基于还原性高分子的含纳米金智能杂化微凝胶的制备及其原位凝胶化

In the traditional preparation of stimuli-responsive polymer/Au hybrid microgel by in situ reduction method, because of the addition of strong reductant like sodium borohydride, a large number of free Au nanoparticles are formed outside the microgel and the compositional design of the microgel is greatly limited as well. Aiming at solving the above problem, we propose to take advantage of the reducibility of some water-soluble polymers. First, temperature/pH-responsive microgels are synthesized consisting of reductive polymer by (seeded) soap-free emulsion polymerization. Then, temperature/pH/light-responsive polymer/Au hybrid microgels are prepared by in situ formation of gold nanoparticles in the presence of gold precursor without any additional reductant. At the same time, we plan to, for the first time, prepare injectable traditional hydrogel containing gold nanoparticles through the temperature and pH-induced in situ gelation of the formed polymer/Au hybrid microgels. In this project, we intend to prepare a series of stimuli-responsive polymer/Au hybrid microgels of different charge property with gold nanoparticles present at different sites. Their in situ gelation behavior will be studied in detail and the as-formed hydrogels will be further ionically, covalently and radiatively crosslinked by different methods. The research idea and strategy can be further used to fabricate other hybrid microgels and injectable hydrogels consisting of other polymers and noble metal components, promoting the development of relevant research areas.

原位还原法含纳米金智能杂化微凝胶的传统制备中，因硼氢化钠等外加还原剂的使用，极大地限制了微凝胶的组成设计并经常导致大量游离金粒子的生成。针对以上问题，我们提出利用（种子）无皂乳液聚合法，将不同性质的还原性高分子作为组分之一合成温度/pH双重敏感性微凝胶，再利用微凝胶本身所具有的还原性，在金前驱体的存在下原位合成纳米金粒子，从而形成含纳米金温度/pH/光多重敏感性杂化微凝胶。同时，首次以含纳米金杂化微凝胶为构筑单元，通过环境温度和pH的改变诱导其水分散液发生原位凝胶化，制备可注射含纳米金宏观水凝胶。本项目从粒子设计的角度，制备具有不同电荷性质、纳米金粒子分布于不同部位的智能杂化微凝胶，深入研究其原位凝胶化性能，并进一步通过不同的手段制备离子、共价和辐射交联含纳米金宏观水凝胶。项目的研究思路和研究方案亦可用于制备基于其它高分子和金属组分的智能杂化微凝胶及水凝胶材料，促进相关研究领域的发展。

原位还原法含纳米金智能杂化微凝胶的传统制备中，因硼氢化钠等还原剂的添加，极大限制了微凝胶的组成设计并经常导致大量游离金粒子的生成。针对以上问题，我们通过（种子）无皂乳液聚合法，将阳离子性的聚乙烯亚胺（PEI）和壳聚糖（CS）以及非离子性的聚乙烯基吡咯烷酮（PVP）作为组分之一，采用不同的合成路径，分别获得了正电性的具有核壳结构的聚（N-异丙基丙烯酰胺）/PEI（PNIPAM/PEI）、负电性的具有互穿高分子网络（IPN）结构和半互穿高分子网络（semi-IPN）结构的PVP/PNIPAM以及电中性的具有semi-IPN结构的PNIPAM/CS复合微凝胶。利用原位还原法，主要以含有还原性高分子的PVP/PNIPAM复合微凝胶为纳米反应器，在不添加任何小分子还原剂的条件下，通过改变体系pH值、反应温度和金前驱体的浓度获得了金纳米粒子大小可控的一系列环境敏感性PVP/PNIPAM-Au杂化微凝胶。这些杂化微凝胶具有温度可控的光学性质和催化性能。分别以PNIPAM/PEI、PVP/PNIPAM和PNIPAM/CS复合微凝胶为构筑单元，以流变学为主要研究手段，探讨了这些微凝胶分散液的原位凝胶化性能。发现当温度超过其体积相转变温度（VPTT）时，PVP/PNIPAM和PNIPAM/CS微凝胶在无机电解质电荷屏蔽和/或疏水缔合作用下发生原位凝胶化形成宏观水凝胶。凝胶化温度随微凝胶浓度的增大而降低，凝胶化时间随微凝胶浓度的增大和等温加热温度的升高而缩短。另外，发现PNIPAM/PEI微凝胶分散液在温度诱导下可进行胶体玻璃-液态、物理交联凝胶-液态和化学交联凝胶-液态间的相转变，呈现出了丰富的相转变行为。本项目思想可用来制备由其它还原性高分子和贵金属纳米粒子构成的智能杂化微凝胶及相应的宏观水凝胶。