Polydimethylsiloxanes with vinyl ether end-groups—I. Synthesis and properties as polymerizable wetting agents

Abstract

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CH 2] 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., 1H- and 13C-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.