CATIONIC PHOTOCROSSLINKABLE POLYDIMETHYLSILOXANE .3. SYNTHESIS AND PHOTO-CROSS-LINKING OF POLYDIMETHYLSILOXANE BEARING OXETANE GROUPS

From 3-hydroxymethyl-3-methyl oxetane, we synthesized three oxetane mo nomers with allylic, diethoxysilane or triethoxysilane functions. Thes e monomers allowed us to prepare different polydimethylsiloxanes beari ng oxetane soups by two routes. One is hydrosilylation of allylic mono mer on hydrogeno polydimethylsiloxane, with different percentages of S i-H bonds. The second route is a condensation of alpha,omega-dihydroxy polydimethylsiloxane with di and tri ethoxysilane monomers. By using a photocalorimeter, we studied the kinetic of cationic photopolymeriza tion of a polydimethylsiloxane bearing 7.4% oxetane functions. Influen ce of temperature in the range 35 to 125 degrees C showed a maximum co nversion for 80 degrees C due to an increase in transfer and terminati on reactions.