| Mesoporous films have a wide range of potential applications which include photovoltaic devices, catalysis, separation membranes, sensors, and low-k dielectric for microelectronics. Mesoporous films with different morphologies can be synthesized by utilizing preformed polymer template films and introducing reactive precursors either through their vapor or dissolved in supercritical carbon dioxide (CO2). These methods are thought to have potential advantages over the traditional solution phase synthesis as self-assembly of the polymer and inorganic network formation are fully decoupled.;In this work, the influence of a homopolymer additive in block copolymer templates on the final morphology and modulus of mesoporous silica films is examined. The homopolymer additive concentration can significantly change the resulted mesopores ordering and robustness of the silica films. Meanwhile, the influence of CO2 on the synthesis of mesoporous silica films is investigated systematically as a function of pressure. A maximum in the average pore size is obtained near CO2 critical pressure with a gradient in pore size at the free surface of the films and a short gradient at the buried interface. To understand this maximum swelling near critical pressure of CO2, reactions are conducted at different temperatures and as a function of film thickness. The pore sizes at the interfaces in the films prepared near CO2 critical pressure increases significantly as the reaction temperature approaches CO2 critical temperature, while the extent of the gradients at both interfaces decreases as the film becomes thicker.;Moreover, the hydrolytic stability of silica films in biology relevant conditions is examined. Thin mesoporous silica films dissolve in phosphate buffered saline and their lifetimes can be extended from several hours using traditional sol-gel approaches to days by using CO2 processing for identical thickness. Last but not the least, diffusion kinetics of a reactive precursor into polymer films is investigated which provides insights to understanding the formation mechanism of inorganic films for desired applications. |
