Sol−Gel Processing of Ordered Multilayers To Produce Composite Films of Controlled Thickness

Sol−gel processing of a multilayered film formed by the alternate adsorption of poly(diallyldimethylammonium chloride) and a synthetic silicate sheet mineral, Laponite RD, resulted in an interpenetrating composite network. Kinetic data indicate that the amount of material added due to sorption and gelation of tetraethyl orthosilicate (TEOS) reached a steady-state value within a day. Sol−gel growth occurred within the multilayer, with very little silicate being deposited at the surface. The resulting composite film showed the same order as an untreated multilayer, indicating that sorption and gelation did not disrupt the structural order of the multilayer. Curing the TEOS-treated films at 175 °C for 24 h to drive off excess water and complete the gelation process again resulted in an ordered composite structure. Cured films exposed to various levels of relative humidity demonstrated a dramatic decrease in swellability compared to an untreated multilayer.