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三元共聚物聚甲基乙撑-环己撑碳酸酯的合成与表征 总被引:1,自引:0,他引:1
报道了三元共聚物聚甲基乙撑-环己撑碳酸酯的制备与性能研究. 实验采用高活性的负载戊二酸锌作为催化剂, 在不添加任何溶剂的情况下, 以二氧化碳和环氧丙烷、环氧环己烷为原料, 制备了不同环己撑碳酸酯含量的三元共聚物, 并对其结构和热性能、力学性能进行了表征和分析. 结果表明这些三元共聚物具有较高的分子量, 且玻璃化转变温度随着主链上的环己撑碳酸酯含量增加而逐渐升高. 同时三元共聚物表现出比二元共聚物更好的力学性能. 相似文献
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可生物降解多嵌段聚(酯-氨酯)的合成及其热致形状记忆性质 总被引:2,自引:0,他引:2
以端羟基L-丙交酯/乙交酯共聚物(PLLG-diol)和端羟基ε-己内酯/乙交酯共聚物(PCG-diol)为硬段和软段,通过与二异氰酸酯反应制得了软、硬分子量和组成均可调的多嵌段聚(酯-氨酯),表征了它们的形状记忆行为.多嵌段聚(酯-氨酯)具有良好的形状记忆性质,应变固定率达98%~99.5%,应变恢复率达93%~98.5%;通过转变温度的调节,可使多嵌段聚(酯-氨酯)在37℃体温下不发生形状变化,而在稍高于体温的温度(40~50℃)下恢复原始形状,其形状恢复速率可通过温度和升温速率来调节. 相似文献
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生物可降解磷酸酯-碳酸酯共聚物的合成及性能研究 总被引:3,自引:0,他引:3
通过光气,二氯磷酸酯和双酚A反应,合成六种磷酸酯 碳酸酯共聚物,用IR、1H NMR及元素分析表征了共聚物,测量了Mn和热学性质.初步研究了在pH74磷酸盐缓冲溶液中,核糖核酸酶或碱性磷酸酶存在下的体外降解性能及其对抗肿瘤药物5 Fu的释放性能. 相似文献
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High-activity,single-site catalysts for the alternating copolymerization of CO2 and propylene oxide 总被引:2,自引:0,他引:2
Allen SD Moore DR Lobkovsky EB Coates GW 《Journal of the American Chemical Society》2002,124(48):14284-14285
Despite recent advances regarding catalysts for CO2/epoxide copolymerization, the development of high-activity catalysts for alternating polymerization of CO2 and commodity epoxides, such as propylene oxide, remains a challenge. A new class of unsymmetrically substituted beta-diiminate zinc complexes is reported that exhibits unprecedented activity for CO2/propylene oxide copolymerization. The polymers formed are of high molecular weight (Mn approximately 35 kg/mol) and have narrow polydispersities (PDI approximately 1.1), consistent with a living polymerization. 相似文献
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New tetravalent metal complexes with a trianionic [ONNO]-tetradentate ligand and an ancillary chloride ligand were synthesized as catalysts for the copolymerization of epoxides with carbon dioxide (CO(2)). All of the titanium, zirconium, germanium, and tin complexes were found to copolymerize epoxides with CO(2). In particular, the copolymerization of propylene oxide with CO(2) gave the almost-completely alternating copolymers by using titanium or germanium complexes. These results are the first example of the copolymerization using tetravalent metal complexes as a main component of catalysts. 相似文献
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Wu GP Wei SH Ren WM Lu XB Xu TQ Darensbourg DJ 《Journal of the American Chemical Society》2011,133(38):15191-15199
Selective transformations of carbon dioxide and epoxides into biodegradable polycarbonates by the alternating copolymerization of the two monomers represent some of the most well-studied and innovative technologies for potential large-scale utilization of carbon dioxide in chemical synthesis. For the most part, previous studies of these processes have focused on the use of aliphatic terminal epoxides or cyclohexene oxide derivatives, with only rare reports concerning the synthesis of CO(2) copolymers from epoxides containing electron-withdrawing groups such as styrene oxide. Herein we report the production of the CO(2) copolymer with more than 99% carbonate linkages from the coupling of CO(2) with epichlorohydrin, employing binary and bifunctional (salen)cobalt(III)-based catalyst systems. Comparative kinetic studies were performed via in situ infrared measurements as a function of temperature to assess the activation barriers for the production of cyclic carbonate versus copolymer involving two electronically different epoxides: epichlorohydrin and propylene oxide. The relative small activation energy difference between copolymer versus cyclic carbonate formation for the epichlorohydrin/CO(2) process (45.4 kJ/mol) accounts in part for the selective synthesis of copolymer to be more difficult in comparison with the propylene oxide/CO(2) case (53.5 kJ/mol). Direct observation of the propagating polymer-chain species from the binary (salen)CoX/MTBD (X = 2,4-dinitrophenoxide and MTBD = 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene) catalyst system by means of electrospray ionization mass spectrometry confirmed the perfectly alternating nature of the copolymerization process. This observation in combination with control experiments suggests possible intermediates involving MTBD in the CO(2)/epichlorohydrin copolymerization process. 相似文献
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由环氧丙烷(PO)和CO2交替共聚合成脂肪族聚碳酸亚丙酯,CO2利用率高, 所得产物具有一定的力学性能和生物降解性能, 具有广泛应用前景. 目前, 用于CO2和环氧化合物共聚的催化体系主要包含锌、钴、镉、铬、铝和稀土等金属活性中心, 结构、活性各异的催化剂体系, 其催化性能和产物性能也各具特色. 其中, 稀土三元催化剂(ZnEt2-甘油-三氯乙酸钇)因合成聚碳酸酯产物的分子量高、碳酸酯单元含量高、聚醚及环碳酸酯副产物少的特点而受到关注. 但是由于催化剂催化效率低, 聚合时间长, 产品成本高, 使得工业化规模生产受到限制.本文基于稀土三元催化体系, 将催化剂负载于硅胶及锌改性硅胶, 优化了其制备条件, 同时考察了添加季铵盐对催化CO2/环氧丙烷共聚合成聚碳酸酯性能的影响. 结果表明, 在1 L聚合釜中, 于3.5 MPa和70 oC反应条件下, ZnO担载量及ZnO/SiO2添加量对反应性能均有影响. 当3 wt% ZnO/SiO2的添加量为5 g时, 稀土三元催化体系的活性为4845.2 g/molZn..所得聚合物经过多次纯化处理后, 能够有效提高材料的热学性能, 即有效除去产物中的ZnO对聚合物的热稳定性有重要作用. 添加含有不同阴离子(F- , Cl- 和Br- )的季铵盐可显著影响稀土三元催化剂的活性. 其中, 仅四甲基氟化铵可以明显提高反应活性乃至聚合物分子量. 在3 wt% ZnO/SiO2载体和四甲基氟化铵的协同作用下, 稀土三元催化体系的共聚性能明显提 升, 活性最高可达5223.0 g/molZn. 聚合物结构分析表明, 在载体和四甲基氟化铵存在下, 聚合物分子量明显提高, 可达到20万以上, 分子量分布明显变窄, 且聚合物结构如碳酸酯的单元含量、副产物含量以及聚合物产品玻璃化温度基本不变, 后者均保持在40-41 ?C. 基于此, 我们提出了在ZnO改性硅胶载体及四甲基氟化铵存在下稀土三元催化体系催化CO2/环氧丙烷共聚的反应机理: ZnO/SiO2载体有利于稀土三元催化体系的分散, 而四甲基氟化铵则有利于吸附在ZnEt2上的环氧丙烷开环. 相似文献
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Aluminum porphyrin complexes are heavy-metal-free and soil-tolerant green catalysts for the copolymerization of CO2 and propylene oxide (PO),but they suffer from relatively poor poly(propylene carbonate) (PPC) selectivity.Herein,steric hindrance porphyrin ligand was used to enhance the PPC selectivity.Typically,a bulky anthracene-like group was incorporated into the porphyrin ring to form 5,10,15,20-tetra(1,2,3,4,5,6,7,8-octahydro-1,4:5,8-dimethanoanthracen-9-yl)porphyrin,the aluminum porphyrin complex with this ligand,in combination with bis(triphenylphosphine)iminium chloride as a co-catalyst,produced completely alternate PPC.Additionally,the obtained PPC showed high regioselectivity,with a head-to-tail linkage content (HT) of 92%.Therefore,we demonstrated that introduction of bulky steric ligand into the porphyrin ring could reduce the propylene oxide homopolymerization activity leading to excellent PPC selectivity,and improve regioselectivity for the PO ring-opening during the copolymerization. 相似文献
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Daisuke Takeuchi Yoshihiko Sakaguchi Kohtaro Osakada 《Journal of polymer science. Part A, Polymer chemistry》2002,40(24):4530-4537
Co2(CO)8 catalyzes the ring‐opening copolymerization of propylene oxide with CO to afford the polyester in the presence of various amine cocatalysts. The 1H and 13C{1H} NMR spectra of the polyester, obtained by the Co2(CO)8–3‐hydroxypyridine catalyst, show the following structure ? [CH2? CH(CH3)? O? CO]n? . The Co2(CO)8–phenol catalyst gives the polyester, which contains the partial structural unit formed through the ring‐opening copolymerization of tetrahydrofuran with CO. The bidentate amines, such as bipyridine and N,N,N′,N′‐tetramethylethylenediamine, enhance the Co complex‐catalyzed copolymerization, which produces the polyester with a regulated structure. Acylcobalt complexes, (RCO)Co(CO)n (R = Me or CH2Ph), prepared in situ, do not catalyze the copolymerization even in the presence of pyridine. This suggests that the chain growth involves the intermolecular nucleophilic addition of the OH group of the intermediate complex to the acyl–cobalt bond, forming an ester bond rather than the insertion of propylene oxide into the acyl–cobalt bond. Co2(CO)8? Ru3(CO)12 mixtures also bring about the copolymerization of propylene oxide with CO. The molar ratio of Ru to Co affects the yield, molecular weight, and structure of the produced copolymer. The catalysis is ascribed to the Ru? Co mixed‐metal cluster formed in the reaction mixture. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4530–4537, 2002 相似文献
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This article reviews recent discovery and progress of copolymerization of CO with cyclic monomers such as methylenecyclopropanes and propylene oxide promoted by transition metal complexes. 2-Aryl-1-methylenecyclopropanes react with CO in the presence of the Pd catalyst under mild conditions (1 atm, room temperature) to afford the polyketones. The reaction involves alternating insertion of the two monomers and opening of the three-membered ring of the cyclic monomers. Mechanistic study of the polymer growth revealed that 2-aryl-1-methylenecyclopropane undergoes 1,2-insertion into the Pd–acyl bond and subsequent -alkyl elimination of the cyclopropylmethylpalladium group. A bicyclic methylenecyclopropane, 7-methylenebicyclo[4.1.0]heptane, also reacts with CO in the presence of the Pd complexes with diimine ligands to afford the polyketone with six-membered rings in the repeating unit. The NMR spectra of the polyketone indicate the regulated tacticity of the monomer units. Co complexes and a mixture of Co and Ru complexes with carbonyl ligands promote the copolymerization of CO with propylene oxide in the presence of amine additives under CO pressure at 50 atm. Structures of the produced polyesters vary depending on the reaction conditions. 相似文献