Interfacial interactions and their influence to phase behavior in poly(vinyl pyrrolidone)/silica hybrid materials prepared by sol–gel process

Abstract

In this research, hybrid materials constructed by poly(vinyl pyrrolidone) (PVP) and inorganic tetraethyloxysilane (TEOS) or methyltriethyloxyslane (MTEOS) were synthesized via sol–gel process. From visual and scanning electron microscopic (SEM) observation, inorganic silicate was not separated from the organic phase in PVP/MTEOS hybrid system and in PVP/TEOS hybrid system with 20 wt.% or less TEOS content. With 40 wt.% TEOS content, microphase separation occurred; furthermore, phase separation and phase inversion can be observed with TEOS content increased to 60 wt.% or more in PVP/TEOS hybrid system. These results were confirmed by the variation of glass transition behavior. From infrared spectra analysis, hydrogen bonds were formed in both PVP/MTEOS and PVP/TEOS hybrid systems. However, higher hydrogen bonding interaction in PVP/TEOS did not induce higher compatibility as compared to PVP/MTEOS. This was due to the greater non-polar interaction between methyl group of MTEOS and polymer backbone in PVP/MTEOS hybrid system.