Preparation of acrylamide-urea composite hydrogels based on deep eutectic solvents and their self-healing and pressure-sensitive properties

This study utilized choline chloride (ChCl) as the hydrogen bond acceptor, while acrylamide (AM) and urea functioned as hydrogen bond donors. A P(AM-Urea) composite hydrogel was successfully synthesized using a ternary deep eutectic solvent (DES) system and in-situ polymerization. The effects of varying AM/Urea molar ratios on the swelling behavior, mechanical properties, self-healing abilities, and pressure sensitivity of the hydrogels were systematically analyzed. The results indicated that an increase in AM content significantly enhanced both the swelling capacity and mechanical strength of the hydrogels. The SP5 sample (AM/Urea molar ratio 1.5:0.5) exhibited optimal performance, achieving a tensile strength of 4.86 MPa and a compressive strength of 5.6 MPa, which were 7.5 and 4.55 times higher, respectively, than those of the SP1 sample. Self-healing experiments revealed that the SP3 hydrogel, with an AM/Urea molar ratio of 1:1, achieved a healing efficiency of 80% within 20 h. Additionally, in pressure sensitivity tests, the SP1 hydrogel with lower AM content exhibited superior piezoelectric performance, with a capacitance change rate of 59.98%, which was 3.2 times greater than that of the SP5 sample. The P(AM-Urea) composite hydrogel developed in this study exhibits exceptional swelling, mechanical strength, self-healing capabilities, and pressure-responsive characteristics, highlighting its potential applications in sensing, biomedicine, and environmental engineering.