INFLUENCE OF MOLECULAR-STRUCTURE ON THE DEGRADATION MECHANISM OF DEGRADABLE POLYMERS - IN-VITRO DEGRADATION OF POLY(TRIMETHYLENE CARBONATE), POLY(TRIMETHYLENE CARBONATE-CO-CAPROLACTONE), AND POLY(ADIPIC ANHYDRIDE)
Ac. Albertsson et M. Eklund, INFLUENCE OF MOLECULAR-STRUCTURE ON THE DEGRADATION MECHANISM OF DEGRADABLE POLYMERS - IN-VITRO DEGRADATION OF POLY(TRIMETHYLENE CARBONATE), POLY(TRIMETHYLENE CARBONATE-CO-CAPROLACTONE), AND POLY(ADIPIC ANHYDRIDE), Journal of applied polymer science, 57(1), 1995, pp. 87-103
Relationships between molecular structure and the degradation mechanis
m of degradable polymers are of special interest for temporary medical
applications. The in vitro degradation study of three aliphatic polym
ers-poly(trimethylene carbonate) (PTMC), poly(trimethylene carbonate-c
o-caprolactone) (PTMC-PCL), and poly(adipic anhydride) (PAA)-revealed
that these polymers exhibit degradation times from several years (PTMC
) to 1 day (PAA). PTMC degraded unexpectedly slow, accompanied by very
small changes in weight loss, molecular weight (SEC), and in morpholo
gy (DSC, SEM). The degradation was independent of initial molecular we
ight, ionic strength of the water solution, temperature, and shaking m
otions. The copolymer PTMC-PCL showed a higher degradation rate compar
ed to PTMC, with preferential degradation of amorphous parts leading t
o an increase in % crystallinity. The surprisingly rapid degradation o
f PAA showed characteristics typical for a surface-like eroding system
in contrast to PTMC and PTMC-PCL. The degradation products correspond
ed to the repeating unit of the polymers. The hydrolysis rate increase
s in the order carbonate, ester, anhydride, and by combining different
molecular structures we achieve specific degradation behavior. A chan
ge in hydrolysis rate of the labile bond is predicted by altering the
electronegativity of groups near the carbonyl-oxygen region. (C) 1995
John Wiley and Sons, Inc.