Emulsion copolymerization ofD,L-lactide and glycolide in supercritical carbon dioxide

Autor: David D. Hile, Michael V. Pishko
Rok vydání: 2001
Předmět:
Zdroj: Journal of Polymer Science Part A: Polymer Chemistry. 39:562-570
ISSN: 1099-0518
0887-624X
Popis: Biodegradable polyesters were synthesized via an emulsion polymerization in supercritical carbon dioxide (SC-CO 2 ). Copolymers of lactide and glycolide were synthesized in SC-CO 2 with stannous octoate as the ring-opening catalyst and a fluorocarbon polymer surfactant as an emulsifying agent. The conversion of lactide and glycolide was monitored with respect to the reaction time and temperature with 1 H NMR spectroscopy. The conversion of glycolide surpassed 99% within 72 h for an SC-CO 2 phase maintained at 200 bar and 70 °C. Under the same conditions, lactide conversion reached 65% after 72 h of polymerization. Unpolymerized monomer was removed after the reaction by extraction with an SC-CO 2 mobile phase. The molecular weights of all the copolymers were measured by gel permeation chromatography. Weight-average molecular weights (M w ) ranged between 2500 and 30,200 g/mol and polydispersity indices ranged from 1.4 to 2.3 for polymerization times of 6 and 48 h, respectively. Although the molecular weight increased significantly during the first 48 h of reaction, there was no significant difference in the M w for polymerization times of 48 and 72 h. Emulsion polymerization within the benign solvent SC-CO 2 demonstrated improved conversion and molecular weight versus polymers synthesized without surfactant. The emulsion polymerization of lactide and glycolide copolymers in SC-CO 2 is proposed as a novel production technique for high-purity, biodegradable lvmers.
Databáze: OpenAIRE
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