Thermosensitive spontaneous gradient copolymers with block- and gradient-like features
Thermosensitive spontaneous gradient copolymers with block- and gradient-like features
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DOI：
10.1039/c7py00495h
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发表时间：
2017-09-14
影响因子：
4.6
通讯作者：
Harrisson, Simon
中科院分区：
文献类型：
--
作者：
Yanez-Macias, Roberto;Kulai, Ihor;Harrisson, Simon
采用可逆加成-断裂链转移（RAFT）共聚法制备了N-异丙基丙烯酰胺（NIPAM）与醋酸乙烯酯（VAc）的共聚物，NIPAM的摩尔分数为0.1 ~ 0.6，目标聚合度为100 ~ 250。所测得的动力学参数和得到的实验结果表明，该共聚体系导致“一锅法”合成的两亲性梯度共聚物，它具有类似的嵌段共聚物的温度响应和自组装特性，但有一些有趣的差异。它们在水中的自组装行为表明，形成的动态聚集体的溶解度的变化迅速响应，通过H-1 NMR光谱所揭示的，在相反的动力学冻结的聚集体形成的嵌段共聚物。此外，尽管它们的嵌段状组合物分布，这些共聚物显示出单一和宽的玻璃化转变，如通常在线性梯度共聚物中发现的。本文提出的合成方法可以很容易地适用于其他共聚单体体系，为嵌段共聚物的常规多步制备提供一种方便和经济的替代方案。
Reversible addition-fragmentation chain transfer (RAFT) copolymerization was used to prepare copolymers of N-isopropyl acrylamide (NIPAM) and vinyl acetate (VAc) with mole fractions of NIPAM ranging from 0.1 to 0.6 and targeted degrees of polymerization of 100 and 250. The measured kinetic parameters and obtained experimental results revealed that this copolymerization system leads to a "one pot" synthesis of amphiphilic gradient copolymers, which have thermoresponsive and self-assembly characteristics resembling those of the analogous block copolymers but with some intriguing differences. Their self-assembly behavior in water suggests the formation of dynamic aggregates which respond rapidly to changes in solubility as revealed by H-1 NMR spectroscopy, in contrast to the kinetically frozen aggregates formed by block copolymers. Furthermore, despite their block-like composition profiles, these copolymers display a single and broad glass transition, as is typically found in linear gradient copolymers. The synthetic approach presented in this contribution could readily be adapted to other comonomer systems to provide an accessible and economic alternative to the conventional multi-step preparation of block copolymers.