FILM FORMATION AND CRACK DEVELOPMENT IN PLASMA-POLYMERIZED HEXAMETHYLDISILOXANE

Plasma polymer thin coatings can be used in a variety of applications that require thin ultrasmooth, defect-free homogeneous films. In this study both film formation and crack development are described and rela ted to the structure of the plasma polymer. The growth of a plasma pol ymer film reproduces the topography of the porous (polysulfone) PSf su pport and the time needed for complete coverage depends on the rate of deposition which is a function of the plasma power and monomer flow r ate. The plasma polymerized hexamethyldisiloxane, PPHMDSO, film on a P Sf porous support is under compressive internal stress causing the mem brane to bend convexly with respect to the film. Despite these stresse s, the composite membrane (film/support) did not crack when freely imm ersed in water and alcohols. Cracks developed in the mechanically cons trained PPHMDSO composite membrane on exposure to alcohols. Films with more organic character showed high adhesion among the plasma polymer nodules and between the plasma polymer and the PSf substrate, resultin g in substrate tearing and cracking straight through the plasma polyme r layer.