Full equilibrium phase diagrams are presented for two ternary systems composed of the cationic surfactant dodecyltrimethylammonium bromide (DTAB), water (D2O) and a cyclodextrin, either β-cyclodextrin (β-CD) or (2-hydroypropyl)-β-cyclodextrin (2HPβCD). 2H-NMR, SAXS, WAXS and visual examination were used to determine the phase boundaries and characterize the nature of the phases formed. Additionally, diffusion 1H-NMR was used to investigate parts of the diagrams. The water solubility of 2HPβCD is 80%(w/w), whereas it is only 1.85%(w/w) for β-CD. Solubility increases for both species upon complexation with DTAB; while the increase is minute for 2HPβCD, it is dramatic for β-CD. Both systems displayed an isotropic liquid solution (L1) one-phase region, the extension of which differs extensively between the two systems. Additionally, the DTAB:2HPβCD:water system also comprised a normal hexagonal (H1) area, which was not found for the DTAB:β-CD:water system. In the DTAB:β-CD:water system, on the other hand, we found co-crystallization of DTAB and β-CD. From this work we conclude that DTAB and CD molecules form 1:1 inclusion complexes with high affinities. Moreover, we observed indications of an association of 2HPβCD to DTAB micelles in the isotropic solution phase, which was not the case for β-CD and DTAB micelles. This is, to our knowledge, the first complete phase diagrams of surfactant-CD mixtures; as a novel feature it includes the observation of co-crystallization at high concentrations.

New amphiphilic pyrimidinic (AP) compounds with two ammonium head groups and different kinds of counterions, inorganic bromide anions (APB) and hydrophobic tosylate anions (APT) were synthesized. Self-organization in these systems has been studied by methods of tensiometry, conductometry, potentiometry and NMR spectroscopy. The critical micelle concentrations (cmc's) of bola-type surfactants are only a little lower than those of cetyltrimethylammonium (CTA) analogues. For both pairs APB/CTAB and APT/CTAT the counterion binding is stronger for the conventional cationic surfactants as compared to 'bola' pyrimidinic surfactants. Unlike the CTAT micelles no sharp micellar growth occurs with the APT concentration. The geometry of AP compounds is assumed to be mainly responsible for the above finding. A branched molecular architecture prevents a close packing of the monomers in the bulk solution and at the interface producing a steric hindrance around the head groups.

The addition of amphiphiles grafted with polyethylene glycol units to constructs of DNA-amphiphiles is of most relevance for applications demanding colloidal stability. In this work, we study the self-assembly behavior of a true ternary mixture comprising (i) an electroneutral complex of DNA and a cationic surfactant (dodecyltrimethylammonium, DTA),(ii) water, and (iii) nonionic surfactant (dodecyl tetraethylene glycol, C(12)EO(4); and dodecyl octaethylene glycol, C(12)EO(8)). The phase diagrams of the two systems: DNA-DTA/C(12)EO(4)/water and DNA-DTA/C(12)EO(8)/water were carried out using (2)H NMR, and small-angle X-ray scattering (SAXS). In both mixtures, the DNA-DTA complex incorporates the postadded nonionic surfactant and large liquid crystalline regions were found. The supramolecular assemblies evolve from a 2D hexagonal structure of the normal type to a lamellar phase as the content of nonionic surfactant is increased. The effect of ethylene glycol unit size in the phase behavior is discussed. We suggest that when longer ethylene glycol units (C(12)EO(8) vs C(12)EO(4)) are used, the DNA-DTA aggregate gets saturated with the nonionic surfactant and there exists a coexistence of a fully swollen mesophase phase of C(12)EO(8) alone presumably of the normal hexagonal type with the lamellar and hexagonal phases of DNA-DTA/C(12)EO(8)/water.

The self-assembly behavior of a cationic surfactant (dodecyltrimethylammonium, DTA) with DNA as counterion in mixtures of water and n-alcohols (decanol, octanol, hexanol, butanol, and ethanol) was investigated. The phase diagrams were established and the different regions of the phase diagram characterized with respect to microstructure by (2)H NMR, small-angle X-ray scattering (SAXS), and other techniques. The DNA-DTA surfactant is soluble in all of the studied alcohols, showing increased solubility from decanol down to ethanol. All of the phase diagrams are analogous with respect to the occurrence of liquid crystalline (LC) regions, but the area of the LC region increases as one goes from decanol to ethanol. In all phase diagrams, hexagonal phases (of the reversed type) for the alcohol-rich side and lamellar phases for the other side were detected. For balanced proportions of the components, there is a coexistence of the lamellar and the hexagonal phase, here detected with a double quadrupole splitting in the (2)H NMR spectra. The correctness of the phase diagrams is confirmed by the fact that along the tie-lines the splitting magnitude remains nearly constant. All of the alcohols except for ethanol act as cosurfactants penetrating the DNA-DTA film. Adding salt to the ternary mixtures causes an increase in the unit cell dimension of the lamellar and the hexagonal phases. The phase diagram becomes more complicated when butanol is used for the alcohol phase. Here, there is the occurrence of a new isotropic phase with some properties analogous to those of the disordered sponge (L3) phase obtained for simple surfactant systems.