高分子冻胶的结构调控和功能拓展

Cryogels have interconnected super-macroporosity, excellent mechanical properties and high fluid throughput and can be used in bioengineering, medicine and drug, catalyst and energy areas. Keep in mind, during the freezing process, the solvent crystalizes and the gelation occurs. Different from common gels, the gelation of cryogels occurs upon the bulky crystallization of solvent insides. It has been well-established that solvent crystal induced porosity, un-frozen liquid microphase and cryo-concentration of the solutes are the key points to influence cryogel formation and porosity morphology. However, those effects fail in accounting absolutely for the characteristics of cryopolymerization, such as the rather rapid rate even under freezing point of the solvent. Through different gelation mechanism and synthetic chemistry combining with the choice of reaction medium, various polymeric cryogels have been obtained. However, there are still more possibility to modulate the chemical composition, crosslinked architecture and porosity morphology. In this project, we will emphasize our concentration in this aspect, based on the research results of synthetic chemistry of polymeric cryogels and the implementation of physical principle of liquid crystallization. We believe firmly that, copolymerization and network-grafting will achieve different polymeric cryogels with multi-components and various network-grafting architectures, uni-directional freezing and nucleation agents will result in the regular alignment of pores while the interpenetrating double pore-netowrk cryogels will be obtained by adjusting the interaction between the first pore-wall and the solvent used for the second pore-network. Our expected research outcomes will help to build a synthetic platform to regulate the hierarchical structure of polymeric cryogels and greatly improve their performances.

冻胶是具有相互贯通超大孔结构、优良机械性能和高流体通量的凝胶，凝胶化过程在溶剂整体结晶条件下完成，可应用于生物工程、医疗医药、催化和能源等领域。溶剂结晶致孔、溶剂晶体中的液相微区、成胶物质在液相微区的富集是冻胶形成和决定冻胶结构的关键因素，但是尚不能完全诠释冷冻聚合即使在冰点以下仍具有较高速率等现象。使用不同溶剂介质、通过不同成胶途径和合成方法，已经获得了许多类型的高分子冻胶，但是高分子冻胶在组成、交联结构和孔结构等方面还有调控余地。申请项目以高分子冻胶的合成化学作为基础，结合溶剂结晶的物理学原理，着重进行高分子冻胶的高分子结构和孔结构的调控研究，采取共聚和交联接枝实现冻胶组成的多组分化和交联结构的多样化，通过单向冻结和成核剂诱导实现孔道排列的规整化，通过改变第一网络孔壁和第二网络反应介质的亲合性获得互穿的双重网络冻胶，从而构建调控高分子冻胶多层次结构的合成方法，拓展高分子冻胶的功能。

冻胶是具有相互贯通超大孔结构、优良机械性能和高流体通量的凝胶，可应用于生物工程、医疗医药、催化和能源等领域，其凝胶化过程在反应介质整体结晶条件下完成，一般在介质溶剂冰点以下实施。溶剂结晶致孔、溶剂晶体中的液相微区、成胶物质在液相微区的富集是冻胶形成和决定冻胶结构的关键因素，但是冷冻聚合即使在冰点以下仍具有较高速率这一现象的本质有待诠释，目前冷冻聚合仅局限于烯烃的自由基链式聚合，冻胶的孔道结构的形成机制和调控还有很多未知，冻胶材料的应用前景有待进一步开拓。在项目执行期间，围绕上述问题，我们开展了多项研究工作。首先，我们将冷冻聚合由烯烃的自由基链式聚合拓展到N-羧基--氨基酸酐（NCA）的开环聚合和苯胺的氧化偶联聚合，首次报道NCA冷冻聚合的活性特征，发现丙烯酰胺的自由基聚合和苯胺的氧化偶联聚合可以同步进行，这一结果与苯胺的自由基链式聚合阻聚作用不相吻合。其次，采用不同的反应途径，制备出不同类型的多组分高分子冻胶和杂合冻胶，通过改变组分、冷冻条件和聚合温度对冻胶多层次结构进行了有效调控，如孔道结构、孔壁厚度、孔壁取向和组分分布。最后，对多种冻胶材料的性能和应用开展研究，杂合金属纳米粒子的冻胶材料可有效地催化p-硝基苯酚和染料化合物的还原，疏水性冻胶材料能高倍率、快速吸附不同油品，由取向聚丙烯酰胺冻胶和杂合石墨烯的冻胶组合的蘑菇状器件可有效地进行不同品质水的光热蒸发，冻胶材料因其内部多孔、表面粗糙的特性而表现出良好的摩擦起电性能。该项目虽然取得一些初步的研究结果，但是还有许多相关问题未能解决，如多重孔壁结构的冻胶制备、冻胶孔道结构的准确调控等，部分研究结果还需进一步完善。