Synthesis of poly(lactide-co-glycolide) containing high glycolide contents by ring-opening polymerization as well as their structural characterizations, thermal properties, morphologies, and hydrophilicity

摘要

Random copolymers, poly(l-lactide-r-glycolide) are synthesized by one-pot ring-opening polymerization of l-lactide and glycolide in the presence of stannous octoate and 1-dodecanol. Block copolymers, poly(l-lactide-b-glycolide) are synthesized by ring-opening polymerization of l-lactide to generate poly(l-lactide) first and then further ring-opening polymerization of glycolide in the presence of poly(l-lactide) and stannous octoate. The composition ratio of l-lactide and glycolide is determined by the integration of the corresponding signals from H-1 NMR spectra, which is consistent with the feeding ratio. Very few hetero-sequences can be observed for block copolymers due to well-defined microstructures. The block copolymers are more thermally stable than that of the random copolymers. The degree of crystallinity of the bock copolymers is relatively high compared to that of the random copolymers. The image of the block copolymers determined by field-emission scanning electron microscopy (FESEM) shows partial aggregate domains containing spherical particles with an average diameter of around 200 nm, which is very different from that of the random copolymers. Block copolymers are more hydrophilic than that of the random copolymers due to the ordered structure and amphiphilic behavior of the block series.