Preparation of mesoporous silica films with fully aligned large mesochannels using nonionic surfactants

Mesoporous silica films with uniaxially aligned large-sized mesochannels were prepared using nonionic alkyl poly(ethylene oxide) surfactants and a rubbing-treated polyimide coating. Although the increment of the pore size was small as long as conventional alkylammonium surfactants were used, the use of nonionic surfactants with poly(ethylene oxide) headgroups led to successful enlargement of the mesochannels. The directional distribution of the mesochannels in the films, which is estimated by in-plane X-ray diffraction, was very narrow and was comparable with that in the oriented mesostructured silica films prepared using hexadecyltrimethylammonium chloride as a templating agent. The distribution of the alignment direction of the mesochannels is nearly independent of the nature of the hydrophilic headgroup, but is slightly affected by the alkyl-chain length of the surfactants used. These results indicate that the alignment of the mesochannels is determined by the hydrophobic interactions between the oriented polymer chains of the rubbed polyimide and the surfactant tail groups.