SYNTHESIS AND APPLICATIONS OF PHOTOCROSSLINKABLE POLYDIMETHYL SILOXANES .3. SYNTHESIS OF POLYSILOXANES WITH PERFLUORINATED AND ACRYLATED URETHANE LINKED PENDANT GROUPS

The synthesis of photocrosslinkable polysiloxanes containing perfluorinated pendant groups and that of acrylated groups linked by methanes moieties was performed. The synthesis was carried out by copolycondensation of alpha, omega-dihydroxypolydimethylsiloxane and dichloro silanes bearing fluorinated and acetoxy groups. The acrylation was conducted by an omega-isocyanato-acrylate on the polysiloxane polyol prepared by acetolysis of the previous copolysiloxanes. The chain lengths are checked by addition of a monochlorosilane in order to obtain (M) over bar(n) values of about 10(4) mol/g. The influence of the fluorine content on the properties was investigated. Actually the critical superficial tension decreased from 25.5 to 21.0 and the T-g of the copolymer decreased to - 120 degrees C when a C8F17 group was introduced. The use of these copolymers by u.v. curing was evaluated on sheets of aluminium, of PET and paper. The adhesion on these substrates are very good and release properties were studied, showing that incorporation of C8F17 pendant group gave the best results.