Synthesis, characterization and protein separation efficiency of N-isopropylacrylamide-co-N-tertiary butylacrylamide-co-acrylamide-based hydrogels

Abstract

In the present study, hydrogels were prepared by free radical polymerization in water–dioxane mixture with fixed molar ratio (25 mol%) of N-isopropylacrylamide (NIPAM) and varying remaining molar concentrations of N-tert-butylacrylamide (NTBA) and acrylamide (AAm). The structure of the resultant hydrogels was studied by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) techniques. The thermal properties of the hydrogels were analyzed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) methods. DSC thermograms were used for the quantitative determination of free, interfacial and bound water contents. The result showed that the free and interfacial water contents increased with increase in the hydrophilic AAm content, and the bound water content increased with hydrophobic NTBA content in the hydrogels. Swelling behavior of the hydrogels was evaluated at different temperatures. The percentage swelling and diffusion kinetic parameters (network structure constant, type of diffusion and diffusion constant) were calculated for all samples. The diffusion was found to be Fickian type for copolymer having equimolar concentrations of NTBA and AAm and non-Fickian type for others. Diffusion coefficients of the hydrogels were found to be increased with increasing temperature. In addition, poly(NIPAM-co-NTBA-co-AAm) hydrogels were used in concentration separation process for BSA solution. The result showed that the copolymer with equimolar NTBA and AAm contents has high separation efficiency with good thermoresponsive behavior among all copolymers.