The effects of pH on the structure of polystyrene-nano manganese dioxide composites

Abstract

Loading nano manganese dioxide (NMO) on the surface of polymers change the pH of point zero charge (pHPZC) of the dioxide. In this work, a polystyrene-NMO composite was prepared and the effects of pH from 1 to 14 on its structural and morphological properties were investigated. Moving-window, and perturbation-correlation moving-window two-dimensional correlation spectroscopies were used to analyze the pH-dependent Fourier transform infrared spectra of the composite. The auto correlation showed a peak value around pH=4 corresponding to the pHPZC of the composite, and another peak value around pH=9, which was assigned to change in the NMO structures. X-ray diffraction patterns and scanning electron microscopy further confirmed the changes at both pH=4 and pH=9 that were accompanied by a change in the morphology and crystalline structures of the composite. Moving-window and perturbation-correlation moving-window two-dimensional correlation spectroscopies are powerful tools in finding overlapped, weak, and hidden peaks along the spectral direction and could be used to locate the pHPZC of solid materials.