基于RAFT聚合制备CO2刺激响应梯度聚合物及其可控自组装的研究

Gradient copolymer is a new kind of polymers emerging with the living polymerization techniques. It has been demonstrated that the gradual variation of monomeric compositions along the polymeric chains, which distinguishing from random and block copolymers has become an important factor affecting the self-assembly properties of polymers. In order to develop CO2 stimulus responsive self-assembly with more advanced structures and explore the rapid response mechanism of CO2 gas stimulation, this project intends to use a switchable RAFT chain transfer agent for controlling the homopolymerization of more active monomer Benzyl methacrylate (BzMA) and copolymerization between more active monomer 2-(Diethylamino)ethyl methacrylate (DEAEMA) and lower active monomer N-vinyl pyrrolidone (NVP) successively, producing a triblock copolymer with gradient segment in chain segment. The presence of a gradient segment enables the formation of multilamellar vesicles in aqueous solution. Under the stimulation of CO2 gas, the PDEAEMA segment in the gradient block will be protonated, and the hydrophilic-hydrophobic balance in the wall of vesicle will be partly changed, so as to realize the specific transformation of the assembly morphology and the controlled release of doxorubicin. At the same time, control group is carefully designed by synthesizing another triblock copolymer with similar molecular composition but not including a gradient block. It can be proved that this strategy would provide advantages for the construction of polymeric assemblies with more advanced structures and functional nanocarriers with higher sensitivity.

梯度共聚物是近年来伴随活性聚合方法而发展起来的一种新型共聚物。已有研究显示，两种单体单元在高分子链上的特殊梯度排布方式，已成为影响聚合物自组装性质的重要因素。为了发展结构更高级的CO2刺激响应组装体以及探索对CO2气体刺激的快速响应机制，本项目拟利用可切换型RAFT链转移剂，先后控制高活性单体甲基丙烯酸卞甲酯（BzMA）的均聚和高活性单体甲基丙烯酸二乙氨基乙酯（DEAEMA）与低活性单体乙烯基吡咯烷酮（NVP）的共聚，构筑一类内部含有梯度变化链段的三嵌段共聚物。梯度链段的存在使共聚物在水溶液中能形成多壁囊泡的组装体结构。在CO2刺激下，梯度嵌段中的PDEAEMA链段质子化，局部改变囊泡壁的亲疏水平衡，实现组装体形貌的特异性转变及药物阿霉素的逐级可控释放。同时，合成一类分子组成相近，但不含梯度嵌段的三嵌段共聚物对照组，证明梯度聚合物在构筑特殊形貌组装体和和快速应激响应性功能体方面的优势。

梯度共聚物是近年来伴随活性聚合方法而发展起来的一种新型共聚物。已有研究显示，两种单体单元在高分子链上的特殊梯度排布方式，已成为影响聚合物自组装性质的重要因素。为了发展结构更高级的CO2刺激响应组装体以及探索对CO2气体刺激的快速响应机制，本项目利用可切换型RAFT链转移剂，成功构筑一系列内部含有梯度变化链段的三嵌段共聚物，在CO2等气体刺激下研究组装体形貌的特异性转变。在此基础上，我们进一步发展了半连续加料法的梯度聚合物合成过程，极大地扩大了单体的适用范围，同时也丰富了梯度聚合物的结构种类，在CO2气体作用下，实现了特殊的纳米片层组装结构的制备。同时我们还进一步发展了CO2/air双重气体调控下组装体形貌的可控变化，在纳米尺度上分阶段模拟了肺泡的“成型-呼吸-凋亡”的全过程，为探索生命现象提供了重要依据。在本项目经费支持下共发表SCI论文17篇，包括Macromolecules、Chemical Communications、Polymer Chemistry等本领域重要期刊。本项目的研究成果揭示了梯度聚合物在构筑特殊形貌组装体和快速应激响应性功能体方面的优势，并探索了聚合物组成对体系组装形貌的影响规律，为高分子纳米组装体设计提供了新的思路。