Polymer substrates are widely used in the flat-panel-display industry because of their flexibility, light weight, and high power efficiency. However, the lower glass-transition temperatures and thermal stability and higher water/oxygen permeation of cycloolefin copolymers (COCs) constrain their applications in display substrates. In this research, COC/tetraethyloxysilane (TEOS) hybrids were synthesized via a sol-gel process. Differential scanning calorimetry indicated that the glass-transition temperature of the hybrids was higher than that of neat COC and rose significantly as the TEOS content was increased from 1 to 15 wt %. According to an analysis of IR spectra, the fraction of hydrogen-bonded carbonyl groups in the hybrids increased as the TEOS content increased. This meant that the interfacial interaction contributed by hydrogen bonds for the COC/TEOS hybrid system increased as the TEOS content increased from 1 to 15 wt %. On the basis of scanning electron microscopy, the number of dispersed droplets of silica increased as the content of TEOS increased. The decomposition temperatures of the hybrids, investigated with thermogravimetric analysis, were not affected significantly by the addition of TEOS. (c) 2007 Wiley Periodicals, Inc.