Study of Structural, Optical and Acoustical Properties of Sodium Sulfate Incorporated Polyvinyl Pyrrolidone (PVP) Composite

Abstract

The structural, optical and acoustical properties of a polymer composite of sodium sulfate (Na2SO4) doped polyvinyl pyrrolidone (PVP) were studied. The simple chemical route method was utilized for the preparation of the polymer composite by varying the concentration of Na ions in the PVP. The pure 3% PVP solution was mixed with five different concentrations of Na2SO4 solutions in the ratio of 80:20. X-ray diffraction (XRD) spectra of PVP/Na2SO4 (1.0% of Na2SO4 in 3.0% of PVP) confirmed the crystalline nature of the PVP/Na2SO4 polymer composite. The identification of several chemical functional groups contained in the PVP/Na2SO4 was demonstrated by Fourier transform infrared (FTIR) spectroscopy. The FTIR showed the excellent interaction between the polymer (PVP) and the dopant Na2SO4. Optical studies were performed by utilizing a UV-visible absorbance spectrophotometer. The UV-VIS spectroscopy results indicated that absorption increased in an asymmetric manner and the absorption peak showed a red shift with increasing Na ions concentration in the host PVP. The optical band gaps (direct and indirect) were found to decrease with increase in Na ions concentration in the polymer due to increase in the density of localized states in the band-gap. The activation and Urbach energies were evaluated from the conductivity measurements and the absorption coefficient, respectively. Several acoustical parameters, viz. ultrasonic velocity, density, viscosity, adiabatic compressibility, intermolecular free length, acoustic impedance, and surface tension, were also computed. The ultrasonic velocity, acoustic impedance, density, viscosity, and surface tension of the polymer solutions were found to increase while the adiabatic compressibility and intermolecular free length decreased with the addition of increasing amounts of Na ions in PVP.