可控去乳化高稳定Pickering乳液的制备及其应用研究

Pickering emulsions, stabilized by solid particles in place of surfactants. have received considerable attentions in diverse fields due to their ultrahigh stability, low toxicity and well adjustable droplet size. However, the high resistance of Pickering emulsion against coalescence makes the demulsification of Pickering emulsion difficult. A large amount of energy is required to be inputted for the detachment of the solid particles from the interface as the result of the strongly irreversible absorption, which thus brings forth some disadvantages in some special application fields, especially where demulsification is necessary. Therefore, exploiting Pickering emulsions having both high stability and facile demulsification is significant. In this project, preparation of Pickering emulsions with high stability and facile destabilization is proposed. Specifically, amphiphilic mixed-shells polymer particles with cross-linked cores by dynamic covalent bond (DCB), named dynamic mixed-shell polymeric particles, and amphiphilic graft copolymers with heterografted chains that are tethered on the main chain by DCB, will be firstly synthesized. The produced dynamic mixed-shell polymeric particles and heterografted copolymers will then be used as emulsifiers to stabilize emulsion. Owing to the polarity difference between oil and water, the dynamic mixed-shell polymeric particles and heterografted copolymers can form Janus-like structures at the liquid-liquid interface, which will contribute to a remarkable enhancement in emulsion stability. At the same time, the absorbed polymer particles can be dissociated rapidly into individual polymer chains upon altering the surrounding conditions, such as pH, and the stabilized Pickering emulsion can thus be facilely destabilized. Therefore, this proposal presents a new manipulation on emulsion stability and is expected to provide a useful guidance in the fields of oil recovery, catalysis, drug delivery, and so on. Compared with Janus, the outstanding advantage is that well-defined emulsifiers proposed in this project can be synthesized efficiently.

Pickering 乳液在采油、食品等众多领域有重要应用。具有合适粒径及较好表面润湿性的粒子及其稳定的Pickering 乳液近年来备受关注。由于粒子被强烈地吸附在两相界面, 粒子从界面脱吸附需要大量能量输入，导致去乳化难，这给Pickering乳液在某些领域的应用带来不便。本申请针对此问题提出采用两亲性核动态共价键交联杂壳聚合物粒子(动态杂壳聚合物粒子)或两亲性动态杂接枝共聚物为乳化剂制备稳定性好且去乳化可控的Pickering乳液。由于油水两相极性存在差异，动态杂壳聚合物粒子不同的壳或动态杂接枝共聚物的不同接枝支链在两相界面发生相分离，形成似Janus结构，从而提高乳化剂乳化活性及乳液稳定性。改变外界环境条件，破坏动态共价键，解离界面上吸附的聚合物(或粒子)，可实现Pickering 乳液快速、方便地去乳化。相比较Janus粒子，本申请项目所提出的乳化剂可高效制备，结构易于调控。

本研究项目基于可控去乳化高稳定Pickering乳液制备及应用开展研究。主要内容包括：(1)具有单一或多重刺激响应性聚合物粒子的制备、结构及形态表征。合成了一系列结构上包含动态共价键的聚合物。 通过超分子相互作用制备了一系列刺激响应性聚合物粒子。对聚合物粒子的结构及刺激响应性结构转变进行了研究；(2)刺激响应性Pickering乳液制备。以构筑的刺激响应性聚合物粒子为乳化剂制备了一系列具有单一刺激或多重刺激响应(包括温度，pH, 葡萄糖，光)的Pickering乳液。对乳化剂粒子的乳化活性及乳液的刺激响应稳定性进行了研究；(3)刺激响应性乳液应用探索研究。以构筑的刺激响应性Pickering乳液为模板，开展了高分子量双刷型共聚物高效制备、表面富含氨基的PS微球的制备以及油水两相界面异相催化反应研究。以上研究显示：(1) 具有星状或不对称棒状的聚合物粒子具有较好的界面活性，可在较低的粒子含量条件下获得高稳定的Pickering乳液；(2) 采用兼具刺激响应性和高界面活性的聚合物粒子为乳化剂是制备可控去乳化高稳定Pickering乳液的有效途径。吸附在两相界面的聚合物粒子在外界刺激作用下因结构发生变化失去界面活性，从两相界面脱吸附，导致Pickering乳液破乳；（3）刺激响应性粒子稳定的Pickering乳液在功能材料制备、异相反应领域具有独特优势。利用包含可逆动态共价键聚合物粒子在两相界面密堆积的特点，可高效制备出表面含大量功能基团(如氨基)的中空微球。这类微球在吸附、催化剂负载方面具有重要应用。可控去乳化Pickering乳液用于异相催化反应器，产物分离方便且催化反应器可循环利用。本项目研究成果丰富了Pickering领域研究，为Pickering应用拓展奠定基础。