End group analysis accounts for the low molecular weight observed in the 1,3-divinyltetramethyldisiloxane-Pt complex catalyzed hydrosilylation copolymerization of alpha,omega-dienes and 1,3-dihydridotetramethyldisiloxane

The 1,3-divinyltetramethyldisiloxane-Pt complex (Karstedt catalyst) facilit ates copolymerization of alpha,omega-dienes, such as 1,7-octadiene or 1,5-h exadiene, with 1,3-dihydridotetramethyldisiloxane. Spectroscopic analysis o f the copolymers indicates the presence dimethylsiloxy and either 2-octenyl or 2-hexenyl end groups. Apparently, the catalyst not only facilitates the hydrosilylation reaction of 1,3dihydridotetramethyldisiloxane with termina l C-C double bonds but also catalyzes the isomerization of terminal alkenes to internal alkenes, which are not reactive.