Polymerization of cyclotrisiloxanes by organolithium compounds and P2-Et base

✍ Scribed by Aart Molenberg; Martin Möller

• Book ID: 102483681
• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 458 KB
• Volume: 198
• Category: Article
• ISSN: 1022-1352
• DOI: 10.1002/macp.1997.021980304

✦ Synopsis

Abstract

The use of the phosphazene base P~2~‐Et^(a)^ as a promoter for the anionic polymerization of hexamethylcyclotrisiloxane (D~3~^Me^) or hexaethylcyclotrisiloxane (D~3~^Et^) initiated by an organolithium compound leads to well‐defined polysiloxanes. At low conversion (< ca. 9%) the polymerization of D~3~^Me^ behaves like a living polymerization, however, polymers with a narrow molecular weight distribution (M̄~w~/M̄~n~ < 1.1) are obtained up to much higher conversions (ca. 70%). Kinetic data and NMR spectroscopy revealed the existence of a dynamic equilibrium between complexed and uncomplexed lithium silanolates. Below ambient temperature several different types of aggregates were indicated. The occurrence of an acceleration was observed after ca. 9% conversion.