Three-Dimensional Observation of Phase-Separated Silica-Based Gels Confined between Parallel Plates

Methyl-siloxane gel and silica gel with co-continuous structure derived from methyltrimethoxysilane (MTMS) and tetramethoxysilane (TMOS) were synthesized in two-dimensional (2D) confined spaces by inducing spinodal decomposition during the sol−gel transition. The resultant macroporous gel morphology was three-dimensionally examined by laser scanning confocal microscopy (LSCM), which revealed that the 2D confined gels have a layered structure. At the interface between MTMS- or TMOS-derived gel and a hydrophobic surface, the skin layer has formed by complete wetting by methylsiloxane and silica phase. In the near-surface region, a cylindrical columnar gel skeleton has formed only in the MTMS system. The volume fraction of gel phase oscillated near both hydrophobic and hydrophilic surfaces because of the attractive interactions between polymerizing siloxane and surfaces or shrinkage during aging stage.