I need to know whether palisade layer composed of sole TX-100 is more rigid or softer that this composed of TX-100 with cosurfactant BuOH.
Dear Jakub, it was some time since I was doing Dynamic NMR measurements in systems with surfactants, but surely you could determine the mobilities in microemulsions by FT-PGSE Multicomponent Diffusion measurements or simply by measuring T1 or T2 relaxations by NMR on ordinary NMR spectrometers. / Johan Carlfors at : www.ontargetchemistry.com Uppsala, Sweden.
If you do Small angle xray scattering measurements and fit to Calle model, you can extract the bending modulii of the membranes.
Dear, Jakub, it just struck my mind that the cmc of surfactants are an easy an strong indicator of the layers formed in micelles. The lower cmc, the better packing of the surfacant chains. Therefor I would guess that the system of the two, with the lower cmc is probably more efficiently packed, having more favourable interactions between the molecules, making the layer more stable.
Dear Johan.
I realize that CMC indicates which system is characterized by more favourable interactions. But the point is that, as I see it, CMC reflects two contributions - film curvature fluctuations (in case of flexible film) compensates the change in entropy or entropy compensates bending energy of surfactant film. And basing on a simple change of CMC we can't (???) state, which contribution is the driving one.
Dear Jakub, being a more practical chemist, basing most of my knowledege from many years at the lab, I stll belive that even micellar formation results from escaping energetic water-alkyl intercations and hindered by steric and, for ionics, el-static repulsions. The net effect is reflected in the cmc. Therefor I think that a lower cmc reveals that the net effect of the micellar process is favourable. If micellar formation is favourable, to me this means that the interactions between the surfacant molecules cost less energy, leading to a closer packing, leading to less flexible interfacial layer of surfactant molecules. I still sure that it most conveniently and most reliable can be proved by NMR. In this case, LS is less reliable since it includes tthat more assumptions have to made before evaluating the results. NMR directly monitor molecular dynamics. / J o h a n
Discussing cmc for comparison TX-100 and TX-100 n?-butanol is very tricky. How to compare concentration, neglecting butanol? Further, n-butanol is partly soluble in water, i.e. will partly act as cosolvent.
Hmmm . . . . Good point ! - Must think. Now, busy at work, evaluating results from yesterday's ZetaSizer measurements. I'll return a s a p
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