TBD-catalyzed anionic ring-opening polymerization of hexamethylcyclotrisiloxane: a new route for controlled synthesis of PDMS

Abstract

Controlled anionic ring opening polymerization of hexamethylcyclotrisiloxane (D3) was optimized for commercial and easy to use organic catalyst 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) using various types of initiators. Alcohols and silanols were compared for the synthesis of monofunctional and telechelic PDMS. Polymerizations were monitored by 1H NMR spectroscopy, MALDI-TOF mass spectroscopy and SEC in order to compare the effects of the initiator structure and of the catalyst concentration. TBD was shown to control the AROP of D3 when using silanols as initiator, thus affording well-defined PDMS structures. When alcohols were used as initiators, the polymerization proceeded with lower level of control due to slower initiation. These differences in initiation rates likely originate from the differences in pKa between silanols and alcohols.