Spontaneous ring-opening copolymerization of 1,1,2,2-tetramethyl-1,2-disilacyclobutane with styrene

1,1,2,2-Tetramethyl-1,2-disilacyclobutane (TMDSCB), obtained by alkali meta l vapor dehalogenation of 1,2-bis(chlorodimethylsilyl)ethane, undergoes roo m-temperature spontaneous ring-opening copolymerization with styrene (St) a nd results in a rubbery copolymer (M-w = 1.6 x 10(5), M-w/M-n = 4.4). In co ntrast to a thermoplastic homopolymer of TMDSCB (m.p. 110 degrees C) that i s obtained by the same procedure in the absence of styrene, the copolymer e xhibits two-phase behavior (T-g = - 37 degrees C, m.p. 106 degrees C), with the heat of merting being considerably lower in the case of the copolymer (cf. 49.0 and 4.8 J g(-1)). Spectral and analytical data are consistent wit h a copolymer structure, [(Me2SiCH2CH2SiMe2)(k) (CH2CHPh)(l)](n), where k = 3, l = 1 (36 %), and k = 6, l = 2 (64 %).