Aggregation behavior of latex particles in shear flow confined between two parallel plates.

In this study, the aggregation and breakup behaviors of latex particles in shear flow confined between two parallel plates were investigated using an in situ observation apparatus with a laser scanning confocal microscope. To investigate the effects of shear rate and the gap width between two parallel plates on the size and structure of the aggregates in the steady state, the distributions of the projected cross-sectional area and perimeter-based fractal dimension of the aggregates were measured. As a result, the average size of the aggregates decreases as shear rate increases and the gap width decreases due to the hydrodynamic effect acting on the aggregates. The size distributions of the aggregates become narrow as the gap width decreases. In addition, the fractal dimension, that is, the structure of the aggregates, was almost independent of shear rate and the gap width and approximately 1.2, which suggests that the aggregates are relatively compact.

Polymer-coated liposomes resistant to enzymatic hydrolysis.

A polymerizable electrolyte, 2-aminoethyl 1,6-heptadien-4-yl phosphate (AEHDP), which has the same hydrophilic head group as naturally occurring phospholipids, was prepared. Five equivalents of AEHDP were added to a suspension of liposomes (closed bilayer vesicles made of phospholipids) and layered on the liposomes. After polymerization by UV irradiation, the resulting polymer-coated liposomes were resistant to hydrolysis of their constituent phospholipids by phospholipase A2.

Electrohydrodynamic effect on phase separation morphology in polymer blend films.

We have investigated the effect of electrohydrodynamic (EHD) convection on the domain structure in a polystyrene (PS)/polyvinyl acetate (PVA) blend film to demonstrate the feasibility of using the EHD effect as a means of mixing and morphology control in a polymer blend film prepared by solvent evaporation. Here, polymers-toluene solutions were spread on a glass substrate with patterned electrodes to apply a dc electric field, and well-defined structures of EHD convection were formed in the polymer solutions. As a result, regular patterns were formed in the PS/PVA polymer blend film in which PVA-rich domains were confined within each unit of patterned electrodes, i.e., between positive and negative electrodes, at an appropriate electric voltage. In addition, it was demonstrated that such novel morphology is not due to the wetting/dewetting effect of polymer components to the Pt electrodes deposited on the glass substrate, by experiments with a SiO2-covered substrate.