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Polymerization of cyclotrisiloxanes by organolithium compounds and P 2 ‐Et base
Author(s) -
Molenberg Aart,
Möller Martin
Publication year - 1997
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.1997.021980304
Subject(s) - phosphazene , polymerization , polymer chemistry , chemistry , anionic addition polymerization , molar mass distribution , polymer , base (topology) , living polymerization , ring opening polymerization , living anionic polymerization , radical polymerization , organic chemistry , mathematical analysis , mathematics
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.
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