Silica-containing polyimide (PI-Si) crosslinked hybrid films are synthesized and applied to gas separation application. The PI-Si hybrid films are prepared from 4,4'-diaminodiphenyl ether (ODA), 3, 3'-oxydiphthalic anhydride (ODPA), p-aminophenyltrimetboxysilane (APTS), and phenyltrimetoxysilane (PTS). The monomer of monoamide APTS is used to modulate the block chain length of ODA-ODPA and then form bonding between PTS and ODA-ODPA phases. In the series of xASPI (where x indicates the molecular weight (in kg/mol) of PI block chain length of ODA-ODPA and ASPI denotes PI modified with APTS) hybrid films, the glass transition temperature (T,,) increases and a-relaxation damping peak intensity decreases with the increase of APTS content. Meanwhile, the gas permeabilities, Of O-2 and N-2 of xASPI films are slightly higher as compared with pure PI. The other series of (5AS-y-S)PI (5ASPI incorporates with PTS and y is the weight of PTS) hybrid films, the properties of T., density, and alpha-relaxation damping peak intensity are decreased with increasing the PTS content. However, higher O-2 and N-2 gas permeabilities, and O-2/N-2 selectivity are achieved by increasing the PTS content in (5AS-y-S)PI hybrid films. (c) 2007 Wiley Periodicals, Inc.