title: Thermal degradation of poly(3-hydroxyalkanoates): preparation of well-defined oligomers.
abstract: The thermal degradation of the biodegradable bacterial polyesters poly(3-hydroxybutyrate), PHB, poly(3-hydroxyvalerate), PHV, and poly(3-hydroxybutyrate-co-3-hydroxyvalerate), 0-21 mol % of hydroxyvalerate, was studied. At moderately low temperatures (170-200 degrees C), the main product is a well-defined oligomer, especially a 500-10,000 g/mol macromolecule, which contains one unsaturated end group, predominantly a trans-alkenyl end group, as well as a carboxylic end group. The process was studied regarding the effect of the copolymer composition and reaction time at 190 degrees C. During the first few hours of reaction, the thermal degradation of PHB and PHV followed a kinetic model of random scission, but eventually auto-acceleration of the pyrolysis was detected, probably due to the influence of the crotonate end groups of the oligomers formed. Ten-time scale-up experiments on a Brabender instrument were successfully undertaken.
authors.affiliation: Department of Chemistry, McGill University, 3420 University Street, Montreal, Quebec, H3A 2A7, Canada.
authors.forename: Sophie
authors.initials: S
authors.lastname: Nguyen
authors.forename: Ga-er
authors.initials: GE
authors.lastname: Yu
authors.forename: Robert H
authors.initials: RH
authors.lastname: Marchessault
mesh_terms: D002850:Chromatography, Gel; D006358:Hot Temperature / Q000009:adverse effects*; D006885:Hydroxybutyrates / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D011091:Polyesters / Q000378:metabolism*; D016339:Spectrometry, Mass, Fast Atom Bombardment; D000094122:Polyhydroxybutyrates
chemical_list: D006885:Hydroxybutyrates; D011091:Polyesters; C003182:poly-beta-hydroxybutyrate; D000094122:Polyhydroxybutyrates