Ordered mesoporous silica fibers: effects of synthesis conditions on fiber morphology and length

Abstract

Ordered mesoporous silica fibers offer potential industrial application in several areas including polymerization catalysis and separation. Understanding the effects of synthesis conditions on these fibers prepared by the interfacial self-assembly growth method is important to their production and application. The focus of this work is to understand the effect of two previously unstudied factors: silica source height (tetrabutylorthosilicate, TBOS) and the humidity, on the formation of ordered mesoporous silica fibers by the interfacial self-assembly method. Here the TBOS content, interface area, height of source, and humidity of the environment were varied to study their effect on fiber growth. The results show that the TBOS content and interface area do not have a significant impact on results of ordered mesoporous silica fibers. Increasing silica source height or environmental humidity, which lowers the water evaporation rate, gives silica fibers with lower length, less ordered inner pore structure and macroscopic morphology, and smaller pore size. Attempts to mix the growth medium eliminate the fiber morphology and yield gyroidal shapes. A mechanism that combines evaporation of water resulting in local concentration and surfactant, self-assembly, and reaction and diffusion of silica source is proposed to describe the formation of ordered mesoporous silica fibers.