大分子重氮偶合反应用于构建具有复杂链结构嵌段聚合物

Due to their unique architectures, the block copolymers with complex structures have shown many interesting properties, which can be used in many potential nanotechnological applications such as drug delivery systems, nanoreactors and others. Thus, finding facile and feasible synthetic methods to prepare these kinds of block polymers with complex architectures is consistently one of the desired goals in recent years.With the development of click chemistry and controlled radical polymerization (CRP),the combination of click chemistry and CRP techniques has been proved to be an efficient platform for the preparation of block copolymers among the synthetic strategies have been established.On the other hand, this approach needs reactive end groups to guarantee the high yield coupling reaction and avoid possible side reactions.The typical "click" reaction is 1,3-dipolar cycloaddition between polymeric blocks bearing functional terminal azide and alkyne functionalities using copper(I) as the catalyst, which has attracted considerable attention and been applied for linking different polymeric blocks. Finding other high-efficient coupling reactions is a necessary step to further develop this synthetic strategy.In this project, we will develop a novel modular strategy for the synthesis of block copolymers with complex architectures by macromolecular azo coupling reaction. Various types of macromolecular diazonium salts and polymeric blocks with coupling components will be designed and synthesized. The influences of solvents, position of the coupling groups and the chemical structures of the polymeric blocks on the macromolecular azo coupling reaction will be systematically studied. The optimized conditions for preparation of block polymers with complex architectures will be obtained. The polymers containing azobenzene linkage units may have potential application in the arena of colon-specific delivery systems.

利用高效大分子间反应(点击化学)与活性可控自由基聚合联用来制备具有复杂链结构的嵌段聚合物成为近年来的研究热点。目前常见击化学反应如叠氮化物与炔的环加成反应大都需要铜盐催化且反应条件较为苛刻。发展其它行之有效的大分子偶联新方法成为了目前高分子合成有关领域的一项重要目标。本项目拟利用具有高产率、高选择性、反应条件温和等特性的重氮偶合反应来高效偶联聚合物大分子链段，从而建立利用大分子重氮偶合反应合成具有复杂链结构嵌段聚合物的新方法。本项目将系统研究各类大分子重氮盐及含偶合组分聚合物的制备新方法，系统研究如溶剂、可偶合基团的位置及聚合物化学结构等对大分子重氮偶合反应的影响规律，得到大分子重氮偶合反应制备复杂链结构聚合物的适用条件，有关研究结果将为制备复杂拓扑结构聚合物开辟一条新途径。同时得到的含偶氮苯连接基团的系列嵌段聚合物有望用于酶催化还原的肠道药物可控释放载体。

有复杂链结构的聚合物在纳米科技、材料改性、生物医学等领域有广阔的应用前景，日益受到大家的重视。发展行之有效的大分子偶合新方法为制备复杂链结构的聚合物提供了重要途径。本项目发展了利用大分子重氮偶合反应制备两亲性嵌段共聚物的新方法，利用端基修饰或结合活性聚合的方式可以得到PEG或聚丙烯酸的线型或V型大分子重氮盐，利用包括ATRP，RAFT及NMP等活性可控自由基聚合得到了一端或分子中间带有可反应苯胺残基的聚合物，上述两种聚合物在有机溶剂如DMF中会发生大分子重氮偶合反应，从而非常简便及高效地制备了各种复杂链结构的聚合物。大分子重氮偶合反应形成的偶氮苯连接基团还同时带来了新颖的光或生物酶刺激响应性行为，为得到的聚合物材料提供了特殊功能性,在光信息存储、生物医药等领域有着潜在的应用价值。利用大分子重氮偶合反应还可以进一步实现天然大分子的化学改性，我们利用大分子重氮偶合反应可以高效的在碱木质素上引入PEG大分子链，从而高效的改进木质素的溶解性和可加工性，为木质素的高效利用和提高木质素附加值提供了一种新思路。