Abstract
The influence of ethylene glycol methacrylate (EGMA) to the hydration and transition behaviors of thermo-responsive interpenetrating polymeric network (IPN) hydrogels containing sodium alginate, N-isopropylacrylamide (NIPAAm), and EGMA were investigated. The molar ratios of NIPAAm and EGMA were varied from 20:0 to 19.5:0.5 and 18.5:1.5 in the thermo-responsive alginate-Ca2+/P(NIPAAm-co-EGMA) IPN hydrogels. Due to the more hydrophilicity and high flexibility of EGMA, the IPN hydrogels exhibited higher lower critical solution temperature (LCST) and lower glass transition temperature (Tg) when the ratio of EGMA increases. The swelling/deswelling kinetics of the IPN hydrogels could be controlled by adjusting the NIPAAm/EGMA molar ratio. A faster water uptake rate and a slower water loss rate could be realized by increase the amount of EGMA in the IPN hydrogel (the shrinking rate constant was decreased from 0.01207 to 0.01195 and 0.01055 with the changing of NIPAAm/EGMA ratio from 20:0, 19.5:0.5 to 18.5:1.5). By using 2-Isopropylthioxanthone (ITX) as a photo initiator, the obtained alginate-Ca2+/P(NIPAAm-co-EGMA360) IPN hydrogels were successfully immobilized on cotton fabrics. The surface and cross section of the hydrogel were probed by scanning electron microscopy (SEM). They all exhibited a porous structure, and the pore size was increased with the amount of EGMA. Moreover, the LCST values of the fabric-grafted hydrogels were close to those of the pure IPN hydrogels. Their thermal sensitivity remained unchanged. The cotton fabrics grafted with hydrogel turned out to be much softer with the continuous increase of EGMA amount. Therefore, compared with alginate-Ca2+/PNIPAAm hydrogel, alginate-Ca2+/P(NIPAAm-co-EGMA360) hydrogel is a more promising candidate for wound dressing in the field of biomedical textile.
Highlights
Hydrogels are three-dimensional polymeric networks with hydrophilic groups that can absorb from 10–20% up to hundreds of times their dry weight in water [1,2]
The influence of ethylene glycol methacrylate (EGMA ) to the hydration and and transition behaviors of a thermo-responsive interpenetrating network360 (IPN) hydrogels series transition behaviors of a thermo-responsive interpenetrating network (IPN) hydrogels series consisting consisting of sodium alginate, N-isopropylacrylamide (NIPAAm) and ethylene glycol methacrylate of sodium alginate, N-isopropylacrylamide (NIPAAm) and ethylene glycol methacrylate (EGMA360 )
differential scanning calorimetry (DSC) and temperature stimulus-responsive equilibrium swelling ratio results indicated indicated that hydrogels with increased EGMA360 composition ratio exhibit higher lower critical solution temperature (LCST)
Summary
Hydrogels are three-dimensional polymeric networks with hydrophilic groups that can absorb from 10–20% up to hundreds of times their dry weight in water [1,2]. Temperature is the easiest triggering signal for phase transition in hydrogels because it is the most available biomedical index, which can be adjusted and controlled. Among these thermal-responsive hydrogels, poly(N-isopropylacrylamide) (PNIPAAm) gel is a typical thermosensitive hydrogel that exhibits an abrupt volume transition in response to change of temperature around 33 ◦ C. Upon heating up to its LCST, PNIPAAm becomes hydrophobic as a result of the separation of polymer chains from water Because of this unique property, plenty of investigations about the PNIPAAm hydrogels are focused on the phase transition, the effects influencing the transition behavior, and variation of its transition behavior [10]. One of the most critical shortcomings of traditional PNIPAAm hydrogels is their slow response rate to external temperature change due to the initial formation of a dense skin layer, which delays the diffusion of interior water molecules during the collapse process at temperatures above the LCST [15]
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