Decane structure on a graphite surface with sodium dodecyl sulfate and betaine surfactant mixtures: A molecular dynamics study

Computer simulations of anionic and zwitterionic surfactants were carried out to study decane molecules arrangement on a graphite surface. Systems were constructed with different amount of decane molecules deposited on top of the graphite surface by forming two and four structured layers. Then, Sodium dodecyl sulfate (SDS) and two betaine surfactants, cocoamidopropyl (CAPB) and the N-Dodecyl-N,N-dimethyl-3-ammomio-1-propanesulfonate (SB3-12), with their mixtures were used to investigate removal of the alkane molecules where different features were observed. Arrangement was analyzed in terms of density profiles and isotherm curves at different surfactant concentrations. It was observed that all surfactants promoted the formation of an additional decane layer suggesting they could produce detachment or removal from the graphite surface. The anionic surfactant present better removal from the surface than the betaine ones whereas in the case of the mixtures the SDS/CAPB one was slightly better than the SDS/SB3-12 one.