COMPATIBILIZATION BY SULFONATE IONOMERS IN POLYBLENDS WITH THERMOTROPIC LIQUID-CRYSTALLINE POLYMERS

It is shown by differential scanning calorimetry (DSC) measurements th at Lightly sulfonated polystyrene (SPS) is partially miscible with pol ysulfone (PSF), polycarbonate (PC), polyetherimide (PEI), and a thermo tropic liquid crystalline polymer (LCP). Fourier transform infrared an alysis confirms that the miscibility of SPS and PSF, and of SPS and PC , comes from the ion-dipole interaction between the sulfonate groups o f SPS and the polar groups of PSF and PC, respectively. After the addi tion of SPS to LCP/PSF, LCP/PC, and LCP/PEI blends, this specific inte raction leads to the compatibilization of SPS in these blends, which i s revealed by inward glass transition temperature shifts of component polymers in DSC and dynamic mechanical analysis thermograms and by a m uch finer dispersion of the minor LCP phase in these matrix polymers. The utilization of SPS as the compatibilizer results in a stronger int erfacial adhesion between LCP and matrix phases and improves the mecha nical performances of LCP/PSF, LCP/PC, and LCP/PEI blends as well. Com pared with ternary LCP/PSF, LCP/PC, and LCP/PEI blends with polystyren e as an inert third component, the ternary LCP/SPS/PSF, LCP/SPS/PC, an d LCP/SPS/PEI blends have significantly enhanced tensile strengths and moduli, with acceptable processabilities at the same time. (C) 1998 J ohn Wiley & Sons, Inc.