Effect of bisphenol A on the miscibility, phase morphology, and specific interaction in immiscible biodegradable poly(ε-caprolactone)/poly(L- lactide) blends

We have investigated the enhancement in miscibility, upon addition of bisphenol A (BPA) of immiscible binary biodegradable blends of poly(epsilon-caprolactone) (PCL) and poly(L-lactide) (PLLA). That BPA is miscible with both PCL and PLLA was proven by the single value of T-g observed by differential scanning calorimetry (DSC) analyses over the entire range of compositions. At various compositions and temperatures, Fourier transform infrared spectroscopy confirmed that intermolecular hydrogen bonding existed between the hydroxyl group of BPA and the carbonyl groups of PCL and PLLA. The addition of BPA enhances the miscibility of the immiscible PCL/PLLA binary blend and transforms it into a miscible blend at room temperature when a sufficient quantity of the BPA is present. In addition, optical microscopy (OM) measurements of the phase morphologies of ternary BPA/PCL/ PLLA blends at different temperatures indicated an upper critical solution temperature (UCST) phase diagram, since the Delta K effect became smaller at higher temperature (200 degrees C) than at room temperature. An analysis of infrared spectra recorded at different temperatures correlated well with the OM analyses. (c) 2006 Wiley Periodicals, Inc.