Mechanical Properties and Network Structure of Hydrophobic Association Hydrogels Prepared from Octylphenol Polyoxyethylene(7) Acrylate and Sodium Dodecyl Sulfate

Hydrophobic association hydrogels(HA-gels) with high mechanical strength were prepared by free radical micellar copolymerization in aqueous solutions of acrylamide(AM), anion surfactant sodium dodecyl sulfate(SDS) and a small amount of hydrophobic monomer octylphenol polyoxyethylene(7) acrylate(OP-7-AC). We found that the molar ratio of SDS to OP-7-AC has a great effect on the tensile strength and other mechanical property parameters. The best ratio point R' was determined. On the basis of Mooney theory and statistical theory, the critical tensile ratios and critical tensile strengths of the hydrogels were obtained, elastic parameters C₁ and C₂ were calculated via uniaxial tensile equation and structural parameters, such as the effective network chain density and the averaged molecular weight of the chain between cross-linking points of all the hydrogels were evaluated. The results indicate that the variation of mechanical property parameters depends on the number of effective cross-linking points and the match degree of long and short chains.