Preparation of environmental resistance and anti-swelling hydrogel through solvent displacement for monitoring human health and movement in amphibious environment

Abstract

Recently, the utilization of anti-swelling hydrogels in extreme environment garners increasing attention. However, most hydrogels fail to satisfy harsh requirements of maintaining favorable performance in extreme condition due to its porous network structure and high hydrophilicity. Therefore, it is important to design hydrogel with anti-swelling ratio and underwater environmental resistance. Herein, P(AMPS/HEMA/EG) hydrogel was prepared by solvent displacement, which was polymerized by 2-acrylamide-2-methylpropanesulfonic acid (AMPS), hydroxyethyl methacrylate (HEMA) as monomer, N, N’-methylene-bis-acrylamide (MBAA) as crosslinking agent and ammonium persulfate (APS) as initiator in ethylene glycol (EG), followed by solvent displacement. Hydrophilic PAMPS chains and hydrophobic PHEMA chains endowed P(AMPS/HEMA/EG) hydrogel with anti-swelling behavior by reaching hydrophilic-hydrophobic segments balance. The sulfonic acid group formed multiple hydrogen bonds with hydroxyl groups, resulting in P(AMPS/HEMA/EG) hydrogels exhibiting great mechanical properties. The free negatively charged sulfonic acid group and the ionized positively charged hydrogen ions endowed the P(AMPS/HEMA/EG) hydrogel with conductivity. Based on this strategy, the hydrogel showed anti-swelling ratio and underwater environment resistance. After 30 days soaking in 60 ℃ deionized water, 0.2 M NaCl and NaNO₂ solution and acetone, the swelling ratio were −44.05 %, 0.44 %, −12.12 % and –23.96 %, respectively. Furthermore, the mechanical property stability of hydrogel was enhanced by the strong hydrogen bond after solvent displacement. The stress of hydrogel increased by 119.62 % after immersing in 0.6 M NaCl solution for 15 days. Based on the above properties, the hydrogels could be employed as flexible sensor in amphibious environment. Therefore, this environmental resistance hydrogels possessed profound impact on wide range applications.