Syntheses of poly(lactic acid)‐poly(ethylene glycol) serial biodegradable polymer materials via direct melt polycondensation and their characterization

Abstract

AbstractDirectly starting from lactic acid (LA) and poly(ethylene glycol) (PEG), biodegradable material polylactic acid‐polyethylene glycol (PLEG) was synthesized via melt copolycondensation. The optimal synthetic conditions, including prepolymerization method, catalyst kinds and quantity, copolymerization temperature and time, LA stereochemical configuration, feed weight ratio mLA/mPEG and Mn of PEG, were all discussed in detail. When D,L‐LA and PEG (Mn = 1000 Da) prepolymerized together as feed weight ratio mD,l‐LA/mPEG = 90/10, 15 h copolycondensation under 165°C and 70 Pa, and 0.5 wt % SnO as catalyst, gave D,L‐PLEG1000 with the highest [η] of 0.40 dL/g, and the corresponding MW was 41,700 Da. Using L‐LA instead of D,L‐LA, 10 h polymerization under 165°C and 70 Pa, and 0.5 wt % SnO as catalyst, gave L‐PLEG1000 with the highest [η] of 0.21 dL/g and MW of 15,600 Da. Serial D,L‐PLEG with different feed weight ratio and Mn of PEG were synthesized via the simple and practical direct melt copolycondensation, and characterized with FTIR, 1H NMR, GPC, DSC, XRD, and contact angle testing. D,L‐PELG not only had higher MW than PDLLA, PLLA and L‐PELG, but also better hydrophilicity than PDLLA. The novel one‐step method could be an alternative route to the synthesis of hydrophilic drug delivery carrier PLEG instead of the traditional two‐step method using lactide as intermediate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 577–587, 2006