Synthesis and characterization of a novel functional biodegradable material, poly(lactic acid-co-borneol)

Directly starting from D,L-lactic acid (LA) and L-borneol, novel biodegradable material poly(lactic acid-co-borneol) (PLAB) was synthesized via melt polycondensation. When the molar feed ratio LA/borneol is 64/1, the influences of different conditions including catalyst kinds and its dosage, copolymerization time, and temperature on the synthesis of the polymer are discussed. When the SnO was used as catalyst and the dosage was 0.3 wt% of the prepolymer, the 5 h direct melt polycondensation at 170 degrees C and absolute pressure of 70 Pa after prepolymerization gave the copolymer with the maximum intrinsic viscosity [eta], 1.51 dL g(-1). The structure of copolymer was confirmed by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (H-1-NMR). According to the appropriate synthetic conditions, the copolymers with different molar feed ratios were synthesized and systematically characterized by [eta], gel permeation chromatography (GPC), differential scanning calorimetry, thermogravimetric, and X-ray diffraction (XRD). The GPC results show that the maximum weight average molecular weight (M-w) of PLAB is 11,900, when the molar feed ratio LA/borneol is 64/1. With the increase of the molar feed ratio of borneol, [eta], M-w and its polydispersity index (M-w/M-n) increase gradually. Due to the introduction of borneol into the copolymer, the glass-transition temperature (T-g) decreases gradually with the increasing feed ratio of borneol. The direct melt copolycondensation is a cheap and practical method for the synthesis of borneol modified polylactic acid, a potential solid borneol flavor, polymeric drug, and functional drug carrier.