ACYCLIC DIENE METATHESIS (ADMET) COPOLYMERIZATION - CONTROLLED DIENE INSERTION IN POLY[(HEXAMETHYLTRISILOXANEDIYL)BUTENYLENE]

The single repeat unit insertion of 4,4'-di-trans-1-propenylbiphenyl (4) into poly[(1,1,3,3,5,5-hexamethyl-1,3,5-trisiloxane-1,5-diyl)butenylene] (3) via acyclic diene metathesis (ADMET) copolymerization catalyzed by [(CF3)2CH3CO]2(N-2,6-C6H3-i-Pr2)W=CHC(CH3)2Ph (1) is presented. The cross metathesis condensation of an unsaturated polymer with an aromatic diene monomer allowed for random and isolated insertion of the biphenylene linkages throughout the polycarbosiloxane. In addition to cometathesis reactions, the copolymer 5 also continued to condense ethylene and grow in molecular weight. The copolymer was characterized by H-1 NMR and quantitative C-13 NMR spectroscopy and UV spectrophotometry. Molecular weights were determined by quantitative C-13 NMR and GPC. The copolymer 5 underwent uninitiated cross-linking under an inert atmosphere and degraded after prolonged exposure to air under ambient conditions. Thermal stabilities of the polymer starting material, copolymer, and degraded products are compared.