Determination of the Structure of Tetradecyldimethylaminoxide Micelles in Water by Small-Angle Neutron Scattering

Abstract

By means of a small-angle neutron scattering experiment the radius R as well as the scattering length density of rodlike tetradecyldimethylaminoxide (TDMAO) micelles in D 2 O were determined. The micelles turned out to be homogeneous. As a function of the concentration c of TDMAO we found the mean aggregation number 〈N〉, which increases with c, and the value of two thermodynamic parameters describing the energy advantage by inserting a monomer in the end cap of the spherocylindrical micelles and in the cylindrical part, respectively.

Interaction between poly(ethylene glycol) and two surfactants investigated by diffusion coefficient measurements

“…Electric birefringence experiments show that an increasing surfactant concentration leads to a sphere-to-rod transition at around 10 mM [4]. Small-angle neutron scattering experiments (SANS) confirm the existence of cylindrical micelles for the higher surfactant concentrations [14]. The polydispersity index obtained by this technique is in the range 0.4-0.8 [14].…”

“…Small-angle neutron scattering experiments (SANS) confirm the existence of cylindrical micelles for the higher surfactant concentrations [14]. The polydispersity index obtained by this technique is in the range 0.4-0.8 [14].…”

“…Tetradecyldimethyl aminoxide (C 14 DMAO) which was recrystallized twice, was a gift from Dr. H. Hoffmann. It is a zwitterionic surfactant but behaves like a non-ionic in neutral or al- kaline solutions as in our case [4].…”

“…This result comes from the fact that below 10 mM, the pure surfactant micelles are spherical, while above 10 mM, they are cylindrical [4,14]. The growth and the change of shape of the micelles explain the variation of their mobility, as a function of surfactant concentration, in the pure surfactant system.…”

Protonation Behavior and Stability of Micelles of N-Lauroylaminoalkyl-Dimethylamine Oxides-Effects of Added Salt Concentration and Spacer Length

“…The solution properties and the surface properties also vary with pH. The pH (the protonation degree) dependence of the various solution properties, such as the titration behavior [1][2][3][4][5][6][7][8][9][10][11] , the critical micelle concentration (cmc) [12][13][14][15][16][17] , the micelle aggregation number 18,19) , the micelle size 7,18,20) , and the aggregate structures [21][22][23][24][25][26] , received much attention. In particular, it is noteworthy that the cmc values and the micelle aggregation number for dodecyldimethylamine oxide (C12DMAO) showed minimum and maximum, respectively, when the degree of ionization, a, is around 0.5 (that is, cationic species: nonionic species ≈ 1:1) 19) .…”