Monodispersed metal (hydrous) oxides - a fascinating field of colloid science

Phase separations in dispersions of different types of spherical, lyophilic, monodisperse silica particles and polystyrene molecules in cyclohexane at the theta temperature were investigated. We used silica particles stabilized with a chemically bonded layer of stearyl alcohol molecules and silica particles stabilized with tetraethylenepentamine-terminated polyisobutene molecules. At a fixed silica concentration (1.0 or 5.0% w/v) a liquid-liquid phase separation occurs above some limiting polystyrene concentration. The limiting concentration, c lim , usually is of the order of a few percent (w/v), and depends on the molar mass of the polymer. High-molar-mass polymers show a lower c lim value than low-molar-mass polymers. An increase in the concentration of the silica particles lowers the c lim value. The radius of the silica particles also influences c lim . The experimental results are interpreted in terms of a simple “hard sphere-cavity” model, with which a theory is worked out which is based on first principles only. Most experimental results can be reproduced by theoretical calculations on a semiquantitative scale. Discrepancies between theory and experiment only are found with the silica samples that obviously do not conform to the hard sphere model used.

Interactions in mixtures of colloidal silica spheres and polystyrene molecules in cyclohexane

Biotechnological Applications Jose Ramos,† Jacqueline Forcada,*,† and Roque Hidalgo-Alvarez*,‡ †POLYMAT, Bionanoparticles Group, Departamento de Química Aplicada, UFI 11/56, Facultad de Ciencias Químicas, Universidad del País Vasco UPV/EHU, Apdo. 1072, 20080 Donostia-San Sebastiań, Spain ‡Grupo de Física de Fluidos y Biocoloides, Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Granada, 18071 Granada, Spain

Cationic Polymer Nanoparticles and Nanogels: From Synthesis to Biotechnological Applications

Heteroaggregation in colloidal dispersions

The forced convection of a monodisperse, monoclonal suspension of bacteria through a uniform, saturated porous medium has been investigated. Bench-scale column studies were carried out to measure the removal of microorganisms from suspension due to attachment to the surfaces of the solid phase. The columns were packed with 40-μm borosilicate glass beads, and bacterial sorption was measured as a function of depth in the column using a leucine radiolabel assay. The strains A1264 and CD1 were examined separately. Colloid filtration theory was used to interpret the data, and the average, or effective, affinity of the bacteria for the glass beads was found to decrease with distance traveled through the column. It is postulated that, under these circumstances, the cell/collector affinity (that is, the collision efficiency α) varied due to intrapopulational differences in bacterial surface characteristics. A simple bimodal probability density function, consisting of two Dirac delta functions, was found to satisf...

Hiroshi Sasaki

Papers

Heterocoagulation. VI. Interactions of a monodispersed hydrous aluminum oxide sol with polystyrene latex