Linked Life Data

15244468

Source:http://linkedlifedata.com/resource/pubmed/id/15244468

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4
pubmed:dateCreated
2004-7-12
pubmed:abstractText
Effects of chain-end structure and residual metal compounds on thermal degradation of poly(epsilon-caprolactone) (PCL) were investigated by means of thermogravimetric and pyrolysis-gas chromatograph mass spectrometric analyses. Four types of PCL samples with different chain-end structures (alpha-carboxylic acid-omega-hydroxyl-PCL, alpha-dodecyl ester-omega-hydroxyl-PCL, alpha-carboxylic acid-omega-acetyl-PCL, and alpha-dodecyl ester-omega-acetyl-PCL) were prepared by ring-opening polymerization of epsilon-caprolactone in the presence of zinc-based catalyst and by subsequent acetylation reaction of polymers with acetic anhydride. PCL samples with different zinc contents were obtained by washing with acetic acid in chloroform solution of polymer. Thermal degradation behaviors of these PCL samples with different chain-end structures were examined under both isothermal and nonisothermal conditions. From both the isothermal and nonisothermal experiments, the thermal degradation of PCL samples containing high amounts of residual zinc compounds from synthesis process revealed the selective unzipping depolymerization step below 300 degrees C producing epsilon-caprolactone exclusively. In contrast, zinc-free PCL samples were stable at temperatures below 300 degrees C, and the thermal degradation occurred only at temperatures above 300 degrees C regardless of the chain-end structure. From (1)H NMR analysis of the residual molecules after isothermal degradation of zinc-free PCL, it was confirmed that the omega-chain-end of residual molecules was 5-hexenoic acid unit. However, the cyclic monomer and oligomers were detected as the volatile products of zinc-free PCL samples. These results suggest that the dominant reaction of thermal degradation for PCL above 300 degrees C is a competition between the random chain scission via cis elimination reaction and the cyclic rupture via intramolecular transesterification of PCL molecules.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:issn
1525-7797
pubmed:author
pubmed:issnType
Print
pubmed:volume
5
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1480-8
pubmed:dateRevised
2008-8-14
pubmed:meshHeading
pubmed:articleTitle
Effects of residual zinc compounds and chain-end structure on thermal degradation of poly(epsilon-caprolactone).
pubmed:affiliation
Polymer Chemistry Laboratory, RIKEN Institute, Hirosawa, Wako-shi, Saitama 351-0198, Japan. habe@postman.riken.go.jp
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't