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Characterization of new gemini surfactant micelles with phosphate headgroups by SANS and fluorescence spectroscopy

Two series of bisphosphate surfactants having different hydrophobic tails and variable number of spacer methylene groups have been synthesized. Detailed small-angle neutron scattering studies were carried out with their aqueous solutions to study their micellar properties. For some of these new surfactants, critical micellar concentrations and micropolarities were also determined. It has been found that the micelles were ellipsoidal for surfactants with short spacers having C12H25 hydrophobic tails. However, the corresponding surfactants having C16H33 chains and similar m-values afforded micelles that were disk-like and rod-like

Transition from disc to rod-like shape of 16-3-16 dimeric micelles in aqueous solutions

Small-angle neutron scattering (SANS) measurements from bis-cationic C16H33N+(CH3)2– (CH2)3–N+(CH3)2C16H33 2Br- dimeric surfactant, referred to as 16-3-16, at different concentrations and temperatures, are reported. It is seen that micelles are disc-like for concentrations C=2.5 and 10 mM at temperature T=30°C. At low concentration C=0.5 mM micelles are rod-like. Similarly, there is a disc to rod-like transition of micelles on increasing the temperature. For C=2.5 mM, micelles are rod-like at T=45 and 70°C.

Small-angle X-ray scattering from micellar solutions of gemini surfactants

Abstract In an earlier work, we had studied small-angle neutron scattering (SANS) from micellar solutions of bis-cationic C 16 H 33 N + (CH 3 ) 2 –(CH 2 ) m –N + (CH 3 ) 2 C 16 H 33 , 2Br − gemini surfactants, referred to as 16- m -16, 2Br − , for several spacer lengths. This Letter reports the results of small-angle X-ray scattering (SAXS) experiments on the above system for spacer lengths of m=3, 4 and 12. It is seen that SAXS distributions are qualitatively different from the SANS distributions. These experiments show that a combined SANS and SAXS study can be used for obtaining information on the counterion distribution around the micelles.

Characterization of vesicles from ion-paired gemini surfactants by small angle neutron scattering

Detailed small angle neutron scattering (SANS) studies were carried out with the aqueous vesicular (unilamellar) suspension of dimeric ion-paired lipids (2a–2c) for spacer lengths corresponding to n-values of 2, 6 and 10 and monomeric ion-paired lipid (3) below and above the phase transition temperature of each amphiphile. The vesicular structure strongly depends on the spacer chain length. The mean vesicle size is smallest for the lipid with a short spacer, n = 3 and it increases with the increase in the spacer chain length. The bilayer thickness also decreases with the increase in the spacer chain length. The size polydispersity increases with the increase in the spacer chain length (n-value).

Synthesis and vesicle formation from novel pseudoglyceryl dimeric lipids. Evidence of formation of widely different membrane organizations with exceptional thermotropic properties

Eight new bis-cationic dimeric lipids 2a–h have been synthesized; TEM of their aqueous dispersions confirmed the vesicle formation and from the thermal, spectroscopic, DLS and XRD studies it has been revealed that they form three different kinds of membranous aggregate depending on the m-value.

Vesicle formation from dimeric surfactants through ion-pairing. Adjustment of polar headgroup separation leads to control over vesicular thermotropic properties

Eight new vesicle-forming dimeric surfactants are synthesized: the polar headgroup separation in such dimeric amphiphiles strongly influences their vesicular thermotropic phase-transition behaviour.

Modulation of vesicular properties by variation of shapes of bolaform counter ions in hybrid-ion paried surfactants

Four new vesicle-forming bolaphile/amphiphile ion pairs are synthesized; the bolaphile shapes in such hybrid systems strongly control their vesicular properties.

Structure of 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9 hexadecafluorodecyl 1,10-ditosylate by X-ray crystallography and 19 F-NMR spectroscopy

2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorodecyl 1,10-ditosylate and its precursors were synthesized and characterized by H-1- and F-19-NMR spectroscopic methods and X-ray crystallography. These compounds are building blocks for the syntheses of the surfactants containing polyperfluoromethylene spacer. The molecule has extended all-trans conformation with molecular symmetry (1) over bar (C-i). There is a reasonably strong C-H ... O interaction in the crystal and there are two F ... F intermolecular contact distances less than the sum of van der Waals radii