The role of excess water in acidic sol-gel polymerization of tetraethoxysilane(TEOS) using molecular dynamics simulation

Abstract

To study the role of excess water in acidic sol-gel polymerization of TEOS, structural changes in Si(OH)(4) and Si(OH)(4) with H2O were compared in the temperature range from 298 to 373 K and pressure range from 1 bar to 10 kbar using molecular dynamics (MD) simulation. The intermolecular interaction distance determined from a radial distribution function results is used as a criterion of bond formation between two Si(OH)(4) molecules. In the Si(OH)(4) system, the number and relative occupancy of large ring-like structures increases with pressure under all temperature conditions. In Si(OH)(4) with H2O, the formation of ring-like structure hardly occurs under all temperature and pressure conditions. Water hinders the formation of the ring-like structures due to excluded volume effects caused by its hydrogen bond to the silanol group. It can be deduced that the remaining water after full hydrolysis of TEOS retards gelation of TEOS solutions.