Ring-Opening Olefin Metathesis Polymerisation (ROMP) as a Potential Cross-Linking Mechanism for Siloxane Polymers

Reported here are some results of rapid Ring Opening Metathesis Polymerization (ROMP) of norbornene-functional oligomeric siloxanes using a Ru-based catalytic system. The in situ formation of the active metal carbene catalyst by addition of a diazo compound to norbornene-functional siloxane containing the catalytic system, [(p-cymene)RuCl₂]₂/PCy₃ allowed fast but controlled polymerization of the norbornene functionalities. Thus, in a solventless system, polymerization of a norbornene-functional siloxane, e.g., 1,1,1,2,3,3,3-heptamethyl-2-norbornen-5-yltrisiloxane, at 60°C with low catalyst levels (2 to 200 ppm) led to a colourless monolithic gel in less than 30 seconds. Besides being an efficient cross-linking technology, ROMP of suitable precursors may also be a source of novel silicone-organic materials.