POLYMERIZED MONOMOLECULAR FILMS - MICROSCOPIC STRUCTURE, VISCOSITY, AND PHOTOPOLYMERIZATION KINETICS

The photopolymerization of monolayers prepared at the gas-water interf ace with two styrene functionalized surfactants is studied and peculia r features of the film structures are described. When these films are irradiated with UV light, at constant surface pressure, their areas de crease monotonically as a function of the irradiation time. Phase sepa ration and microscopic morphological changes induced by the polymeriza tion process are investigated by using fluorescence microscopy and sca nning force microscopy. During irradiation, domains of higher density and thickness are formed. The shapes and sizes of these domains, which are evidently the polymeric phase, depend on surface pressure and irr adiation time. The film viscosities are measured before and after poly merization and are related to the irradiation time and the mean sizes of the polymeric domains. Film surface area measurements and image ana lysis are used to obtain the area occupied by a bound monomer in the p olymeric phase. A kinetics model of the photopolymerization, taking in to account the peculiar features of the almost two-dimensional system, is used to fit the experimental results of the surface area variation with the irradiation time.