Experimental Technology and Management

界面聚合是合成高性能高分子材料的常用聚合方法，但受限于原位观测和表征手段，界面聚合过程中微观反应动力学及聚合物的结构演变一直难以深入研究。该实验基于聚集诱导发光效应，利用激光扫描共聚焦显微镜对界面聚合反应过程的不同阶段进行实时荧光成像，通过对荧光图像进行定量分析，研究了聚合过程中聚合物的生成机制及其微观结构演变过程，揭示了界面处聚合物“疏-密-疏”的结构分布及聚合物结构与单体浓度的关系。该原位实时观测与全程可视化表征新方法可为界面聚合机理研究提供可视化平台，同时为功能聚合物的制备提供理论指导。

[Objective] As an important instrument for imaging research, the laser scanning confocal microscope has been gradually applied in the field of polymer science, such as polymer multicomponent systems, polymer particles, polymer films, self-assembly of block copolymers, controlled release of drugs, and the characterization of hydrogel. Interfacial polymerization is a common approach for synthesizing high-performance polymer materials. However, owing to the limitations of in-situ observation and characterization methods, the kinetics of polymerization and the evolution of the polymer structure during interfacial polymerization are difficult to explore in depth; hence, accurate control of the polymer structure by adjusting the polymerization conditions is difficult. [Methods] To overcome this problem, the aggregation-induced emission effect is used to realize in-situ and real-time observation of the entire interfacial polymerization process. Based on the environmental sensitivity of the fluorescent aggregation-induced emission moiety, clear images of the polymer are obtained by laser scanning microscope, and its structural evolution is characterized. In this experiment, tetrakis(4-aminophenyl) ethylene and toluene diisocyanate are selected as monomers for interfacial polymerization to produce polyurea in the alkane and ionic liquid solvent system. By dissolving tetrakis(4-aminophenyl) ethylene in ionic liquid and toluene diisocyanate in alkanes, the interfacial polymerization takes place at the stable alkane–ionic liquid interface and high fluorescent polymers are generated in a homemade device. A collection of images of the polymerization system colored by fluorescence intensity is obtained by the laser scanning confocal microscope. The effects of reaction time and monomer concentration on polymer growth are studied. The thickness and intensity distribution of the fluorescent region are analyzed by the affiliated software, such that the variation of thickness and density of the generated polymer could be clearly illustrated. [Results] The results showed that the fluorescent polymer continuously extends from the alkane solution to the ionic liquid phase, indicating that toluene diisocyanate has a strong tendency to diffusion, and the growth of a polymer layer occurs in the ionic liquid. With the further extension of polymerization time, the formed polymer hindered the diffusion of toluene diisocyanate; therefore, the reaction rate decreased slowly in the later stage. In addition, the experimental results showed that different monomer feed ratios can produce polymers with different microstructures. At the lower concentration of tetrakis(4-aminophenyl) ethylene, the fluorescence intensity of polymers grows slowly and is weaker than that at high concentrations, indicating that the overall polymer is less dense because of the lack of tetrakis(4-aminophenyl) ethylene. While under the same polymerization time, the higher concentration of tetrakis(4-aminophenyl) ethylene is accompanied by a faster polymerization rate and the polymer with higher fluorescence intensity is produced in a short time. By controlling the concentration and proportion of the two monomers, the structure of the polymer obtained by interfacial polymerization can be designed to achieve precise control of the polymer structure and performance. [Conclusions] Based on the high-resolution fluorescence imaging by laser scanning confocal microscope and the aggregation-induced emission effect, this study established a new method for the in-situ and real-time visualization of the interfacial polymerization reaction process, which can provide useful guidance for the regulation of interfacial polymerization systems or provide reference for the design and preparation of functional polymer materials.