Synthesis, melt molding and hydrolytic degradation of poly(L-lactide-co-L-methylglycolide) and its composites with carbonated apatiteстатья
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Дата последнего поиска статьи во внешних источниках: 10 июля 2024 г.
Аннотация:Poly(lactic-co-glycolic acid)s (PLGAs) hold considerable significance for their biomedical applications. Biodegradation and mechanical properties of PLGAs and PLGA-based composites are strongly influenced by lactate/glycolate (L/G) ratio in copolymers, molecular weight characteristics and microstructure of PLGAs. The common approach to PLGAs is based on ring-opening copolymerization of lactides and glycolide, the products of which contain long (L)n and (G)n segments. An efficient but expensive approach to PLGAs with given L-G sequences is a segmer assembly polymerization that is hardly applicable for the synthesis of high-MW PLGAs. In the present work, for the first time we synthesized lactate-enriched PLGAs using ring-opening copolymerization of L-lactide (L-LA) with L-methylglycolide (L-MeGL) in 85:15 and 70:30 molar ratios, resulting in L-PLMG 85/15 and L-PLMG
70/30 copolymers. L-PLGA 85/15 with the same L/G ratio as in PLMG 70/30 was synthesized by ring-opening copolymerization of L-LA with glycolide as a sample for a comparison. According to 1H and 13C NMR data and [α]D measurements, L-MeGL-based PLGAs had a unique microstructure, e.g. macromolecules of L-PLMG 85/15 consisted of Ln sequences with single G insertions. Composites of PLLA and three samples of PLGAs with platelike carbonated apatite (pCAp) containing 25 and 50 wt.% of the filler were prepared. Rectangular specimens from (co)polymers and (co)polymer composites were obtained by injection molding and studied. Due to the absence of highly reactive (G)n fragments, L-PLMG 85/15 and PLMG 70/30-based materials demonstrated higher thermal and hydrolytic stability, mechanical testing showed that L-MeGL-based copolymers provide better maintaining of the bending strength in comparison with L-PLGA 85/15 matrix.