A Non-ionic Thermophilic Hydrogel with Positive Thermosensitivity in Water and Electrolyte Solution

The first example of a chemically crosslinked synthetic non-ionic hydrogel showing reversible positive swelling behavior in pure water as well as electrolyte solution is highlighted. Homopolymeric hydrogels are synthesized from N-acryloylglycinamide with N,N′-methylenbis(acrylamide) as a chemical crosslinker via free radical polymerization in dimethyl sulfoxide (DMSO). The swelling-ratio dependency of the hydrogels upon temperature as well as on the amounts of crosslinker from 1 to 4.8 mol% is studied. With 1 mol% crosslinker, the hydrogel is able to take up over three times water of its weight at 37 °C in pure water and phosphate-buffered saline. All the samples show almost 100% of reversibility for at least 6 d up to 37 °C irrespective of the amount of the crosslinker, making them promising candidates for biomedical applications. The sample with a higher amount of crosslinker, i.e., 4.8 mol% is even stable for over 6 d at 70 °C.