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Polylactones, 52. Tin Carboxylates as Initiators of ε ‐Caprolactone
Author(s) -
Kricheldorf Hans R.,
Stricker Andrea,
Langanke Dennis
Publication year - 2001
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 - 10.1002/1521-3935(20011001)202:15<2963::aid-macp2963>3.0.co;2-c
Subject(s) - chemistry , polymerization , monomer , polymer chemistry , carboxylate , caprolactone , reactivity (psychology) , tin , bulk polymerization , polyester , polymer , organic chemistry , radical polymerization , medicine , alternative medicine , pathology
Eleven different tin carboxylates were used as initiators of the ring‐opening polymerization of ε ‐caprolactone. All polymerizations were conducted with 2 M solutions in chlorobenzene at 80°C and time/conversion curves were determined up to 96–99% conversion. The following structure‐reactivity relationships were found. Noncyclic initiators, such as Bu 2 Sn(acetate) 2 or Bu 2 Sn(benzoate) 2 are more reactive than cyclic initiators such as Bu 2 Sn succinate and Bu 2 Sn phthalate, respectively. Electron withdrawing substituents enhance the reactivity. Bu 2 Sn(acetate) 2 is more reactive than Bu 3 Sn acetate and Sn(II) bis(2‐ethylhexanoate) is more reactive than Bu 2 Sn(2‐ethyl‐hexanoate) 2 . Traces of moisture to play the role of efficient co‐initiators. This conclusion is supported by the following observations. The degrees of polymerization ( DP ) largely exceed the monomer/initiator (M/I) ratios. Furthermore, the DP s increase with the purity of ε ‐CL suggesting that the monomer itself carries traces of moisture. The co‐initiation with water and the incorporation of a few acyl endgroups were confirmed by MALDI‐TOF mass spectroscopy. CH 2 OH endgroups were also found in all polyesters by 1 H NMR spectroscopy, whereas only traces of acyl endgroups were detectable. Tetrabutyldistannoxane bisacetate is far more reactive than Bu 2 Sn bisacetate. Addition of an alcohol to a tin carboxylate allows a control of the molecular weight, and, as previously reported by several research groups, accelerates the entire polymerization process.