Swelling and adsorption properties of hydrophobic poly [(N-(3-(dimethylamino)propyl)methacrylamide)-co-(lauryl acrylate)] hydrogels in aqueous solutions of surfactants

The swelling and adsorption behavior of a series of hydrophobic poly [(N-(3-(dimethylamino)propyl)methacrylamide)-co-(lauryl acrylate)] [P(DMAPMA-co-LA)] hydrogels was studied as a function of temperature in aqueous solutions of the anionic surfactant sodium dodecyl sulfate (SDS) and the cationic, surfactant dodecyltrimethylammonium bromide (DTAB). Between 0 and 41.7 mol-% of lauryl acrylate (LA) were used as a hydrophobic comonomer in the hydrogel synthesis. In SDS solutions, the equilibrium swelling ratio of the hydrogels decreased with increasing temperature. At SDS concentrations below 0.0083 m, the hydrogels exhibited an almost linear swelling behavior. However, for SDS concentrations above 0.0083 m, non-linear swelling behavior was observed in the range 28-36 degrees C. In contrast to the SDS solutions, in all DTAB solutions the equilibrium swelling ratio of the hydrogels increased with increasing temperature and a positive temperature sensitive property was shown for all P(DMAPMA-co-LA) hydrogels. The adsorption capacities of the hydrogels in aqueous solutions of SDS and DTAB were determined via surface tension measurements. An increase in the LA content in the hydrogel caused an increase in the amount of adsorbed surfactant molecules in both media.