title: Structural characterization of a lipase-catalyzed copolymerization of epsilon-caprolactone and D,L-lactide.
abstract: The copolymerization of epsilon-caprolactone (epsilon-CL) and d,l-lactide catalyzed by Candida antarctica lipase B was studied. Copolymerizations with different epsilon-CL-to-lactide ratios were carried out, and the product was monitored and characterized by MALDI-TOF MS, GPC, and (1)H NMR. The polymerization of epsilon-CL, which is normally promoted by C. antarctica lipase B, is initially slowed by the presence of lactide. During this stage, lactide is consumed more rapidly than epsilon-CL, and the incorporation occurs dimer-wise with regard to the lactic acid (LA) units. As the reaction proceeds, the relative amount of CL units in the copolymer increases. The nonrandom copolymer structure disappears with time, probably due to a lipase-catalyzed transesterification reaction. In the copolymerizations with a low content of lactide, macrocycles of poly(epsilon-caprolactone) and copolymers having up to two LA units in the ring were detected.
authors.affiliation: Swedish Pulp and Paper Research Institute, Box 5604, SE-114 86 Stockholm, Sweden.
authors.forename: Jessica
authors.initials: J
authors.lastname: Wahlberg
authors.forename: Per Valdemar
authors.initials: PV
authors.lastname: Persson
authors.forename: Tove
authors.initials: T
authors.lastname: Olsson
authors.forename: Erik
authors.initials: E
authors.lastname: Hedenström
authors.forename: Tommy
authors.initials: T
authors.lastname: Iversen
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry / Q000378:metabolism; D002175:Candida / Q000201:enzymology; D002208:Caproates / Q000737:chemistry* / Q000378:metabolism*; D002384:Catalysis; D007783:Lactones / Q000737:chemistry* / Q000378:metabolism*; D008049:Lipase / Q000378:metabolism*; D015394:Molecular Structure; D011091:Polyesters / Q000737:chemistry* / Q000378:metabolism*; D011108:Polymers / Q000737:chemistry* / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D001672:Biocompatible Materials; D002208:Caproates; D007783:Lactones; D011091:Polyesters; D011108:Polymers; C033616:poly(lactide); C121056:caprolactone; D008049:Lipase