ISSN:
0959-8103
Keywords:
poly(DL-lactic acid)
;
poly(L-lactic acid)
;
poly(D-lactic acid)
;
stereocomplex
;
degradation
;
hydrolysis
;
crystallisation
;
morphology
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
Hydrolytic degradation of intrinsically amorphous poly(DL-lactic acid) was re-examined in pH 7.4 isoosmolar phosphate buffer at 37°C. Size-exclusion chromatogarphy, X-ray scattering and differential scanning calorimetry were used to monitor molecular weight and morphology changes up to the ultimate degradation stage. It was found that heterogeneous degradation of poly(DL-lactic acid) yielded a crystalline residual material of low molecular weight. Comparison with a stereocomplex made of equimolar poly(L-lactic acid) and poly(D-lactic acid) showed that the poly(DL-lactic acid) degradation residue was actually an oligomeric stereocomplex. The formation of stereoregular oligomeric enantiomers agreed well with the predominantly isotactic structure of poly(DL-lactic acid) obtained by ring-opening polymerization of DL-lactide and argued in favour of the stereodependence of main chain ester bond cleavage.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pi.1994.210330105
