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61.
Masato Doura Hiroyuki Aota Akira Matsumoto 《Journal of polymer science. Part A, Polymer chemistry》2004,42(9):2192-2201
Novel amphiphilic network polymers consisting of nonpolar, short primary polymer chains and polar, long crosslink units were prepared, and the swelling behavior of resulting amphiphilic gels is discussed by focusing on the influence of characteristic dangling chains; that is, benzyl methacrylate (BzMA) was copolymerized with tricosaethylene glycol dimethacrylate [CH2?C(CH3)CO(OCH2CH2)23OCOC(CH3)?CH2, PEGDMA‐23] in the presence of lauryl mercaptan as a chain‐transfer agent because BzMA forms nonpolar, short primary polymer chains and PEGDMA‐23 as a crosslinker contains a polar, long poly(oxyethylene) unit. The enhanced incorporation of dangling chains into the network polymer was brought by shortening the primary polymer chain length, and copolymerization with methoxytricosaethylene glycol methacrylate, a mono‐ene counterpart of PEGDMA‐23, enforced the incorporation of flexible dangling poly(oxyethylene) chains into the network polymer, although the former dangling chains as terminal parts of primary poly(BzMA) chains were rather rigid. Then, the influence of characteristic dangling chains on the swelling behavior of amphiphilic gels was examined in mixed solvents consisting of nonpolar t‐butylbenzene and polar methanol. The profiles of the solvent‐component dependencies of the swelling ratios were characteristic of amphiphilic gels. The introduction of dangling poly(oxyethylene) chains led not only to an increased swelling ratio but also to sharpened swelling behavior of amphiphilic gels. The swelling response of amphiphilic gels was checked by changing the external solvent polarity. The dangling chains with freely mobile end segments influenced the swelling response of gels. The amphiphilic gels with less entangled, collapsed crosslink units exhibited faster swelling response than the ones with more entangled, collapsed primary polymer chains. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2192–2201, 2004 相似文献
62.
Kenneth Ekman Lars Ekholm Jan H. Nsman 《Journal of polymer science. Part A, Polymer chemistry》1995,33(16):2699-2703
The radiation induced graft copolymerization of m-isopropenyl-α,α-dimethyl benzyl iso-cyanate (m-TMI) and styrene onto polypropylene was carried out. The extent of grafting increased with increasing amount of styrene and with increased radiation dose. A graft load of 180% was obtained by immersing a 50 kGy pre-irradiated film in a monomer solution containing 25 mol % m-TMI and 75 mol % styrene. The graft copolymer is suitable for covalently binding nonpolymerizable stabilizers with a suitable nucleophilic moiety. In this work the isocyanate moiety of the graft copolymer was allowed to react with 4-amino-2,2,6,6-tetramethyl piperidine, a hindered amine light stabilizer. Fourier trans-formed infrared spectroscopy confirmed the formation of an urea moiety. © 1995 John Wiley & Sons, Inc. 相似文献
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64.
Biju PhilipK. Sreekumar 《European Polymer Journal》2002,38(12):2441-2447
A polyamic acid containing 2,2′-dinitrodiphenylmethane segments in the main chain was synthesized from 4,4′-diamino-2,2′-dinitrodiphenylmethane and pyrromellitic dianhydride. Irradiation of the polyamic acid was done in solution (in a protic solvent, isopropanol, in isopropanol in the presence of a triplet exciter, benzophenone and in acidified isopropanol) and as thin film. The irradiations were done in an immersion type photoreactor using a 125 W high-pressure mercury vapour lamp. The average molecular weights of the polymers were determined by gel permeation chromatography. The polydispersity index of the polyamic acid and the photoproduct showed the absence of photodegradation. The photoproducts were identified by comparing the spectra of polymer photoproducts with that of low molecular weight 2,2′-dinitrodiphenylmethane derivatives under identical conditions. A possible mechanism for the phototransformations is suggested. Evaluation of photoresist behaviour of the polyamic acid was also done. 相似文献
65.
Synthesis of stereoisomers of 6′‐mono‐ and 4′,6′‐di‐O‐benzyl cryptofolione is described through a key intermediate 6 , which was prepared by coupling of iodobenzene 8 with chiral propargyl alcohol 9 under Cosford protocol conditions. Monobenzyl ether 4 is obtained via epoxide 6 opening with vinyl Grignard, followed by cross‐metathesis reaction with a vinyl lactone 11 . Whereas, dibenzyl ether 5 is prepared by epoxide 6 opening with chiral propargyl alcohol 7 followed by simple transformations and finally cis‐Wittig olefination. 相似文献
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67.
Dieter Seebach W. Bernd Schweizer Stefan Grimme Christian Mück‐Lichtenfeld 《Helvetica chimica acta》2010,93(1):1-16
The PF6 salts of 5‐benzyl‐1‐isopropylidene‐ and 5‐benzyl‐1‐cinnamylidene‐3‐methylimidazolidin‐4‐ones 1 (Scheme) with various substituents in the 2‐position have been prepared, and single crystals suitable for X‐ray structure determination have been obtained of 14 such compounds, i.e., 2 – 10 and 12 – 16 (Figs. 2–5). In nine of the structures, the Ph ring of the benzyl group resides above the heterocycle, in contact with the cis‐substituent at C(2) (staggered conformation A ; Figs. 1–3); in three structures, the Ph ring lies above the iminium π‐plane (staggered conformation B ; Figs. 1 and 4); in two structures, the benzylic C? C bond has an eclipsing conformation ( C ; Figs. 1 and 5) which places the Ph ring simultaneously at a maximum distance with its neighbors, the CO group, the N?C‐π‐system, and the cis‐substituent at C(2) of the heterocycle. It is suggested by a qualitative conformational analysis (Fig. 6) that the three staggered conformations of the benzylic C? C bond are all subject to unfavorable steric interactions, so that the eclipsing conformation may be a kind of ‘escape’. State‐of‐the‐art quantum‐chemical methods, with large AO basic sets (near the limit) for the single‐point calculations, were used to compute the structures of seven of the 14 iminium ions, i.e., 3, 4 / 12, 5 – 7, 13 , and 16 (Table) in the two staggered conformations, A and B , with the benzylic Ph group above the ring and above the iminium π‐system, respectively. In all cases, the more stable computed conformer (‘isolated‐molecule’ structure) corresponds to the one present in the crystal (overlay in Fig. 7). The energy differences are small (≤2 kcal/mol) which, together with the result of a potential‐curve calculation for the rotation around the benzylic C? C bond of one of the structures, 16 (Fig. 8), suggests that the benzyl group is more or less freely rotating at ambident temperatures. The importance of intramolecular London dispersion (benzene ring in ‘contact’ with the cis‐substituent in conformation A ) for DFT and other quantum‐chemical computations is demonstrated; the benzyl‐imidazolidinones 1 appear to be ideal systems for detecting dispersion contributions between a benzene ring and alkyl or aryl CH groups. Enylidene ions of the type studied herein are the reactive intermediates of enantioselective organocatalytic conjugate additions, Diels–Alder reactions, and many other transformations involving α,β‐unsaturated carbonyl compounds. Our experimental and theoretical results are discussed in view of the performance of 5‐benzyl‐imidazolidinones as enantioselective catalysts. 相似文献
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70.
研究了 PMO-SBA-15 材料负载的金属钯纳米粒子 (Pd/PMO-SBA-15) 在水相中催化苯甲醇选择氧化制苯甲醛的反应. 考察了纳米粒子种类、氧化剂用量、反应时间和反应温度等对苯甲醇转化率及苯甲醛选择性的影响. 结果表明, 以水为溶剂, 以 H2O2 (30%) 为氧化剂时, 可得到较高的苯甲醇转化率和苯甲醛选择性. 当以 0.05 g 的 2%Pd/PMO-SBA-15 为催化剂, H2O2 用量为 1.5 ml, 反应温度为 80 oC, 反应 4 h 时, 苯甲醇转化率和苯甲醛选择性分别达到 97.1% 和 100.0%. 对该催化体系的重复使用性能进行了考察. 结果发现, 随着使用次数的增加, 苯甲醇转化率有所下降, 但苯甲醛选择性保持不变. 相似文献