Publications

In-situ X-ray scattering study of continuous silica - Surfactant self-assembly during steady-state dip coating

Doshi, Dhaval D.; Gibaud, Alain; Liu, Nanguo; Sturmayr, Dietmar; Malanoski, Anthony P.; Dunphy, Darren R.; Chen, Hongji; Narayanan, Suresh; MacPhee, Andrew; Wang, Jin; Reed, Scott T.; Hurd, Alan J.; Van Swol, Frank; Brinker, C.J.

Inorganic mesoporous thin-films are important for applications such as membranes, sensors, low-dielectric-constant insulators (so-called low κ dielectrics), and fluidic devices. Over the past five years, several research groups have demonstrated the efficacy of using evaporation accompanying conventional coating operations such as spin- and dip-coating as an efficient means of driving the self-assembly of homogeneous solutions into highly ordered, oriented, mesostructured films. Understanding such evaporation-induced self-assembly (EISA) processes is of interest for both fundamental and technological reasons. Here, we use spatially resolved 2D grazing incidence X-ray scattering in combination with optical interferometry during steady-state dipcoating of surfactant-templated silica thin-films to structurally and compositionally characterize the EISA process. We report the evolution of a hexagonal (p6 mm) thin-film mesophase from a homogeneous precursor solution and its further structural development during drying and calcination. Monte Carlo simulations of water/ethanol/surfactant bulk phase behavior are used to investigate the role of ethanol in the self-assembly process, and we propose a mechanism to explain the observed dilation in unit cell dimensions during solvent evaporation.