studied in detail.

    26. Synthesis of nonlinear optical polyimides containing azodiamine derivative chromophores and their electrooptic and thermal properties (pages 2478–2486)

      Yuming Zhou, Weinan Leng, Xiaojuan Liu, Qunhua Xu, Jikang Feng and Juzheng Liu

      Version of Record online: 3 JUN 2002 | DOI: 10.1002/pola.10345

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      Four polyimides were prepared by the ring-opening polyaddition of 4,4′-(hexafluoroisopropylidene) diphthalic anhydride and pyromellitic dianhydride with two aromatic azodiamine derivatives as the nonlinear optical chromophores. On the basis of ZERNER'S INDO methods, according to the sum-over-states formula, a program for the calculation of nonlinear second-order optical susceptibilities was devised for the calculation of the β values of the two chromophores. The optimal temperatures for corona poling were obtained. These materials exhibited relatively large γ33 values (21 pm/V at 830 nm).

    27. Pd(0)-catalyzed polyaddition of bifunctional vinyloxiranes with 1,3-dicarbonyl compounds: The synthesis of polymers containing hydroxy and carbonyl groups (pages 2487–2494)

      Toshio Koizumi, Jun Sakamoto, Yasuhiko Gondo and Takeshi Endo

      Version of Record online: 3 JUN 2002 | DOI: 10.1002/pola.10346

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      The Pd(0)-catalyzed polyaddition of bifunctional vinyloxiranes (1a and 1b) with 1,3-dicarbonyl compounds proceeded successfully and gave polymers with an allyl alcohol moiety in the main chain and ketone and ester groups in the side groups.

  2. Rapid Communications

    1. Top of page
    2. Articles
    3. Rapid Communications
    4. Articles
    1. You have free access to this content
      Correction of an old chemical error (page 2495)

      Peter H. Plesch

      Version of Record online: 4 JUN 2002 | DOI: 10.1002/pola.10313

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      In the cationic polymerization of styrene (M; [M] = m) initiated with HClO4 (E; [E] = a0), at constant a0, the minimum value of m/a0 at which the polystyryl perchlorate ester (EMn) ionizes depends on both n and K. The previous conclusion derived 40 years ago, that for constant a0, n = 4, is false.

    2. You have free access to this content
      Isotactic-specific radical polymerization of methacrylamides in the presence of Lewis acids (pages 2496–2500)

      Yoshikatsu Suito, Yutaka Isobe, Shigeki Habaue and Yoshio Okamoto

      Version of Record online: 4 JUN 2002 | DOI: 10.1002/pola.10337

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      The radical polymerization of N-methylmethacrylamide (MMAM) and N-isopropylmethacrylamide (IPMAM) was carried out in the presence of various Lewis acids. The isotacticity (mm) of the polymers obtained from the polymerization of MMAM and IPMAM in the presence of Yb(OTf)3 reached 59 and 67%, respectively, although the radical polymerization in the absence of Lewis acids gave syndiotactic polymers. The phase-transition temperature of poly(N-isopropyl- methacrylamide) depended on the tacticity.

  3. Articles

    1. Top of page
    2. Articles
    3. Rapid Communications
    4. Articles
    1. Preparation of novel, high-modulus, swollen- or jungle-gym-type polyimide gels end-crosslinked with 1,3,5-tris(4-aminophenyl)benzene (pages 2501–2512)

      Jionghao He, Shinjiro Machida, Hiromitsu Kishi, Kazuyuki Horie, Hidemitsu Furukawa and Rikio Yokota

      Version of Record online: 4 JUN 2002 | DOI: 10.1002/pola.10335

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      A novel preparation approach for high-performance polyimide gels that are swollen or have a jungle-gym-type structure is proposed. Three different kinds of amic acid oligomers derived from pyromellitic dianhydride (PMDA), 4,4′-oxydiphthalic anhydride (ODPA), p-phenylenediamine (PDA), and 4,4′-oxydianiline (ODA) were end-crosslinked with 1,3,5-tris(4-aminophenyl)benzene (TAPB) at a high temperature. Transparent polyimide gels were obtained from the ODPA–ODA/TAPB series with high compression moduli of about 1 MPa at their equilibrium swollen states. Jungle-gym-type polyimide gels with a density of 0.5 g cm−1 were obtained after drying for the PMDA–PDA/TAPB and PMDA–ODA/TAPB series.

    2. Controlled-release systems based on the intercalation of polymeric metribuzin onto montmorillonite (pages 2513–2525)

      Ahmed Rehab, Ahmed Akelah and Maisa M. El-Gamal

      Version of Record online: 4 JUN 2002 | DOI: 10.1002/pola.10326

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      Polymer–clay composites containing metribuzin were prepared. This was achieved by preparation of monomeric metribuzin followed by solution free radical polymerization with different comonomers. The intercalation of the prepared co- and terpolymers onto montmorillonite clay were carried out through ion-exchange process. The characterization and release studies of the products, in addition to the pots and field application, have been investigated.

    3. Use of blowing catalysts for integral skin polyurethane applications in a controlled molecular architectural environment: Synthesis and impact on ultimate physical properties (pages 2526–2536)

      Tarek M. Madkour and Rasha A. Azzam

      Version of Record online: 4 JUN 2002 | DOI: 10.1002/pola.10344

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      Polyurethane elastomers of a controlled molecular architecture were synthesized using a two-step polymerization technique. Two-dimensional bifurcated hydrogen-bonding networks incorporating the urea groups were, with differential scanning calorimetric and dynamic mechanical thermal analyzer techniques, responsible for the sharp interface morphology between the pure “hard” domains and pure “soft” domains. The higher extent of the phase separation between the two phases contributed to higher elastic moduli for the hard blocks and higher tensile strength for the elastomeric samples. Higher elongation values were attributed to the liberation of the elastomeric chain ends that otherwise would have been constrained in the interface region.

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