Effects of low molecular weight compounds with hydroxyl groups on properties of poly(L-lactic acid)

The effects of low molecular weight compounds with hydroxyl groups on the properties Of poly(L-lactic acid) (PLLA) were investigated. The specific interaction between PLLA and 4,4 ' -thiodiphenol (TDP) was investigated by Fourier transform IR spectroscopy. The spectra of the blends suggested that there were interassociated hydrogen bonds between the PLLA chains and TDP molecules. The thermal and dynamic mechanical properties of PLLA/TDP blends were investigated by differential scanning calorimetry and dynamic mechanical thermal analysis, respectively. The results revealed that the thermal and dynamic mechanical properties of PLLA were greatly modified through blending with TDP and that PLLA/TDP blends possessed eutectic phase behavior. The effects of the thermal history on the formation of hydrogen bonds and the thermal and mechanical properties were evaluated. It was found that the properties of the blends were strongly dependent on the thermal history. In addition to TDP, PLLA blends with other low molecular weight hydroxyl compounds, including aromatic and aliphatic compounds, were also characterized. The effects of the chemical structure of the low molecular weight compounds on the properties of PLLA were discussed. (C) 2001 John Wiley & Sons, Inc.