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Macrocycles 2 . Living macrocyclic polymerization of ε‐caprolactone with 2,2‐dibutyl‐2‐stanna‐1,3‐dioxepane as initiator
Author(s) -
Kricheldorf Hans R.,
Eggerstedt Seven
Publication year - 1998
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/(sici)1521-3935(19980201)199:2<283::aid-macp283>3.0.co;2-9
Subject(s) - chemistry , polymer chemistry , monomer , copolyester , polymerization , molar mass , transesterification , copolymer , organic chemistry , polymer , polyester , catalysis
ε‐Caprolactone was polymerized in bulk at 80°C with 2,2‐dibutyl‐2‐stanna‐1,3‐dioxepane (DSDOP) as initiator. The reaction time was varied for monomer/initiator molar ratios of 20, 100 and 500. A rapid and complete conversion of the monomer and only slight transesterification or back‐biting degradation were found after longer reaction times. However, significant acceleration of these side reactions was observed at 180°C. Regardless of the M/I ratios and of the reaction time the polydispersities were nearly constant. Number average molecular weights (M̄ n 's) as obtained from GPC measurements are larger than the values obtained from end‐group analyses by 15–25% and increase with increasing molar ratio M/I (at 100% conversion). The living character of the SnO “end‐groups” was demonstrated by acylation with 4‐nitrobenzoyl chloride and by the synthesis of a macrocyclic block copolyester containing β‐ D , L ‐butyrolactone.