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, T_g and M_w increased. However, all copolymers were amorphous, and their T_g (12.2°C–32.5°C) were lower than that of homopolymer PDLLA. The biggest M_w 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