The forces between layers of a cationic polymerizable surfactant, cetyl p-vinylbenzyl dimethyl ammonium chloride (CVDAC), adsorbed onto muscovite mica have been measured with a surface force technique. The forces were measured both before and after partial UV polymerization of the adsorbed layers, and the stability of adsorbed bilayers after dilution of the adsorption solution was studied for these two cases. Due to their large headgroup, CVDAC molecules do not pack efficiently into monolayers and bilayers. This can be observed by, for instance, the lower surface potential of adsorbed bilayers and the lower pull-off force from monolayer contact, compared to what is found for simpler surfactants like CTAB. It was also found that surface aggregates build up on top of the bilayer, due to the partly hydrophobic headgroup. When the bilayer structure, including the surface aggregates, is polymerized, it is stabilized both with respect to mechanical forces and with respect to dilution of the surrounding solution. (C) 1994 Academic Press, Inc.