刺激响应性高分子是指在外界环境发生较小的改变时，在结构和性质上产生较大改变的材料，能够将化学或者生化信号转化成光、热、电或机械力信号，反之亦然。为了能够对生命体的奥秘实现更深入的研究，发展新型的智能生物材料和纳米技术、研究新型刺激响应性高分子材料具有重要的意义。其中，具有活性氧响应性的高分子材料尤为重要。活性氧物种，作为广泛存在于生物体内的一类活泼物种，与很多疾病的产生都息息相关。近年来，关于活性氧响应高分子材料的研究可谓炙手可热，但活性氧响应高分子材料领域仍然面临很多问题。本论文主要关注以下三个科学问题：如何在实现同样响应灵敏性的同时，降低响应性分子的用量；如何实现生理条件下逐级响应性智能材料的构筑；能否寻找有机化学与硒/碲相关的常用反应，发展新型响应性材料。本文基于各种含硒/碲分子体系的设计，发展了各种具有活性氧响应性的组装体。主要取得了以下的成果：一、发展了共组装的普适方法，将含硒/碲分子和磷脂分子进行共组装，获得了具有活性氧响应性、生物相容性较好的共组装体体系。共组装的方法可以同时结合两种组装基元的优点，利用含硒/碲分子的响应性和磷脂分子的生物相容性，在降低含硒/碲分子用量的同时，为体系赋予同样灵敏的响应性。这部分工作提出的共组装，可以作为一种普适的方法，来实现多种响应性体系的构筑。二、利用共聚的方法，将硒/碲引入到同一个高分子当中，实现逐级活性氧响应性组装体的构筑。利用含硒分子和含碲分子对于活性氧的响应差异，该共聚物能够实现对活性氧刺激的逐级响应，高分子能够被逐级氧化。除了化学方法之外，利用电化学氧化的方法，改变氧化电压，同样能够实现逐级氧化响应。三、将有机化学中的亚硒砜消除反应应用到高分子领域，实现活性氧响应性可降解含硒高分子的构筑。不同于通常的主链含单硒高分子只能够在氧化条件下实现亲疏水性的改变，该含单硒高分子能够通过亚硒砜消除反应实现高分子链的可控降解。该反应同样适用于含碲分子，未来有望用于超灵敏活性氧响应性含碲可降解高分子体系的构筑。
Stimuli-responsive polymers are defined as polymers which could response to environmental change and undergo structural or qualitative changes. As a result, external chemical or biochemical signals could be transformed as light, heat or mechanical force, vice versa. To further reveal the secrets of organisms, it is significant to develop novel intelligent biomaterials and nanotechnology. One of the most important stimuli is reactive oxygen species (ROS). ROS, as a sort of reactive molecules or free radicals, play important roles in cell metabolism and are always related with many diseases. Recently, increasing studies on ROS responsive polymer materials are reported. However, there are still many challenges remained. The thesis is focused on three questions in the stimuli responsive material area: how to maintain the responsiveness with lower concentration of stimuli-responsive molecules, how to realize the fabrication of hierarchical responsive materials and how to develop novel responsive systems based on selenium/tellurium related organic reactions. Based on different sort of selemiun/tellurium molecules, we developed several ROS responsive assemblies. This work include three parts as shown below:(1) We developed a general coassembly method to fabricate ROS responsive systems based on the coassembly of selenium/tellurium-containing molecules and phospholipids, taking advantage of the responsiveness of selenium/tellurium-containing molecules and the biocompatibility of phospholipids. With a small amount of selenium/tellurium-containing molecules, the system could exhibit similar responsiveness. Coassembly could also be employed as a general method to fabricate different kinds of responsive systems. (2) We copolymerized both selenium and tellurium in one polymer chain, to realize the fabrication of hierarchical ROS responsive systems. Based on the different sensitivity of selenium and tellurium in ROS response, the copolymer could realize hierarchical ROS responsiveness and the polymer could undergo a stepwise oxidation process. Besides the chemical oxidation, the stepwise oxidation process could also be realized by electrochemical methods. (3) We successfully introduced the organic selenoxide elimination reaction to polymer chemistry and developd a ROS responsive degradable selenide-containing polymer. Different from previous monoselenide-containing polymer which could only be oxidized with the change of amphiphilicity, this system could realize ROS triggered controlled depolymerization and degradation of the polymer chains. This ROS responsive oxidation-elimination reaction could also be employed in tellurium-containing molecules, which could be utilized to develop novel ultrasensitive ROS responsive tellurium-containing polymer in future.
