Effect of surfactant on the swelling and mechanical behavior of NIPAM-based terpolymer

In the present study, the effects of PEG-PPG-PEG surfactant on the thermoresponsive properties, swelling behavior and mechanical strength of NIPAM-based terpolymers have been elaborated. NIPAM-based thermoresponsive terpolymers were synthesized by free radical polymerization in the absence and presence of surfactant PEG-PPG-PEG. The synthesized hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), swelling kinetics, mechanical properties and scanning electron microscopy. FTIR confirmed the presence of monomer and absence of pore-forming agent PEG-PPG-PEG. TGA revealed the reaction zones during their degradation for which activation energy was calculated using Coats–Redfern method. The surface morphology of conventional hydrogels was found to be less porous than PEG-PPG-PEG modified hydrogels. PEG-PPG-PEG modified hydrogels showed higher rate of swelling and deswelling but less mechanical stability compared to conventional hydrogels. Also, PEG-PPG-PEG modified hydrogels have increased gel characteristic constant (k) and average diffusion coefficient in comparison with the conventional hydrogels. Separation efficiency of the modified hydrogels in bovine serum albumin (BSA) protein solution was found to be decreased which may be attributed to adsorption of BSA molecule.