Studies on the interaction between tetradecyl dimethyl betaine and sodium carboxymethyl cellulose by DPD simulations

The dissipative particle dynamics (DPD) simulation method has been used to investigate the effect of pH value on the interaction between tetradecyl dimethyl betaine (C14BE) and sodium carboxymethyl cellulose (Na-CMC) in aqueous solution. The simulation results indicate that C14BE/Na-CMC aggregate does not form at pH = 7 (the isoelectric point pI of C14BE is 5), but at pH = 2 typical C14BE/Na-CMC aggregate is observed, which means the interactions between them get stronger. Furthermore, at pH = 2 the curve of the end-to-end distance of Na-CMC chain as a function of C14BE volume fraction initially increases, then reduce and finally increase; while at pH = 7 its end-to-end distance remains constant. The results of surface tension measurements are consistent with DPD simulation results. It is concluded that DPD simulation method can provide some important information on surfactants and macromolecules at the molecular level.