DIRECT EVIDENCE OF CROSS-LINKS IN A BUTADIENE-DIMETHYLDIVINYLSILANE COPOLYMER BY METATHESIS DEGRADATION

A butadiene-dimethyldivinylsilane copolymer with 5.6 mol% dimethyldivinylsilane (MVS) was obtained with n-butyl-lithium as initiator. It was degraded by cross metathesis with (E)-4-octene or (E)-3-hexene in the presence of the catalyst WCl6/Sn(CH3)4. The reaction mixtures were investigated by means of gas chromatography/mass spectrometry coupling. The degradation products contained 1,4-linked butadiene (1,4B), 1,2-linked butadiene (1,2B) and tetrafunctionally polymerized MVS. The sequences 1,4B-MVS-1,4B, 1,4B-MVS-1,2B-1,4B and 1,4B-1,2B-MVS-1,22B-1,4B were found in the crosslinks. In metathesis degradation, cyclohexene rings were formed from the sequence 1,4B-MVS-1,4B and cyclopentene rings from the sequence MVS-1,2B-1,4B. The mass spectra of some characteristic products are discussed.