Highly thermally resistant UV-curable poly(siloxane)s bearing bulky substituents

Novel thermally stable polysiloxanes with bulky side chain tris(trimethylsilyl)hexyl and reactive glycidoxypropyl substituents were synthesized via hydrosilylation route and were further cross-linked in the presence of diaryliodonium salt upon exposure to UV light. The cross-linking was necessary to stabilize the shape of the linear tris(trimethylsilyl)hexyl group modified siloxanes which potentially can be used as membranes for fluid separation at high temperatures. Formation of oligoether cross-linking chains was proved by solid state C-13 NMR analyses. Six copolymers of diverse molecular architecture were made based on methylsiloxane and methylsiloxane-co-dimethylsiloxane backbones. The ratio between [tris(trimethylsilyl)hexyl](methyl)-siloxane and (glycidoxypropyl)(methyl)siloxane monomeric units in polymer chain, ranging from 0.5 to 5.4, was found to be an important factor affecting the thermal properties of cross-linked films, as shown by TGA.