Miscibility Studies of Polymer Blends Containing a Phytochemical

Miscibility studies of amorphous poly(amide)/poly(vinyl pyrrolidone) (PA/PVP) blends containing a crystalline phytochemical belonging to 'xanthone' family have been carried out using differential scanning calorimetry (DSC), Fourier transformed infrared spectroscopy (FTIR) and polarized optical microscopy (POM). The binary blends of PA/PVP prepared from dimethylsulfoxide (DMSO) solutions were found to be completely miscible showing a systematic movement of a single glass transition temperature over the entire composition range. The FTIR study indicated the occurrence of hydrogen bonding interactions between PA and PVP, which may be responsible for complete miscibility of the PA/PVP pair. Moreover, hydrogen bonding promotes miscibility in binary blends of PA/xanthone and PVP/xanthone. However, the addition of xanthone to PA/PVP blends has resulted in liquid-liquid phase separation at low concentrations of xanthone. With increasing xanthone concentration, crystallization occurs leading to phase segregation between isotropic liquid phase (PA/PVP) and crystal phase of xanthone. On the basis of DSC and POM, a ternary morphology phase diagram of the PA/PVP/xanthone blends was established, which exhibited various coexistence regions such as isotropic, liquid + liquid, liquid + crystal, liquid + liquid + crystal, and solid crystal regions.