Properties of hybrid materials derived from hydroxy-containing linear polyester and silica through sol-gel process. I. Effect of thermal treatment

The transparent hybrid material, HLP/SiO2, was prepared by an in situ sol–gel process of tetraethoxysilane (TEOS) at 30°C in the presence of hydroxy-containing linear polyester (HLP) obtained by ring-opening reaction of diglycidyl ether of bisphenol A (DGEBA) with adipic acid under the catalyzation of triphenylphosphine (TPP). The hetero-associated hydrogen bonds between the HLP and the residual silanol of silica in the hybrids were investigated by FTIR spectroscopy. Upon heating the hybrid, the interfacial force between the HLP matrix and the silica network changed from hydrogen bonds into covalent Si—O—C bonds through dehydration of hydroxy groups in HLP with residual silanol groups in the silica network. The existence of covalent Si—O—C bonds was proved by solid-state 29Si-NMR spectra. Other properties such as tensile strength, glass transition temperature (Tg ), solubility, and thermal stability of the hybrids before and after heat treatment were studied in detail.