序列可调接枝共聚物及其衍生物的控制合成及性能研究

Sequence-regulated polymers can be regarded as an important application of Bionics in polymer design and synthesis. By taking advantage of the notion of sequence regulation in polymer design, this project aims at controlled synthesis and properties of novel multicomponent, multiblock, and multidensity graft copolymers and their derivatives with alternating pendent chains via controlled polymerization and post-polymerization modification, in which "grafting through" and "grafting from" approaches will be efficiently used for the synthesis. To this end, alternating copolymerization of styrenic and maleimidic comonomers is used to introduce various alternating grafts, and chain extension processes are applied to generate multiblock graft copolymers. Generally speaking, side chains comprise poly(ethylene glycol), biodegradable polyesters, and stimuli-responsive segments generated by controlled radical polymerization, and the regular sequences in pendent chains primarily involve A-alt-B, A-alt-BC, AA-alt-BC, AB-alt-CD and A-alt-Bx via alternating linkage, in which A, B, C and D mean various graft chains, and x is the graft number. On this basis, effects of some factors involving chemical composition, grafting density, and regular sequence of building blocks on physicochemical properties of graft copolymers will be investigated, and their potential applications in advanced functional materials involving stimuli-responsive multiphase materials, multifunctional materials, and nanocarriers for multi-order drug releases will be explored. The implementation of this project can not only promote the sustainable development of current polymer chemistry but enhance mutual understanding on the internal corelations among structure, property and application of sequence-controlled graft copolymers.

序列调控聚合物可归结为仿生科学在高分子设计合成中的一项重要应用。本项目将序列调控概念融入分子设计，采用grafting through和grafting from等技术控制合成多组分、多嵌段、多密度三大类含有序侧链接枝共聚物及其衍生物，并研究聚合物的性能和潜在应用。主要采用苯乙烯-马来酰亚胺交替共聚合构筑接枝侧链的交替序列，侧链化学组成主要为聚乙二醇、生物降解型聚酯和刺激响应链段，侧链序列主要为A-alt-B、A-alt-BC、AA-alt-BC、AB-alt-CD和A-alt-Bx（A、B、C、D为接枝侧链，x为链段数）。考察化学组成、接枝密度、模块序列等因素对接枝共聚物物理化学性能的影响，探索它们在刺激响应型多相材料、多功能材料、多级释放纳米载体等材料领域的应用。本项目的实施将有力促进高分子合成化学的可持续性发展，同时加深对于序列规整接枝共聚物结构-性能-应用内在关系的理解。

序列调控聚合物能部分模仿复杂生命体系的序列结构和多重功能，并可望在智能生命和高分子科学之间搭建一座重要的桥梁，因此在近年来受到了广泛关注。本项目将序列调控概念融入大分子设计，结合可控聚合和连接化学制备了多组分、多嵌段、多密度三大类含有序侧链接枝共聚物及其衍生物（接枝嵌段含线型、环状或支化型主链和线型、V型或星形侧链），并考察了化学组成、接枝密度、模块序列和拓扑结构等因素对聚合物物理性能的影响。各种聚合物主要包括：1）主链为苯乙烯-马来酰亚胺交替共聚物、嵌段数为1-5的接枝共聚物及其梳状-线型嵌段共聚物，侧链序列主要为A-alt-BC、AB-alt-C2、AB-alt-CD和A-alt-Bx（A、B、C、D为接枝侧链，x = 1，2，4，8）；2）兼具线型和V型侧链、接枝密度可调的四嵌段和六嵌段共聚物；3）主链共聚单元呈交替序列或统计分布的线型和环状接枝共聚物；4）接枝密度和主链序列可调的接枝共聚物；5）含刺激断裂键或可后修饰单元的线型和支化接枝共聚物。研究结果表明，外界刺激和分子裁剪等手段对聚合物的溶液性能和聚集行为具有显著影响，部分样品具有独特的微相分离行为、自组装性能和刺激响应性，并在多相材料、多功能材料、多级释放纳米载体等方面具有一定的应用前景。特别是发现了主链为P(St-alt-MI)、侧链为PNIPAM和PDMA的三嵌段接枝共聚物的聚集行为具有显著的温度和同位素溶剂依赖性。从室温逐渐增加至65 oC时，聚合物水溶液只呈现一个LCST转变，形貌为胶束和纳米囊；而在重水中呈双重LCST转变，升温时出现多级形貌转变，先后为球形胶束-纳米碗-囊泡-椭球形胶束-纳米棒-薄膜-纳米带-纤维状胶束和小胶束聚集体等形貌。本项目为接枝聚合物及其衍生物提供了多种普适性强的合成方法，有力促进了高分子合成化学的可持续发展，同时部分揭示了主链和侧链序列、拓扑结构等因素对接枝共聚物物理性能的影响。