Sol-gel derived mesoporous silica films using amphiphilic triblock copolymers

Mesoporous silica films have been synthesized by modifying the sol-gel method in the presence of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) block copolymers as structure-directing agents. Depending on the types of block copolymers, mesoporous silica films with different mesostructures, pore sizes and porosities have been formed. When block copolymers having relatively low average molecular weights were used, evaporation induced self-assembly was observed and then calcination induced structural transformation occurred. While only evaporation induced self-assembly was observed when block copolymers with larger average molecular weights were used. Pore sizes of the films increased with increasing the average molecular weight of block copolymers. Chemical modification using hexamethyldisilazane vapor made it possible to obtain the hydrophobic pore surface of the films. The dielectric constant of the films fairly depended on the porosity of the films. The dielectric constants of about 1.9-2.1 were obtained for the films with the porosity of about 65 vol.%. (C) 2003 Elsevier B.V. All rights reserved.