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Characterization of a homologous series of d,l-lactic acid oligomers; a mechanistic study on the degradation kinetics in vitro

Paper ID Volume ID Publish Year Pages File Format Full-Text
12780 816 2003 10 PDF Available
Title
Characterization of a homologous series of d,l-lactic acid oligomers; a mechanistic study on the degradation kinetics in vitro
Abstract

A series of low molecular weight polymers of d,l-lactic acid has been synthesized. The oligomers were characterized with respect to molecular weight, glass transition temperature and solubility. The number average molecular weight of the oligomers ranged from 290 to 1320 Da. Oligomers with an were soluble in buffer at pH 7.4 but insoluble in water and acidic medium.Kinetic studies were performed at pH 1.5, 4.5 and 7.4 using an accelerated in vitro monomer release test. The hydrolytic rate was dependent on molecular weight of oligomer, temperature and pH of the media, with the lowest rate found around pH 4.5. The activation energy was dependent on molecular weight and ranged from 47 to 67 kJ mol−1. Random ester cleavage was identified as mechanism of hydrolysis in basic media whereas in acidic media chain-end cleavage (“unzipping”) was the mode of action.

Keywords
d,l-lactic acid; Degradation mechanism; Hydrolysis rate constant; Activation energy
First Page Preview
Characterization of a homologous series of d,l-lactic acid oligomers; a mechanistic study on the degradation kinetics in vitro
Publisher
Database: Elsevier - ScienceDirect
Journal: Biomaterials - Volume 24, Issue 21, September 2003, Pages 3835–3844
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering