AFM study of forces in and structures of nematic liquid crystal interfaceson silanated glass

We have studied interfacial forces in MBBA, 5CB, 8CB and 12CB liquid crysta ls on DMOAP silanated glass substrates using a temperature controlled AFM i n the force spectroscopy mode. In the bulk isotropic phase all these interf aces are clearly divided into two regions. The first molecular layer, which is absorbed to the glass surface, is smectic-like and shows submicron hole s. this layer covers approximately 70% of the surface and is in all cases s table far beyond the clearing point. It is followed by a partially ordered region, which is different for different materials. We observe pre-nematic ordering in 5CB, pre-smectic ordering in 8CB and well developed layer-by-la yer ordering in 12CB.