共查询到20条相似文献,搜索用时 171 毫秒
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分别以D,L-乳酸和L-乳酸为原料制得D,L-丙交酯(D,L-LA)和L-丙交酯(L-LA);以辛酸亚锡为内酯开环聚合引发剂,用ε-己内酯(ε-CL)开环均聚合制备聚ε-己内酯,考察了引发剂用量、聚合时间和温度等对聚合产物特性黏数的影响。由ε-CL与D,L-LA和L-LA共聚合制得聚(ε-己内酯-D,L-丙交酯)和聚(ε-己内酯-L-丙交酯),并用傅里叶变换红外光谱、核磁共振氢谱、差示扫描量热法、X射线衍射等对聚合物的结构进行表征;力学性能测试结果表明,聚(ε-己内酯-L-丙交酯)具有很好的弹性和较高的断裂伸长率。 相似文献
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Amphiphilic heteroarm star‐shaped polymers have important theoretical and practical significance. In this work, amphiphilic heteroarm star‐shaped polymer was synthesized by the use of polyfunctional chain transfer agent via sequential free radical polymerization in two steps. First, conventional free radical polymerization of methyl methacrylate (MMA) initiated by 2,2′‐azobis (isobutyronitrile) (AIBN) was carried out in the presence of polyfunctional chain transfer agent, pentaerythritol‐tertrakis (3‐mercaptopropinate) (PETMP). At appropriate monomer conversion, about two‐arm s‐PMMA having two residual thiol groups at the chain center was obtained. Second, the s‐PMMA obtained above was used as macro‐chain‐transfer agent for free radical polymerization of acrylic acid (AA). The heteroarm star‐shaped polymer with the hydrophobic PMMA segment and the hydrophilic PAA segment was obtained. The successful synthesis of heteroarm star‐shaped polymers, (PMMA)2(AA)2, was confirmed by 1H‐NMR and its self‐assembly behavior in different solvents. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
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A new well-defined bisbenzoin group end-functionalized poly(ε-caprolactone) macrophotoinitiator (PCL-(PI)2) was synthesized by combination of ring opening polymerization (ROP) and click chemistry. The ROP of ε-CL monomer in bulk at 110 °C, by means of a hydroxyl functional initiator namely, 3-cyclohexene-1-methanol in conjunction with stannous-2-ethylhexanoate, (Sn(Oct)2), yielded a well-defined PCL with a cyclohexene end-chain group (PCL-CH). The bromination and subsequent azidation of the cyclohexene end-chain group gave bisazido functionalized poly(ε-caprolactone) (PCL-(N3)2). Separately, an acetylene functionalized benzoin photoinitiator (PI-alkyne) was synthesized by using benzoin and propargyl bromide. Then the click reaction between PCL-(N3)2 and PI-alkyne was performed by Cu(I) catalysis. The spectroscopic studies revealed that poly(ε-caprolactone) with bisbenzoin photoactive functional group at the chain end (PCL-(PI)2) with controlled chain length and low-polydispersity was obtained. This PCL-(PI)2 macrophotoinitiator was used as a precursor in photoinduced free radical promoted cationic polymerization to synthesize an AB2-type miktoarm star copolymer consisting of poly(ε-caprolactone) (PCL, as A block) and poly(cyclohexene oxide) (PCHO, as B block), namely PCL(PCHO)2. 相似文献
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A four‐armed star‐shaped poly(tetrahydrofuran) (THF) having a pentaerythritol unit at the center of the molecule was synthesized from photoinduced cationic copolymerization of THF and pentaeryithritol tetrakis(3,4‐epoxybutanoate) (PETE) in the presence of diphenyliodonium hexafluorophosphate. It was found that the molecular weight of the resulting polymer increases with increasing percent conversion and the rate of cationic polymerization of THF is remarkably increased by the addition of PETE when the concentration of PETE is kept much lower than that of THF. A similar enhancement effect was also observed in the photoinduced cationic polymerization of THF in the presence of epichlorohydrin (ECH). The enhancement effect of ECH and PETE was ascribed to the increased concentration of the cationic propagating species due to a rapid protonation process. The living nature was explained in terms of the stabilization of the cationic growing chain end by ion pair formation. Accordingly, the arm length of the polymer was determined by the molar ratio of THF and PETE. However, the polymer of well‐defined structure was only obtainable in the early stage of the reaction because chain transfer to the polymer process plays an important role when the concentration of the polymer becomes high. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2637–2644, 1999 相似文献
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以S-十二烷基-S’-(α,α’-二甲基-α’’-乙酸)-三硫代碳酸酯(DDMAT)为链转移剂,通过可逆加成-断裂链转移自由基聚合(RAFT)方法制备了窄分布的聚2-乙烯基吡啶。再以该聚合物为大分子链转移剂,引发苯乙烯的RAFT聚合,得到聚2-乙烯基吡啶-b-聚苯乙烯(P2VP-b-PS)的两嵌段共聚物。以P2VP-b-PS为RAFT试剂,合成聚2-乙烯基吡啶-b-聚苯乙烯-b-聚异戊二烯(P2VP-b-PS-b-PI)的三嵌段共聚物。运用1H NMR、IR和凝胶渗透色谱(GPC)等技术对产物的结构和分子量及分子量分布进行表征,采用原子力显微镜(AFM)观察三嵌段共聚物薄膜的微相分离结构。结果表明,所得三嵌段共聚物P2VP72-b-PS136-b-PI300分子量分布较窄(PDI=1.69),合成过程具有活性/可控聚合特征,聚合物薄膜经溶剂退火处理后出现了明显的微观相分离结构。 相似文献
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在甲基丙烯酸甲酯(MMA)单体中,以偶氮二异丁腈(AIBN)与I2反应原位合成α-碘代异丁腈(IIBN),进一步作为原子转移自由基聚合引发剂分别与CuCl、FeCl2.4H2O等催化剂,MA5-DETA、PMDETA等络合剂相匹配引发MMA的ATRP,同时又作为衰减链转移聚合(DT)的可逆链转移剂同步进行DT聚合。实验结果表明:所得聚合物分子量可控,分子量分布(PDI)很窄(1.05~1.25),引发剂效率较高。动力学的研究结果显示:分子量随转化率而增长;由Ln[M]0/[M]t对时间作图,呈现良好的线形关系,表明聚合过程中增长自由基浓度是一个恒定值,证明由IIBN引发的聚合是典型的活性自由基聚合;这种方法克服了极不稳定的在α-位带有吸电子基团的碘化物的购运和储存的困难。不失是一种简单,快捷,方便的方法。 相似文献
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2-溴代异丁酸-Ⅳ-丁二酰亚胺酯(NHS—BIBA酯)由2-溴代异丁酸和,v-羟基丁二酰亚胺通过酯化反应制得。以它为引发剂,2,2'-联吡啶(bpy)/CuBr为催化体系、水为溶剂,采用原子转移自由基聚合(ATRP)合成了带有功能基团的聚甲基丙烯酸二甲氨基乙酯(PDMAEMA)高分子。研究了引发剂、温度、反应时间、pH值和浓度对聚合产率的影响,利用凝胶渗透色谱(GPC)和核磁共振(1HNMR)测定了聚合物的分子量、多分散指数(PDI)和链结构。由GPC可知在最高产率下,Mn和Mw/Mn分别为8674和1.59,结果表明,NHS-BIBA酯引发的PDMAEMA实际数均分子量高于理论分子量,并具有低分散度,链结构上氢原子出峰符合特有的化学位移。 相似文献
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异端基遥爪聚乙二醇的传统合成方法是端基改性法,它是以同端基遥爪聚乙二醇为原料,对其端基进行改性,得到异端基遥爪聚乙二醇;而直接合成法是用含有不同双官能团的引发剂来引发环氧乙烷的阴离子开环聚合,获得异端基遥爪聚乙二醇,同时两活性端基还可以进一步改性,衍生出更多种类的异端基遥爪聚乙二醇。对异端基遥爪聚乙二醇的直接合成法、端基改性法和通用性合成方法的研究进展进行了综述。 相似文献
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Md. Zahangir Alam 《Polymer》2011,52(17):3696-3703
Azobenzene-functionalized star polymers were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. First, azobenzene-functionalized linear macro chain transfer agents (Macro-CTA) were synthesized by RAFT polymerization of 6-[4-(4′-Methoxyphenylazo)phenoxy]hexylmethacrylate (MAz6Mc) using 2-(2′-cyanopropyl)dithiobenzoate (CPDB) as RAFT agent in presence of AIBN as initiator in anisole. Subsequently, star azopolymers were synthesized by polymerization of a difunctional azomonomer, BMA2Az, with resultant Macro-CTA in presence of AIBN as initiator in anisole. Star azopolymers were characterized by GPC and spectroscopic methods. Thermal properties of star azopolymers were determined by DSC and TMA. Molecular weight versus conversion and molecular weight versus polymerization time attest to living polymerization characteristics. Photoisomerization behaviors of star azopolymers were studied by irradiation of both UV and visible light. Surface relief gratings were inscribed on star azopolymer films upon exposure to an interference pattern of (RCP + RCP) Ar+ laser. A diffraction efficiency of 20% was obtained by exposure of Star-8 K(2.6 K) polymer film to an (RCP + RCP) Ar+ laser for about 30 min. Surface relief grating structures were investigated by AFM and polarized optical microscopy. 相似文献
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New shape memory polymers with self‐healing behavior are obtained by thermoreversible Diels–Alder (DA) cross‐linking of a furfuryl group‐containing star‐block copolymer with 1,1′‐(methylenedi‐4,1‐phenylene)bismaleimide. The star‐block copolymer consisting of a 3‐arm polycaprolactone (PCL) core and a polyfurfuryl methacrylate shell is synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. For this, a 3‐arm macro‐RAFT agent based on PCL is converted with an appropriate amount of furfuryl methacrylate in the presence of a radical initiator. Films of the DA network are partly insoluble at ambient temperatures. After annealing at 120 °C the films become completely soluble because of the progressing retro‐DA reaction. Evaporation of the solvent and subsequent annealing at 60 °C restores the original insoluble state of the material. By means of a scratch test and tensile tests on cut and subsequently mended samples it is shown that the retro‐DA reaction facilitates self‐healing. Additionally, the films show pronounced shape memory effects with reasonable shape recovery and fixity ratios, which are attributed to the melting and crystallization of the PCL phase. 相似文献