Optimization of the glass transition temperature of polyvinyl pyrrolidone/polyacrylamide blend films using response surface methodology

Abstract In this study, we aimed at synthesizing polymeric materials consisting of polyvinyl pyrrolidone (PVP) enhanced polyacrylamide (PAM) blend films and optimizing the glass transition temperature ( T g ) of the synthesized polymeric blends. The PAM and PVP polymers were blended through solution casting techniques by varying PAM (0.3–1.2 g) and PVP (0.3–1 g) concentrations in parallel. The response surface methodology (RSM) experimental design, a mathematical and statistical method, was used to design the experiments, model the process, and determine the optimum concentrations of the blended films having the lowest T g value. The polymeric blends were characterized using differential scanning calorimetry (DSC) to investigate their phase transition temperatures such as their T g . Moreover, the polymeric blends with the lowest T g values were characterized using Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analyzer (TGA), and UV–Vis spectroscopy to investigate the interactions existing between the parental polymers, the thermal stability, and the optical properties such as energy band gap of the parental polymers and optimized blended films respectively. It was found that T g of the blended films was strongly dependent on the concentrations of the parental polymers, and PAM polymer exhibited a more pronounced effect on the T g of the blended films. The T g of the synthesized films declined when the parental polymers were blended at higher concentrations. The energy band gap and the thermal stability of the optimized blended films were lower than that of the parental polymers (i.e., 4.90 eV and 210°C). The DTG curve of the optimized blended films exhibited a maximum weight loss at 467°C. The RSM statistical analysis revealed a high regression coefficient ( R 2 ) of 0.970 for the T g of the blended films, showing the experimental values analyzed are in good agreement with the developed model. Numerical optimization results showed that an optimum concentration of the blended films yielded the lowest T g value of 83.63°C, which is close to the predicted T g of 82.32°C, was achieved with 1.2 g of PAM and 1 g of PVP. The higher T g value of the optimized blended films indicates that the polymer blends formed are highly brittle at room temperature when available in a dry state.