AFM Observation of a Mica Surface Treated with Silane Coupling Agent Having a Mercapto Group

The topography of mica surface after treatment with silane coupling agent having a mercapto group was studied using an atomic force microscope. The cleaved mica plate was used as a model inorganic surface. The effect of treatment condition on the topography of the mica surface was investigated. Agglomerates consisting of self-condensed silane molecules were observed on the surface. However, their amount and size were smaller than those for silanes having other organo-functional groups such as amino, methacryloxy and vinyl groups. Aqueous and water/2-propanol mixture solutions gave a smoother surface as compared with a 2-propanol solution. There was no significant influence discernable from di- and trialkoxy structures. The aqueous solution of silane coupling agent having a mercapto group showed an acidic pH. This was the reason why the smoother silane-treated layer was formed by the silane with the mercapto group than by those with other organic functional groups, because the silanol group generated by hydrolysis is stable in an acidic pH.