Thiol-ene addition of mercaptoalcohols to poly(vinylsiloxanes) under visible light photocatalysis – An approach towards cross-linkable hydrophilic silicones

Abstract

Addition of thiol compounds bearing electron-withdrawing substituents linked to sulphur atom to vinyl-group containing organosiloxane polymers may be achieved without any catalyst or initiator, only on exposure to visible light. This approach allows for preparation of silicone copolymers with desired amount of unsaturated residues and hydrophilic groups. No detrimental side reactions involving vinyl substituents were observed. The copolymers can be easily cross-linked, as it was shown in model experiments carried out with tetrafunctional pentaerythritol tetrakis(3-mercaptopropionate). Specific surface energy of the obtained cross-linked films and their linear precursors is relatively low despite the presence of –OH groups, irrespectively of their amount and the nature of the support. It makes the prepared copolymers interesting materials to be used as silicone inks for stretchable and wearable electronic devices as well as in microfluidics.