油水界面上环境刺激响应微凝胶高分子胶体粒子的原位研究

Stimuli-responsive microgel particles have been successfully employed to stabilize emulsion droplets, allowing controlled stabilization and destabilization of emulsions in responding to external stimuli. Such so-called "smart" emulsions have a wide range application in various industrial processes, such as fabrication of foams, crude oil extraction and food industry, thereby sparking broad attentions. Whilst microgel-stabilized emulsions have been well described in the literatures, the mechanisms that govern emulsion stability using responsive microgels are still not yet understood. In particular, the role played by microgel particles at interfaces still presents crucial open questions that can be answered only by direct visualization of the microgels in situ at the interface. In this project a new approach has been developed to investigate the correlation between physical behaviors of microgel particles at fluid interface with the emulsion stability. We will first prepare the micron-sized microgel particles that will be directly imaged by means of our high spatial-temporal resolution confocal microscope to obtain the particle interfacial microstructures and packing behaviors. By systematically and quantitatively analyzing the Brownian motion of the microgel particles using the combination of image processing and particle tracking techniques, we will try to clarify the correlation between the basic physical properties (e.g., structure, wettability, charging and compositions) of the microgel particles, their interfacial behaviors in responding to the external stimuli, and interaction potentials to the resulting emulsion stability. The outcome of this project thereby will provide information that is not currently available and the obtained data would be very useful in the design of switchable emulsions for opening up new applications.

使用环境刺激响应微凝胶粒子稳定油水界面，可令乳液响应性的乳化或破乳，这种功能化的乳液在重要的轻、重工业生产过程中具有广泛的应用前景，其相关的研究是高分子、胶体界面学科的新研究方向。但因现有的研究手段无法原位表征油水界面微凝胶粒子微观状态以及粒子间的微观排列，致使对被其所稳定乳液的乳化、破乳的微观机制仍不清晰，阻碍了研究的发展。针对以上关键问题，本研究拟制备可被光学显微镜直接观测且构型可控的环境刺激响应微凝胶粒子，结合高时空分辨率的显微拍照和图像追踪手段，直接获取界面微凝胶粒子微观状态以及粒子间的微观排列。系统地探索微凝胶粒子自身物理化学性质（如：构型、浸润性、带电性和化学组成）以及粒子间的相互作用和相应乳液稳定性的内在关联，并原位的研究环境刺激诱导所导致粒子在界面上微观状态所发生的改变，从而在根源上阐明其相应乳液乳化、破乳的微观机制，从理论上指导新一代'智能'乳液的设计和研发。

以具有环境刺激响应性的微凝胶粒子作为稳定剂能够制备得到可响应性乳化或破乳的Pickering乳液，这类功能化乳液在燃料加工、石油运输等重工业领域及两相催化、药物靶向运输等新兴领域中具有广泛的应用前景。因此，近十几年来以微凝胶粒子稳定的Pickering乳液受到越来越多的关注。然而，现有的研究手段无法原位表征油水界面上微凝胶粒子微观形态及排列模式，使得对相应乳液乳化、破乳机制尚不明确，限制了在此类“智能”乳液可控设计方面的发展。. 本项目拟制备可被光学显微镜直接观测且构型可控的环境刺激响应性微凝胶粒子，结合高时空分辨显微拍照技术及图像追踪手段，原位监测界面微凝胶粒子微观形态及排列模式。从而系统探索微凝胶粒子理化性质（化学组成、构型、浸润性、电性等）及粒子间低维相互作用与相应乳液稳定性间的内在关联，进而阐明此类功能化乳液乳化、破乳机制，从理论上指导新一代“智能”乳液的设计和研发。项目所得成果如下：. 首先，成功制备了不同尺度、构型可控的聚（N-异丙基丙烯酰胺）（PNIPAM）微凝胶粒子。此系列构型可控微凝胶粒子的成功合成，为后续界面粒子微观行为的研究奠定了基础；. 之后，采用共聚焦显微技术，观察研究了微凝胶粒子在其稳定的正癸烷—水两相界面上的微观形态，发现其仅于pH响应条件下发生铺展变形，更新了目前对微凝胶粒子在油水界面上形变程度的认知；系统研究了由PNIPAM微凝胶粒子稳定的正庚烷—水两相界面行为与温度的关系，发现界面粒子分别在低于、处于及高于体积相转变温度的条件下具有特定的排列模式，此结果对理解相应乳液乳化、破乳机制具有指导意义；. 结合高时空分辨显微拍照技术及图像追踪手段原位监测胶体粒子在二维油水界面上的微观行为，发现采用无助剂分散方法可有效避免油相中不稳定摩擦电荷的产生，从而实现界面粒子相互作用及排列模式的精确调控；. 最后，以胶体粒子稳定液—气界面制备得到非粘液滴，并将其应用于不对称颗粒的制备。. 本项目共发表SCI收录论文7篇，书籍章节一章，会议论文8篇。