Synthesis of thermo-responsive poly(N-vinylcaprolactam): RSM-based parameters optimization

Abstract

Currently, there is an urge to change poly (N-isopropylacrylamide) (PNIPAM) (the most popular thermoresponsive polymer) to poly (N-vinylcaprolactam) (PNVCL) (a more suitable and smart polymer). At the physiological temperature range (32–34 °C), PNVCL precipitates from aqueous solutions. The lower toxicity of PNVCL makes it more suitable for use compared to PNIPAM. The aim of this study is to optimize the synthesis parameters of PNVCL. The effective parameters considered during polymer conversion are temperature, time, monomer concentration, and the initiator concentration; response surface methodology was used to study the effect of these parameters. The optimized parameters were analyzed using analysis of variance (ANOVA) and the optimized values for the maximum conversion (100%) were found at the maximum time and temperature of 180 min and 80 °C, respectively. From the ANOVA results, time and temperature were found to significantly affect the conversion rate, followed by the initiator concentration and the monomer concentration. New predictive correlations were developed using ANOVA analysis approach to estimate the polymer conversion. The coefficient (R2) value of the developed correlation was 0.9638, while the p value of the developed model was less than 0.001. Therefore, the developed model was significant in the estimation of the value of the polymer conversion and the existing correlations were suitable for polymer conversion. Conclusively, the optimization method developed in this study improved the polymer conversion rate.