Preparation and characterization of inclusion complexes of beta-cyclodextrin with ionic liquid.

The solubilities of beta-cyclodextrin (beta-CD), ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6), and their mixture in water were determined, and the conductivity of these aqueous solutions was measured. It was demonstrated that beta-CD and bmimPF6 could enhance the solubility of each other, and the solubility curves of each were linear with gradients of about 1. The conductivity decreased remarkably with increasing beta-CD concentration, and a discernible break in the conductivity curve could be observed when beta-CD and bmimPF6 were equimolar in the solution. The solubility and conductivity results indicated that inclusion complexes (ICs) of 1:1 stoichiometry were formed. The inclusion compounds were further characterized by using powder X-ray diffraction (XRD) analysis, 13C CP/MAS (cross-polarization magic-angle spinning) NMR and 1H NMR spectroscopy, and thermogravimetric analysis (TGA). The results showed that the ICs were a fine crystalline powder. The host-guest system exhibited a channel-type structure and each glucose unit of beta-CD was in a similar environment. The decomposition temperature of the ICs was lower than that of bmimPF6 and beta-CD individually.

Molecular interaction in binary surfactant mixtures containing alkyl polyglycoside.

Surface tensions were measured for several binary mixtures of a multidegree polymerized alkyl polyglycoside, C12G1.46' with different types of surfactants in 0.1 M NaCl at 25 degrees C. Based on regular solution theory, using a dimensional crystal model and a phase separation model, the molecule exchange energy in mixed monolayer formation (epsilon) and mixed micellization (epsilon(m)) were determined. Surfactants used in the mixtures with C12G1.46 in this study are C12E3S (trioxyethylenated dodecyl sulfonate), C12TAC (dodecyl trimethylammonium chloride), BE-6 (hexaoxyethylenated trisiloxane surfactant), and TMN-6 (hexaoxyethylenated-2,6,8-trimethylnonanol). The mixtures show exchange energy in mixed monolayer formation (epsilon) and mixed micellization (epsilon(m)) ranging from -660 to -1410 J/mol, indicating a decrease in surface energy upon mixing. The decreases in surface energy are in the order C12G1.46/C12E3S > C12G1.46/C12TAC, C12G1.46/C12TAC > C12G2/C12TAC and C12G1.46/BE-6 > C12G1.46/TMN-6. The ability of the mixed monolayer formation relative to the mixed micelle formation of the same binary mixture, measured by the (epsilon-epsilon(m)) values, is in the order C12G1.46/BE-6 > C12G1.46/TMN-6 > C12G1.46/C12E3S-->0 > C12G1.46/C12TAC.

Spontaneous vesicle formation and vesicle-tubular microstructure transition in aqueous solution of a poly-tailed cationic and anionic surfactants mixture.

Spontaneous vesicle formation has been observed in aqueous mixtures of tri-(N-dodecyldimethylhydroxypropylammonium chloride) phosphate (PTA) and bis-(2-ethylhexyl) sulfosuccinate (Aerosol OT), which is supported by negative-staining TEM and dynamic light scattering. The range of vesicle formation in the PTA/AOT mixtures is wide and monodisperse vesicles are obtained. The vesicle diameter increases with the total surfactant concentration. Tubular microstructures, vesicle fusion, and vesicle-tubular microstructure transition have been also observed by negative-staining TEM. The vesicle formation mechanism is discussed from the viewpoint of molecular geometry, conformation, and the interaction between surfactant molecules.

The surface potential of a spherical colloid particle: functional theoretical approach.

By using the iterative method in functional analysis, the potential of the electrical double layer of a spherical colloid particle, which is represented by the so-called Poisson-Boltzmann (PB) equation, has been solved analytically under general potential conditions. With the help of the diagram method in mathematics, the surface potential of the particle has been defined from the second iterative solution. The influence of the parameters included in the solutions on the surface potential has been studied. The results show that the surface potential of the particle increases as the temperature of the system, the aggregation number, and the concentration of ions increase, but decreases with an increase in the dielectric constant and the valence of the ions. The corresponding space charge density also has been illustrated in this work.