Elastin-based side-chain polymers:: Improved synthesis via RAFT and stimulus responsive behavior
Elastin-based side-chain polymers:: Improved synthesis via RAFT and stimulus responsive behavior
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DOI：
10.1021/ma070527x
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发表时间：
2007-08-21
期刊：
影响因子：
5.5
通讯作者：
Cameron, Neil R.
中科院分区：
文献类型：
--
作者：
Fernandez-Trillo, Francisco;Dureault, Alex;Cameron, Neil R.
采用可逆加成-断裂链转移（RAFT）聚合法，通过五肽缬氨酸-脯氨酸-甘氨酸-缬氨酸-甘氨酸（VPGVG）的甲基丙烯酸酯衍生物的聚合制备了弹性蛋白基侧链聚合物（EBP）。聚合反应以受控的方式进行，得到具有窄分子量分布（多分散指数1.03-1.23）的聚合物，并且分子量与从所获得的转化率的初始单体：引发剂比率预测的那些分子量良好一致。所得聚合物的二硫酯端基通过与偶氮引发剂衍生的自由基反应而除去。在不同pH（1.5-5.1）和聚合物浓度（0.11-0.97 mg/mL）的溶液中以及对于不同聚合度（29-88个重复单元）的聚合物，研究了如此获得的一系列EBP的低临界溶解温度（LCST）行为。这些EBP的行为类似于线性多肽，称为弹性蛋白样肽（ELP）;转变温度随着聚合物浓度和分子量的增加而降低。与ELP不同，但与先前报道的EBP相同，观察到转变温度对pH的强烈依赖性，这是由于肽侧链中C-末端残基的羧酸的存在。然而，发现这里描述的EBP和之前报道的EBP之间存在显着差异，关于在给定pH值下的转变温度及其随分子量的变化。这些变化归因于本文所述的聚合物（较高分子量均聚物）与先前报道的那些（具有短EBP A嵌段和PEG B嵌段的A-B-A三嵌段共聚物）之间的结构差异。
Elastin-based side-chain polymers (EBPs) were prepared by the polymerization of a methacrylate derivative of the pentapeptide valine-proline-glycine-valine-glycine (VPGVG) using reversible addition-fragmentation chain transfer (RAFT) polymerization. The polymerizations proceeded in a controlled manner, yielding polymers with a narrow molecular weight distribution (polydispersity indices 1.03-1.23) and molecular weights in good agreement with those predicted from the initial monomer:initiator ratio for the conversion obtained. The dithioester end groups of the resulting polymers were removed by reaction with azo initiator-derived radicals. The lower critical solution temperature (LCST) behavior of the series of EBPs so obtained was investigated in solutions of varying pH (1.5-5.1) and polymer concentration (0.11-0.97 mg/mL) and for polymers of different degrees of polymerization (29-88 repeating units). These EBPs behaved similarly to linear polypeptides, known as elastin-like peptides (ELPs); the transition temperature decreased with increasing polymer concentration and molecular weight. Unlike ELPs, but in common with previously reported EBPs, a strong dependence of transition temperature on pH was observed due to the presence of the carboxylic acid from the C-terminal residue in the peptide side chains. Significant differences between the EBPs described here and those reported earlier were found, however, regarding the transition temperature at a given pH and its variation with molecular weight. These variations are attributed to differences in architecture between the polymers described here (higher molecular weight homopolymers) and those reported earlier (A-B-A triblock copolymers with short EBP A blocks and a PEG B block).