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

Abstract

The controlled anionic ring-opening polymerization of hexamethylcyclotrisiloxane (D₃) was optimized for a commercial and easy-to-use organic catalyst, 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), employing 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 to compare the effects of the initiator structure and catalyst concentration. TBD was shown to control the AROP of D₃ when using silanols as the initiator, thus affording well-defined PDMS structures. When alcohols were used as initiators, the polymerization proceeded with a lower level of control due to slower initiation. These differences in initiation rates likely originated from the differences in pK_a between silanols and alcohols.