Characterization and swelling behavior of hydrogels from N-isopropylacrylamide, N,N′-diethylacrylamide, acrylic acid, and its use for drug release

Abstract

Here, a series of semi-interpenetrating polymer network (semi-IPN) hydrogels were synthesized and investigated by combining three materials such as N-isopropylacrylamide (NIPAM), N,N′-diethylacrylamide (DEA), and acrylic acid (AAc). The linear copolymer p(NIPAM-co-AAc) was introduced into DEA solution in the presence of N,N′-methylenebisacrylamide to synthesize p(NIPAM-co-AAc)/pDEA semi-IPN hydrogels using free radical polymerization. Scanning electron microscope images demonstrated the porous morphology of hydrogels with pore sizes in the range of 220–969 µm. The physicochemical properties of polymers were evaluated by various characterization techniques, including gel permeation chromatography, dynamic light scattering, differential scanning calorimetry, rheological measurement, mechanical properties, and swelling behaviors. The results indicated that the introduction of linear copolymers into conventional hydrogels has significantly improved the properties of the hydrogels. Besides, the use of NIPAM has significantly improved the thermal sensitivity of the polymers in this work. Finally, a selected semi-IPN hydrogel was evaluated for its potential for the drug release of paracetamol. The sorption of paracetamol was an exothermic process that obeyed the Freundlich isotherms, with the highest sorption of 119.57 mg/g. The paracetamol release followed the Korsmeyer–Peppas model and was consistent with the Fickian diffusion mechanism.