IMPACT OF SURFACTANT ON THE PROPERTIES OF THE HYDROPHOBICALLY ASSOCIATING HYDROGELS

The hydrophobically associating hydrogels, namely HA gels and SHA gels, were prepared by free radical copolymerization of acrylamide (AM) and sodium 9 or 10-acrylamidostearic acid (NaAAS) in pure water and in aqueous solution of sodium dodecyl sulphate (SDS), respectively, without any chemical crosslinkers. The mechanical properties of HA gels and SHA gels were systematic investigated by one-way tensile experiments, and the results confirmed the high toughness of the as-obtained hydrogels. Further more,by adjusting the AM and NaAAS contents, the SHA gels could exhibit ultrahigh toughness compared to the HA gels without SDS. The swelling behaviors of HA and SHA gels in aqueous solutions and in 0.1 mol/L NaCl were studied, respectively. The HA gels were not soluble in water, and almost no weight loss was detected during the purification and swelling processes. However, SDS could escape from the hydrogel networks into water, leading to the unique process of swelling-deswelling-swelling equilibrium; in brine, both of the HA gel and SHA gel show the swelling curves just like those of chemical cross-linked hydrogels because the hydrophobically association strength of the physical cross-linked units are strengthened by introduction of NaCl. Moreover,the HA gels couldn't heal themselves at room temperature. However, the SHA gels exhibited well self-healing ability, and the self-healing effect could be improved by adjusting the SDS and polymer contents.