Effect of isothermal annealing on the hydrolytic degradation rate of poly(lactide-co-glycolide) (PLGA).
Isothermal crystallization through annealing at 115 degrees C was conducted to increase the degree of crystallinity of poly (lactide-co-glycolide) (PLGA). The maximum increase in the degree of crystallinity (approximately 21%) was achieved after 60 min of annealing. The crystal size/perfection was observed to increase with annealing time. The annealed PLGA films were then hydrolytically degraded in phosphate buffered saline solution of pH 7.4 at 37 degrees C for up to 150 days. Minimal mass loss was observed throughout the time investigated, suggesting that the samples were still in the first phase of degradation. The increase in the degree of crystallinity of the PLGA samples annealed at 15 and 30 min was found to retard their overall rate of hydrolytic degradation, when compared to those samples with higher initial crystallinity (annealed for 45 and 60 min) that had faster degradation rates. The increased degradation rate at higher crystallinity was associated with the loss of amorphous material and the formation of voids during annealing, which decreases the glass transition temperature and increases the average water uptake in the samples annealed for longer times. Therefore, the increase in degree of crystallinity is found to retard hydrolytic degradation but only to a certain extent, beyond which the formation of voids through annealing increases the rate of hydrolytic degradation.
Loo
Say Chye Joachim
SC
School of Materials Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Singapore.
Ooi
Chui Ping
CP
Wee
Siew Hong Elyna
SH
Boey
Yin Chiang Freddy
YC
D001672:Biocompatible Materials / Q000737:chemistry*; D003460:Crystallization; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D019344:Lactic Acid / Q000737:chemistry* / Q000378:metabolism; D008567:Membranes, Artificial; D008956:Models, Chemical; D011091:Polyesters / Q000737:chemistry; D011100:Polyglycolic Acid / Q000737:chemistry* / Q000378:metabolism; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers / Q000737:chemistry* / Q000378:metabolism; D013696:Temperature; D013997:Time Factors; D014961:X-Ray Diffraction
D001672:Biocompatible Materials; D008567:Membranes, Artificial; D011091:Polyesters; D011108:Polymers; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid