Mary Heppenstall-Butler

Na

Directed crystallization is found in many natural systems, where the inorganic material provides the organism with superior barrier and mechanical properties. Using this principle of controlled nucleation and growth on a biopolymer (pectin) substrate, hollow shells of calcium carbonate were formed in certain reaction conditions that were generally...

Crystallization of a CaCO3 thin film from supersaturated solution on chitosan in the presence of poly-acrylic acid was investigated by in situ AFM and SNOM. It was directly observed that crystallization proceeds through characteristic stages consistent with the theory of spherulitic growth: development of individual branches, build-up of larger sca...

Crystallization of two-dimensional spherulitic calcium carbonate films was performed on planar films of chitosan in the presence of poly(acrylic acid) (PAA). PAA, electrostatically bound to the chitosan substrate, increased the local concentration of calcium at the surface, thereby promoting CaCO3 crystallization there. Simultaneously, interaction...

Stearic acid and triethanolamine (TEA) in a molar ratio of 2:1 were mixed in aqueous solution at 80 degrees C and subsequently cooled to ambient temperature. The structural evolution of the resultant sample during storage was characterized by using light microscopy, Cryo-SEM, differential scanning calorimetery, pH, infrared spectroscopy, elemental...

The influence on calcium carbonate crystallization of a series of biopolymers that contain carboxylic acid or sulfate functional groups was studied using pH and turbidity measurements, optical microscopy, and scanning electron microscopy. Without biopolymer, single calcite (104) rhombohedra were formed. In the presence of nongelling biopolymers (xa...

We study the spontaneous size selection in lyotropic cholesteric (W/O) and thermotropic nematic (O/W) liquid crystal emulsions. The droplet sizes have been characterized by dynamic light scattering, which indicates a narrow monomodal distribution of droplets achieved spontaneously even without emulsion filtration. Anchoring of the director, provide...

We studied a new kind of W/O emulsions based on a lyotropic liquid crystal as the aqueous droplet phase. The cholesteric phase, a solution hydroxypropyl cellulose in water was dispersed in the continuous oil matrix, paraffin oil or heptane. We made a specific choice of surfactant in order to impose director anchoring conditions at the oil-water int...

Crystals of partially neutralized stearic acid with triethanolamine (TEA) were prepared by mixing these two materials above 80 degrees C and then cooling. The crystalline composition and the structure and melting behavior of the resultant products were characterized with small-angle and wide-angle X-ray diffraction, thermal analysis, microscopy, an...

The topological stability of emulsions of thermotropic nematic liquid crystal dispersed in water is examined for a wide range of materials and concentrations. There is a characteristic size of emulsion droplets, R* = K/W, determined by the ratio of Frank elastic, K, and surface anchoring, W, energies of the liquid crystal. Nematic droplets below th...

Phase separation mechanisms and kinetics in quiescent and shear conditions were studied using small-angle light scattering, optical polarimetry and confocal laser scanning microscopy in the gelatin/maltodextrin and gelatin/dextran systems. In the former system the temperature quench caused phase separation, which was studied in the gelled and liqui...

The state behavior of stearic acid-sodium stearate-water, which provides a model of a fatty acid structuring mechanism, was studied by differential scanning calorimetry (DSC), optical microscopy, and X-ray scattering. DSC mapped the state diagram of aged and quenched samples as a function of temperature. Optical microscopy identified a liquid cryst...

Small-angle light scattering, turbidity, and confocal laser scanning microscopy were used to study microstructure formation and evolution in a gelatin/dextran mixture. There was a time-delay of up to tens of minutes between reaching the quench temperature and the onset of phase separation, because demixing only occurred once a certain amount of ord...

The kinetics of phase separation were observed in the gelatin/maltodextrin and gelatin/maltodextrin/gum arabic systems, where gum arabic was added as a minority component, using small-angle light scattering, turbidity measurement, and confocal scanning laser microscopy. Phase separation occurred by spinodal decomposition for quenches both above and...

The interface between ultrathin deuterated poly(methyl methacrylate) films on polystyrene substrates is subject to a dispersive force driven instability consisting of thermally excited capillary waves. We have studied this example of liquid/liquid spinodal dewetting, using specular and off-specular neutron reflection measurements to characterize th...

The pull-out behaviour of isotactic polypropylene/Twaron D1056 single-fibre composites was investigated. Three matrix morphology types, two transcrystalline [fast-cooled (FCTC) and slow-crystallized (SCTC)] and one spherulitic [slow-crystallized (SCS)], were compared. The detailed point-to-point stress distributions along the embedded fibres were m...