Experimental and theoretical study of symmetric dimeric oligomers

Abstract

Although multiple families of gemini surfactants have been studied in the literature. Meaningful structure performance relationships are limited to a single family. As such building a model to readily study dimeric surfactants may provide a means for structural performance evaluations of experimentally synthesized surfactants and their computationally generated counterparts. The bending of the interchange arm of gemini or dimeric surfactants has been studied in a dynamic computational model. Conformational behaviour of the surfactants in simulation have been assessed via radial distribution functions or “RDFs”. The results indicate the longer spacers can loop towards the aggregate interior and interact with the protons on the carbon atoms near the end of the main surfactant chains, whereas these interactions are absent for the shortest spacer dimeric studied. These conformational patterns suggested from the RDF results have been compared to experimentally determined conformations and orientation of a series of dicationic dimeric amphiphiles of the type N,N’-bis (dimethylalkyl)-a,ω-alkanediammonium dibromide (m-s-m) in aggregated form via 13C chemical shift measurements and 2D-rotating frame Overhauser enhancement spectroscopy (2D-ROESY). Using the non-mixed systems as a reference point, the conformational behaviour of mixed systems of surfactants has been contrasted.