1 Two hydrophobic tails can be either symmetric (m–s–m) or asymmetric (n–s–m), where m, n and s denotes two different chains and the spacer accordingly. The gemini molecule contains two aliphatic chains, two hydrophilic heads, and a spacer group. 1 Introduction Gemini surfactants at the molecular level consist of a dimer of two monomeric surfactants. The existence of a slow exchange between two environments, an aggregate and aqueous environment, was confirmed by 1H NMR and 2D HSQC NMR spectroscopy. We indicated that the distribution of aggregate size becomes small and the system becomes homogeneous at much larger concentrations than CAC (typically 15–20 mM). The accurate CMC values could not be identified for the systems in the study. A broad transition region was observed, and stable micelles were obtained at much higher concentrations than CAC. The obtained CC values are identified as critical aggregation concentrations CAC. The morphology of the aggregates was characterized by small-angle scattering of synchrotron radiation and molecular dynamics simulations. The micelle aggregation numbers were estimated from the self-diffusion coefficients and were independently confirmed using steady-state fluorescence quenching. The critical concentrations CC were independently obtained from surface tension, electric conductivity, UV-Vis and NMR methods. We employed Nuclear Magnetic Resonance diffusometry and Bayesian DOSY analysis to obtain the aggregate size distribution in the transition region.
MESTRENOVA PENN CHEM SERIES
The aggregation behavior in the transition region was studied for a series of dicationic surfactants 3,3′-bis(1-dodecylimidazolium)dichlorides with varied spacer length from two to twelve carbon atoms.
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