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 couldnt 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.