Periodic Mesoporous Organosilica Films with a Tunable Steady-State Mesophase

The mesophase formation in spin-coated periodic mesoporous organosilica (PMO) films aged at a controlled ambient humidity is investigated by time-resolved grazing-incidence small-angle X-ray scattering (GISAXS). The investigation demonstrates the existence of a tunable steady state in PMO spin-coated films. Thus, a film deposited at a relative humidity of 20 % has a lamellar mesophase, whereas a subsequent increase to 70 % leads to a phase transformation resulting in a P6₃ /mmc space group. On the other hand, an increase of the surfactant to organosilica molar ratio of between 0.26 and 0.31 results in films which at 70 % humidity form a mix of 2D and 3D hexagonal phases. A further increase of the surfactant amount leads to films with a 2D hexagonal phase. Finally, the different mesophases observed as a function of the solution aging emphasize the importance of the degree of polycondensation of the organosilica oligomers.