Poly[(N-isopropylacrylamide)-co-(itaconic acid)] hydrogels with poly(ethylene glycol)

Abstract

The aim of the work reported here was to investigate temperature- and pH-sensitive hydrogels of N-isopropylacrylamide (NIPAM) and itaconic acid (IA) and their semi-interpenetrating polymer networks (semi-IPNs) with varying contents of poly(ethylene glycol) (PEG). The stimuli responsiveness, swelling behaviour and mechanical properties of the hydrogels and semi-IPNs were studied in order to investigate the effect of various amounts of PEG. Pulsed-gradient spin-echo NMR experiments were carried out to investigate the diffusion process. The pH sensitivity increased with an increasing amount of PEG in the semi-IPNs, while the overall rate of water uptake was diffusion-controlled (n lt 0.5). For certain PEG contents (5 and 10 wt%), the semi-IPNs exhibited better mechanical properties than the poly(NIPAM-co-IA) copolymer. The calculated values of the self-diffusion coefficients of water indicated facilitated diffusion of water through the system with increased amounts of PEG, while the self-diffusion coefficients of a model compound, metoprolol tartrate, showed no significant dependence on the amount of PEG. According to the results obtained and compared to results reported in the literature, the investigated semi-IPNs may have potential applications in the controlled release of macromolecular active agents such as proteins and peptides.