Preparation and properties of physically and chemically cross-linked hybrid hydrophobic association hydrogels with good mechanical strength

To correct the defects of hydrophobic association hydrogels (HA-gels), new physically and chemically cross-linked hybrid hydrophobic association hydrogels (hybrid HA-gels) were prepared by radical copolymerization of acrylamide (AM), octylphenol polyoxyethylene (n) acrylate (OPnAC, n stands for the number of ethoxy group, and is 10 and 21) and N,N′-methylenebisacrylamide (MBA). On the basis of the statistical molecular theory of rubber elastic, the Mooney-Rivlin model and using the tensile true stress (σ true) tested at room temperature, the number of network strands per unit volume (υ 0) and the number-average molar mass of a network strand (M c) were evaluated for hybrid HA-gels. For the hydrogels, the effect of the content of MBA and OP10AC on their tensile mechanical properties was studied by using υ 0 and M c; also, the effect of the compositions and temperature on their swelling behavior in distilled water was discussed in detail. In addition, hybrid HA-gels including a small quantity of MBA possessed the capabilities of secondary self-healing and remolding. In contrast with HA-gels prepared by the same compositions besides MBA, hybrid HA-gels showed good mechanical strength and long-term thermal stability in distilled water in the range of 25 to 80 °C. Furthermore, hybrid HA-gels also avoided the self-deswelling behavior of HA-gels. The results show that the application fields of HA-gels will be greatly broadened after introducing a chemical cross-linking network.