G. Toskas, M. Moreau, M. Masure
May 31, 2001
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0
Influential Citations
20
Citations
Journal
Macromolecules
Abstract
Cationic polymerization of hexamethylcyclotrisiloxane (D3) initiated by HCl and antimony pentachloride (SbCl5) may give a high polymer (HP) with controlled molecular weight in high yield, and only small amounts of cyclic compounds. Theoretical Mn's were formerly obtained with D3 using as initiator either triflic acid or a combination of a silyltriflate activated by triflic acid. However, considerable amounts of cyclic compounds were also formed, e.g. 50 wt % D6/HP and up to 20% macrocycles. D6 was mainly formed by a reaction involving transitory oxonium ions and macrocycles by cyclization of silanol esters. Using two other initiating systems, the formation of D6 and macrocycles was significantly decreased and was sometimes suppressed. The polymerization was rapid with SbCl5 and HCl at −10 °C, producing about 90% high polymer of Mn ≥ 105, 10−12% small cycles (only 3% D6) and no macrocycles. The Mn's agreed with an initiation by HCl and a propagation involving the silanol end groups, which explains the abse...