Phase behavior of didodecyl and dioctadecydimethylammonium bromide (DDAB and DODAB) in water was studied using X-ray techniques, differential scanning calorimetry and deuterium nuclear magnetic resonance measurements. Both surfactants self-assemble into lamellar liquid crystalline, either Lα (fluid) and Lβ (gel), phases. The gel-to-fluid phase transition temperature (Tm) in DDAB lamellae was fo...

The phase behavior of a melt of monodisperse rod-coil diblocks is studied. We derive a Landau free energy functional for both a compositional and a nematic order parameter. The excluded volume interaction between the rod blocks is modeled by an attractive Maier-Saupe interaction. The incompatibility between rodand coil blocks is modeled by the usual Flory-Huggins interaction. For a large volume...

We study theoretically the lamellar-disorder-lamellar phase transitions of AB diblock and tetrablock copolymers confined in symmetric slitlike pores where the planar surface discriminatingly adsorbs A segments but repels B segments, mimicking the hydrophobic/hydrophilic effects that have been recently utilized for the fabrication of environmentally responsive "smart" materials. The effects of f...

The behavior of purified egg lecithin in water has been investigated in relation to the quantity of water present and the temperature. The complete binary phase diagram of egg lecithin-water is presented as well as X-ray diffraction data on selected mixtures. Dry egg lecithin is present in at least partially crystalline form until about 40 degrees C. Above this temperature it forms a "wax-like"...

Extensions of a previously presented Landau-de Gennes type liquid crystalline phase transition model for the direct isotropic/smectic-A (lamellar) a phase transition to the direct isotropic/smectic-C (tilted lamellar) transition are studied. Two different proposed extensions to the model are studied both in the context of ideal ordering (point volume) and full three-dimensional uniaxial scalar/...