ETHENE AND PROPENE COPOLYMERS CONTAINING SILSESQUIOXANE SIDE-GROUPS

The novel monovinyl-functional silsesquioxane cage ecenyl)-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 monov inyl-functional spherosiloxane was obtained from the octahydridosilses quioxane (HSiO3/2)(8) via hydrosilation viith dibrominated decadiene, followed by reaction of the nonreacted SiH groups with ethene, debromi nation, and chromatographic separation. Homopolymerization and copolym erization with ethene and propene was performed using different methyl alumoxane-activated metallocene catalysts. Depending on catalyst struc ture comonomer incorporation between 17 and 25 wt 8 was achieved. High molar mass copolymers were obtained containing pendant octasiloxane c ubes. Characterization by C-13, H-1, and Si-29 NMR spectroscopy confir med that the catalyst did not modify the Si-O-Si framework. Incorporat ion up to 25 wt % (1.2 mol %) of the spherosiloxane-based monomer acco unted for a decrease of the melting temperature by 18 K with respect t o polyethene. As demonstrated by means of thermal gravimetric analysis , thermostability under air was improved in the polyethene copolymer i n comparison to polyethene.