POLYDIMETHYLSILOXANES WITH VINYL ETHER END-GROUPS .1. SYNTHESIS AND PROPERTIES AS POLYMERIZABLE WETTING AGENTS

Novel polydimethylsiloxanes (PDMS) bearing vinyl ethers end-groups were prepared by coupling the Si-H functions of telechelic PDMS with triethyleneglycol divinyl ether (DVE-3) or with 1,4-bis(vinyloxymethyl)cyclohexane (CHVE). The conditions of this Pt-catalysed hydrosilylation reaction were adjusted so as to obtain quantitative conversion at moderate temperature and for reduced reaction times. The influence of the excess of the initial vinyl ether concentration [O-CH=CH2]0/[Si-H]0 on the molecular weight of the obtained functional polymers was studied by gel permeation chromatography (GPC). A 10-fold excess of the divinyl ether reactant was shown to limit the possibility of polymer-polymer coupling and afforded modified PDMS exhibiting DP(n) and molecular weight distributions similar to that of the starting PDMS. The polymers were made free of contaminants by precipitation in methanol and were characterized by i.r., H-1- and C-13-NMR spectroscopy. Vinyl ether functional PDMS were tested as additives in representative cationically curable photosensitive compositions. The influence of the silicone wetting agent on the properties of the u.v.-cured coatings was examined by comparative tests. They were shown to induce a wetting effect comparable to conventional fluorinated surfactants and present in addition reactive end-groups allowing the surfactant to take place in the network.