Continuous-flow synthesis of polymethylsilsesquioxane spheres in a microreaction system

Abstract

A continuous-flow strategy based on the microreaction system is developed for the synthesis of monodispersed polymethylsilsesquioxane (PMSQ) spheres via one-step sol-gel method. Methyltrimethoxysilane (MTMS) and ammonium hydroxide (NH4OH) were used as silicon source and catalyst, respectively. The microreaction system includes three parts: a microdispersion device for the rapid hydrolysis of MTMS, a tubular reactor for subsequent condensation and fast growth of the particles, and a stirring reactor for final aging process. The effects of synthesis parameters on the particle size and size distribution were explored, mainly including the flow rates of ammonia solution and MTMS, concentration of NH4OH, solvent composition, and collection time of the reaction suspension. The particle size could be tuned from several hundred nanometers to a few microns with narrow particle size distribution. In addition, the operational stability of the continuous-flow microreaction system was also investigated. The continuous-flow process presents a high level of controllability, stability, and robustness, while enabling fast and reproducible scaling of laboratory results into large-scale production.