Synthesis of Bio-Based Poly(lactic acid-co-10-hydroxy decanoate) Copolymers with High Thermal Stability and Ductility

Novel bio-based aliphatic copolyesters, poly(lactic acid-co-10-hydroxy decanoate) (P(LA-co-HDA), PLH), were successfully synthesized from lactic acid (LA) and 10-hydroxycapric acid (HDA) by a thermal polycondensation process, in the presence of p-toluenesulfonic acid (p-TSA) and SnCl2·2H2O as co-catalyst. The copolymer structure was characterized by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1H NMR). The weight average molecular weights (Mw) of PLH, from gel permeation chromatography (GPC) measurements, were controlled from 18,500 to 37,900 by changing the molar ratios of LA and HDA. Thermogravimetric analysis (TGA) results showed that PLH had excellent thermal stability, and the decomposition temperature at the maximum rate was above 280 °C. The glass transition temperature (Tg) and melting temperature (Tm) of PLH decreased continuously with increasing the HDA composition by differential scanning calorimetry (DSC) measurements. PLH showed high ductility, and the breaking elongation increased significantly by the increment of the HDA composition. Moreover, the PLH copolymer could degrade in buffer solution. The cell adhesion results showed that PLH had good biocompatibility with NIH/3T3 cells. The bio-based PLH copolymers have potential applications as thermoplastics, elastomers or impact modifiers in the biomedical, industrial and agricultural fields. OPEN ACCESS Polymers 2015, 7 469