SYNTHESIS AND CHARACTERIZATION OF MONOFUNCTIONAL POLYDIMETHYLSILOXANES WITH A NARROW MOLECULAR-WEIGHT DISTRIBUTION

Polydimethylsiloxanes (PDMSs) with a narrow molecular weight distribut ion and fitted at one chain end with a hydrogenodimethylsilyl or a dim ethylvinylsilyl function were prepared by the anionic ring-opening rea ction of hexamethylcyclotrisiloxane in a 50 vol% benzene-tetrahydrofur an solution, followed by endcapping with chlorodimethylsilane or chlor odimethylvinylsilane. The experimental conditions were chosen on the b asis of preliminary experiments in order to minimize the contribution of reshuffling reactions and it was checked that the possible formatio n of difunctional species was negligible. The functionalization was qu antitative. The functional polymers were characterized by i.r. spectro scopy and by s.e.c. alpha-Hydrogenodimethylsilyl and alpha-dimethylvin ylsilyl PDMS were prepared in the molecular mass range between 2500 an d 40 000 g mol(-1).