Ethene and propene copolymers containing silsesquioxane side groups

The novel monovinyl-functional silsesquioxane cage 1-(9-decenyl)-3,5,7,9,11,13,15-heptaethylpentacyclo[9.5. 1.1(3,9).1(5,15).1(7,13)]octasiloxane has been prepared and copolymerized with ethene and propene. The monovinyl-functional spherosiloxane was obtained from the octahydridosilsesquioxane (HSiO3/2)(8) via hydrosilation viith dibrominated decadiene, followed by reaction of the nonreacted SiH groups with ethene, debromination, and chromatographic separation. Homopolymerization and copolymerization with ethene and propene was performed using different methylalumoxane-activated metallocene catalysts. Depending on catalyst structure comonomer incorporation between 17 and 25 wt 8 was achieved. High molar mass copolymers were obtained containing pendant octasiloxane cubes. Characterization by C-13, H-1, and Si-29 NMR spectroscopy confirmed that the catalyst did not modify the Si-O-Si framework. Incorporation up to 25 wt % (1.2 mol %) of the spherosiloxane-based monomer accounted for a decrease of the melting temperature by 18 K with respect to polyethene. As demonstrated by means of thermal gravimetric analysis, thermostability under air was improved in the polyethene copolymer in comparison to polyethene.