We prepared poly(vinylidene fluoride) (PVDF)/multiwalled carbon nanotube (MWCNT) nanocomposites using the electrospinning process and investigated the effects of varying the MWCNT content, as well as the additional use of drawing and poling on the polymorphic behavior and electroactive (piezoelectric) properties of the membranes obtained. Fourier transform infrared spectroscopy and wide-angle X-ray diffraction revealed that dramatic changes occurred in the β-phase crystal formation with the MWCNT loading. This was attributed to the nucleation effects of the MWCNTs as well as the intense stretching of the PVDF jets in the electrospinning process. The remanent polarization and piezoelectric response increased with the amount of MWCNTs and piezoelectric β-phase crystals. A further mechanical stretching and electric poling process induced not only highly oriented β-phase crystallites, but also very good ferroelectric and piezoelectric performances. In the drawn samples, the interfacial interaction between the functional groups on the MWCNTs and the CF 2 dipole of PVDF chains produced a large amount of βphase content. In the poled samples, the incorporation of the MWCNTs made it easy to obtain efficient charge accumulation in the PVDF matrix, resulting in the conversion of the α-phase into the β-phase as well as the enhancement of remanent polarization and mechanical displacement.

In this article, we considered experimentally the deformation and breakup of Newtonian and non-Newtonian conducting drops in surrounding fluid subjected to a uniform electric field. First, we examined three distinctive cases of Newtonian-fluid pairs with different relative conductivities, namely highly conducting drops, conducting drops and slightly conducting drops. The results on the Newtonian fluids demonstrated that when the conductivity of the drop is very large relative to that of the surrounding fluid, the deformation response of such highly conducting drops is described well by the electrohydrostatic theory, especially with regard to the prediction of the critical point. Specifically, when the ratio of drop to continuous-phase resistivity, R, was less than 10 −5 , the electrohydrostatic theory was quite satisfactory. Then, the non-Newtonian effect on the drop deformation and breakup was studied for highly conducting drops which satisfied the condition R < O(10 −5 ). The highly conducting drop became stable in a weak or moderate field strength when either the drop or the continuous phase was non-Newtonian. On the other hand, when both the phases were non-Newtonian, more complicated responses were observed depending on the ratio of zero-shear-rate viscosities. Although the effects of the rheological properties are minimal on all features away from the critical conditions for breakup or prior to the instability, the non-Newtonian properties have a significant influence during drop burst, which is accompanied by large velocities and velocity gradients. In particular, when the ratio of the zero-shear-rate viscosity of the drop to that of the ambient fluid was much larger than unity, non-Newtonian properties of the drop phase enhanced the drop stability. Conversely, the elasticity of the continuous phase deteriorated the drop stability. Meanwhile if the zero-shear-rate viscosity ratio was much smaller than unity, the elasticity of the continuous phase produced a stabilizing effect. The effects of resistivity and viscosity ratios on the breakup modes were also investigated. When at least one of the two contiguous phases possessed considerable non-Newtonian properties, tip streaming appeared.

We describe the preparation and characterization of core-shell latex particles, consisting of a polystyrene core, covered with a perfluoroalkyl acrylate shell. The core-shell particles were prepared by a two-stage emulsion polymerization under kinetically controlled conditions and were characterized by transmission electron microscopy, differential scanning calorimetry, and X-ray diffraction analysis. The surface properties of the latex films produced from the core-shell particles were investigated by the contact angle method. Compared with random copolymers or latex blends of styrene and perfluoroalkyl acrylate, the core-shell particles were the most effective to reduce the surface energy of the latex films. The effect of acetone as a cosolvent on the polymerization process was also considered.

The surface properties of latex films prepared from heptadecafluorodecyl acrylate and 2,2,2trifluoroethyl methacrylate copolymers were investigated in terms of hydrophobicity and sliding behavior of liquid droplets. The hydrophobicity of fluorinated latex films evaluated from water contact angle was closely related to the chemical composition of the surface. On the other hand, the sliding angle of liquid droplets was not directly proportional to the hydrophobicity or oleophobicity of the latex films in the present study. Although the hydrophobicity of copolymer latex films was significantly enhanced by adding small amount of highly fluorinated heptadecafluorodecyl acrylate, it made water droplets rather difficult to slide down on an inclined surface. The sliding angle of water droplet was quite sensitive to the preparation methods, namely, batch and semicontinuous emulsion polymerizations in contrast to the hydrophobicity. The surface morphology and roughness of the latex films were found to be important to explain the observations.

In this article, we investigated the electrohydrodynamic responses of a deformable fluid drop in another immiscible fluid under the action of a dc electric field. Both the ambient and drop fluids considered here were incompressible Newtonian and all of the drop phases were less conductive than their ambient fluids. Under these circumstances, the drops experienced the so-called electrorotation owing to the reverse dipole generated by the external electric field when the electric field strength exceeded a certain threshold value. The experimental observation showed that the threshold electric field strength was dependent on the drop size as well as the viscosity ratio. Also noted was the effect of the electrorotation on both the deformation behavior and the mode of the drop breakup. Specifically, we determined the critical electric capillary number beyond which the steady-state drop shape did not exist and the drop eventually broke up. Finally, the validity of Taylor's leaky dielectric theory was discussed in the presence of the electrorotation of the drop.