Synthesis of poly(D,L-lactic acid) modified by triethanolamine by direct melt copolycondensation and its characterization



Using D,L-lactic acid (LA) and multifunctional group compound triethanolamine (TEA) as starting materials, a novel biodegradable material poly(D,L-lactic acid-triethanolamine) [P(LA-TEA)] was directly synthesized by simpler and practical melt polycondensation. The appropriate synthetic condition was discussed in detail. When the molar feed ratio LA/TEA was 30/1, the optimal synthesis conditions were as follows: a prepolymerization time of 12 h; 0.5 weight percent (wt %) SnO catalyst; and melt copolycondensation for 8 h at 160°C, which gave a novel star-shaped poly(D,L-lactic acid) (PDLLA) modified by TEA with the maximum intrinsic viscosity [η] 0.93 dL g−1. The copolymer P(LA-TEA) as a different molar feed ratio was characterized by [η], Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H-NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). Increasing the molar feed ratio of LA/TEA, Tg and Mw increased. However, all copolymers were amorphous, and their Tg (12.2°C–32.5°C) were lower than that of homopolymer PDLLA. The biggest Mw was 9400 Da, which made the biodegradable polymer be potentially used as drug delivery carrier, tissue engineering material, and green finishing agent in textile industry. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011