Self-healing Mechanism and Mechanical Behavior of Hydrophobic Association Hydrogels with High Mechanical Strength

Hydrophobic association hydrogels (HA-gels) were prepared through micellar copolymerizationof acrylamide (AM) and a small amount of octyl phenol polyethoxy ether acrylate (OP-4-AC) in an aqueous solution containing sodium dodecyl sulfate (SDS) at 50°C. The resulting HA-gels exhibited excellent mechanical properties and transparency. However, the most striking properties were that HA-gels possessed the capability of self-healing. The mechanical properties of HA-gels were investigated by uniaxial stretching. The results showed that the mechanical properties of HA-gels could be varied greatly by changing OP-4-AC content in the range of OP-4-AC used. On the basis of the rubber elastic theory and using uniaxial stretching data, the effective network chain density and the average distance between the cross-linking points were calculated for HA-gels. For tensile measurements of altering crosshead speed, the modulus of HA-gels increased sharply with increasing crosshead speed. The stress-relaxation behavior of HA-gels consisted of two stages. Similar to rubbery, HA-gels exhibited obvious thermoelastic behavior and also showed a good rubberlike elastic property.