Correlation of hydrolytic degradation with structure for copolyesters produced from glycolic and adipic acids.
Copolyesters based on glycolic acid (G) combined with adipic acid (A) and ethylene glycol (E) were synthesized in different percentage of molar ratios (A: 100-50% and G: 100%) and their hydrolytic degradation was studied and correlated with their structures. According to the DSC, the production of polyesters leads to the formation of copolyesters and not to mixtures of homopolyesters. The crystallites in the copolyesters mainly consist of continuous sequences of ethylene adipate structural units. The hydrolytic degradation of the polyesters was followed by their weight loss during hydrolysis and by the FTIR spectra of the initial polyesters compared with that of the degraded polyesters at equilibrium. The region between 1142 and 800 cm(-1) can be utilized to evaluate the extent of degradation of polyesters after their hydrolysis. The absorption bands at 1142, 1077 and 850 cm(-1) due to the amorphous region decrease after hydrolysis, whereas those at 972, 901 and 806 cm(-1) due to the crystalline region increase. The experimental data of the hydrolytic degradation were fitted with exponential rise to maximum type functions using two-parameter model, which describes very well mainly the initial part of the degradation, and four-parameter model (containing two exponential terms), which is appropriate for fitting the hydrolytic degradation on the entire time period (including the equilibrium). Furthermore, the kinetics of the hydrolytic degradation of the polyesters for the initial time period based on both models results to similar values of the rate constant, k. The synthesized copolyesters of glycolic acid combined with adipic acid and ethylene glycol are soluble in many common organic solvents opposite to PGA, leading to modified biodegradable polyesters and therefore they can be easily processed.
Simitzis
J
J
School of Chemical Engineering, Department III Materials Science and Engineering, National Technical University of Athens, Athens, Greece. simj@chemeng.ntua.gr
Triantou
D
D
Soulis
S
S
Triantou
K
K
Simitzis
Ch
Ch
Zoumpoulakis
L
L
D020341:Absorbable Implants; D000272:Adipates / Q000737:chemistry / Q000493:pharmacokinetics*; D001672:Biocompatible Materials / Q000737:chemistry; D001673:Biodegradation, Environmental; D001711:Biotransformation; D004337:Drug Carriers / Q000138:chemical synthesis / Q000737:chemistry / Q000493:pharmacokinetics; D006016:Glycolates / Q000737:chemistry / Q000493:pharmacokinetics*; D006868:Hydrolysis; D008422:Materials Testing / Q000379:methods; D015233:Models, Statistical; D015394:Molecular Structure; D011091:Polyesters / Q000138:chemical synthesis / Q000737:chemistry / Q000493:pharmacokinetics*; D017550:Spectroscopy, Fourier Transform Infrared; D013329:Structure-Activity Relationship; D013499:Surface Properties; D013696:Temperature
D000272:Adipates; D001672:Biocompatible Materials; D004337:Drug Carriers; D006016:Glycolates; D011091:Polyesters; C031149:glycolic acid