Poly(L-lactide), 8 - High-temperature hydrolysis of poly(L-lactide) films with different crystallinities and crystalline thicknesses in phosphate-buffered solution

Citation
H. Tsuji et al., Poly(L-lactide), 8 - High-temperature hydrolysis of poly(L-lactide) films with different crystallinities and crystalline thicknesses in phosphate-buffered solution, MACRO MAT E, 286(7), 2001, pp. 398-406
Citations number
43
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
MACROMOLECULAR MATERIALS AND ENGINEERING
ISSN journal
1438-7492 → ACNP
Volume
286
Issue
7
Year of publication
2001
Pages
398 - 406
Database
ISI
SICI code
1438-7492(20010727)286:7<398:P8-HHO>2.0.ZU;2-D
Abstract
Poly(L-lactide) (PLLA) films having different crystallinities (X-c's) and c rystalline thicknesses (L-c's) were prepared by annealing at different temp eratures (T-a's) from the melt and their high-temperature hydrolysis was in vestigated at 97 degreesC in phosphate-buffered solution. The changes in re maining weight, molecular weight distribution, and surface morphology of th e PLLA films during hydrolysis revealed that their hydrolysis at the high t emperature in phosphate-buffered solution proceeds homogeneously along the film cross-section mainly via the bulk erosion mechanism and that the hydro lysis takes place predominantly and randomly at the chains in the amorphous region. The remaining weight was higher for the PLLA films having high ini tial X-c when compared at the same hydrolysis time above 30 h. However, the difference in the hydrolysis rate between the initially amorphous and crys tallized PLLA films at 97 degreesC was smaller than that at 37 degreesC, du e to rapid crystallization of the initially amorphous PLLA film by exposure to crystallizable high temperature in phosphate-buffered solution. The hyd rolysis constant (k) values of the films at 97 degreesC for the period of 0 -8 h, 0.059-0.085 h(-1) (1.4-2.0 d(-1)), were three orders of magnitude hig her than those at 37 degreesC for the period of 0-12 months, 2.2-3.4 x 10(- 3) d(-1). The melting temperature (T-m) and X-c of the PLLA films decreased and increased, respectively, monotonously with hydrolysis time, excluding the initial increase in T-m for the PLLA film prepared at T-a = 100, 120, a nd 140 degreesC in the first 8, 16, and 16 h. respectively. A specific peak that appeared at a low molecular weight around 1 x 10(4) in the GPC spectr a was ascribed to the component of one fold in the crystalline region. The relationship between T-m and L-c was found to be T-m (K) = 467.[1-1.61/L-c (nm)] for the PLLA films hydrolyzed at 97 degreesC for 40 h.