Preparation and Properties of Polyglycolide , Poly(L-lactide) and Poly(L-lactide-co-glycolide)

Polyglycolide (PGA), poly (L-lactide) (PLLA) and poly (L-lactide-co-glycolide) (PLGA) were prepared by bulk ring-opening polymerization at high temperature and high vacuum using stannous octoate as catalyst and 1,4-butanediol as initiator. The chemical structures of the polymers were characterized by infrared spectroscopy (IR) and H nuclear magnetic resonance (H-1-NMR), and their properties were studied by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA), X-ray diffraction (XRD) and rheometry. The results-of GPC showed that PLGA and PLLA had high molecular weight and narrow molecular weight distribution. The results of TGA showed that PGA, PLLA and PLGA had high thermal stability and the decomposition temperature increased slowly with increasing units of PGA in PLGA. PGA directly obtained with bulk polymerization was not dissolved in various organic solvents, while the solubility of PGA in hexafluoroisopropanol (HFIP) increased obviously after recrystallization from dimethyl sulfoxide (DMSO). PGA and PLLA had higher crystallinity while PLGA was amorphous, PGA crystallized from DMSO had lower crystallinity. The melts of PGA,PLLA and PLGA were shear-thinning fluids, while PGA and PLLA had higher storage modulus and PLGA had higher loss modulus. Amorphous PLGA was much more easily purified and processed than PGA and PLLA having higher crystallinity, thus PLGA was more suitable to be used as biodegradable material.