MODIFICATION OF SURFACE-PROPERTIES OF UV-CURED FILMS IN THE PRESENCE OF LONG-CHAIN ACRYLIC-MONOMERS

Acrylic films have been prepared by photopolymerization of mixtures of an epox H-(CH2)(n)-O-CO-CH = CH2 with n ranging from 4 to 18. The resins were cast on a glass slide and cured in an inert atmosphere; their surface properties were investigated by advancing and receding contact angles and surface tension measurements according to the Zisman method. The pure resin film showed the same surface properties on both sides, that exposed to the atmosphere and that in contact with the substrate. Addition of the acrylic monomers caused an asymmetric distribution of them on the two sides of the film, depending on the alkylic chain length and on the acrylic monomer concentration. The asymmetry of the film was confirmed by XPS analysis that pointed out a significant enrichment of the apolar monomer on the air side. The surface properties were correlated to the monomer polarity (ruled by its hydrocarbon chain length). The contact angle hysteresis provided insight into the heterogeneity and the roughness of the polymeric surface. (C) 1995 Academic Press, Inc.