Ryuji Aizawa

Simple synthesis of water-soluble conducting polyaniline

Abstract A water-soluble externally (HCl)-doped conducting polyaniline (ED-SPAN) is prepared by such a simple synthetic method that emeraldine salts are sulfonated by chlorosulfonic acid in dichloroethane at 80°C and subsequently hydrated in water at 100°C. Sulfonating any emeraldine salts (counter anion X− = Cl−, SO42−, and BF4−) or emeraldine base results in the production of HCl-doped sulfonated polyaniline, where HCl dopant from hydrolysis of chlorosulfonic group exchanges with the original dopant. The degree of sulfonation, namely, sulfur-to-nitrogen (S/N) ratio, can be controlled by adjusting the amount of chlorosulfonic acid. With increasing S/N ratio from 0.65 to 1.3, the solubility in neutral water increases from 22 to 88 g/l and the four-probe conductivity for a compressed pellet decreases from 0.023 to 1.7 × 10−5 S/cm, showing sulfonation-induced undoping.

ER Suspensions of Sulfonated Poly(Styrene-CO-Divinylbenzene) Particles

Two ER suspensions (ERF1 and ERF2) containing highly sulfonated poly(styrene-co-divinylbenzene) particles (ERP) were newly prepared. The ERP concentration was 20 wt% in ERF1 and 40 wt% in ERF2. The ER properties of the suspensions were investigated in view of applications to practical devices. The investigated properties were zero-field viscosity, dispersion stability, induced shear stress, current density, response time, shear rate and temperature dependence of the induced shear stress and current density, response time, shear rate and temperature dependence of the induced shear stress and the current density. electrical durability. In the results, it was found that ERF1 and ERF2 had a very high potential for practical applicatons. The remarkable characteristic of ERF1 was the very low zero-field viscosity of 35 mPa·s at 25°C. The remarkable characteristic of ERF2 was very large induced shear stress and under applying DC 4 kV/mm at 25°C, the induced shear stress was 5.1 kPa. As an application example, the ERFs can be efficiently used for an ER Cutting Machine incorporating variable speed rodless cylinders. The machine has worked smoothly for one and a half years, although the characteristic of control slightly changed.

HYSTERESIS PHENOMENON IN FLOW-CURVES OF ER FLUIDS CONTAINING SULFONATED POLYMER PARTICLES

The ER fluids containing sulfonated polymer particles were continuously sheared at increasing and decreasing shear rates using a rotary concentric cylinder rheometer and the hysteresis in the up- and down-flow-curves were analyzed. The ER fluids show hysteresis of shear stress and current density. The up-curve (when shear rate increased) was located below the down-curve (when shear rate decreased). As the electric field increased, the area in the hysteresis curves increased. The hysteresis depended on the electric field strength, the time of the applied electric field, the volume fraction of particles and the water content of the particles. Hysteresis phenomenon was explained, based on the formation of agglomerations of dispersed particles in the ER fluid and on changes of the lamellar formations

Properties of Electrorheological Fluids Containing Numerously Sulfonated Polymer Particles

Of great interest is that electrorheological (ER) fluids are put in practical use.1,2,3 In order that an ER fluid can be utilized in a variety of applications, the ER fluid needs to meet several requirements all together.4,5 At the present time, no ER fluid is likely to fill all of those requirements. It is well-known that ER fluids containing hydrophilic particles with small amounts of moisture induce a relatively large shear stress under an electric field.6,7,8 However, when the electric field is continuously supplied to the ER fluid, a concurrent current density gradually increases and finally dielectric breakdown occurs. In order to put the ER fluids in practical use, they have to show good durability.

STEADY AND TRANSIENT RESPONSES OF ELECTRORHEOLOGICAL SUSPENSION PASSING THROUGH A RECTANGULAR CHANNEL

The steady and transient responses of ER effect of ER fluids containing sulfonated polymer particles, passing through a rectangular channel between two fixed parallel electrodes, were investigated by ensuring pressure drops across the channel in which the flow established a Poiseuille flow geometry. Effects of the types and the strength of applied electric field and the mean flow velocity on the steady response were clarified, and compared with those in a Couette flow geometry using a rotary rheometer in order to investigate the dependence of ER effects on the flow geometry. As the mean flow velocity increased, the yield stress decreased exponentially under DC voltage, while, in the case of AC voltage, gradually increased and reached a peak level and decreased thereafter. Contrastively, the yield stress measured by the rotary rheometer decreased suddenly at low shear rate, and reached almost constant level. That is, the measured yield stress depends on the flow geometry and the type of applied electric field. The measured pressure response to a step input voltage can be approximated by a first order response, and the rising time constant of ER effect depend on the compositions of ER fluids and range from 5 to 40 msec.

Dynamic Viscoelasticity in Oscillatory Slit Flow of an ER Suspension Containing Sulfonated Polymer Particles

An oscillatory slit flow type rheometer has been developed to measure the dynamic viscoelasticity in an oscillatory slit flow of an ER fluid. Using the rheometer, an ER suspension of numerously sulfonated polymer particles in an insulating oil is evaluated. The results are compared with those for the oscillatory shear flow. In the slit flow, the dynamic viscoelasticity of the ER suspension mainly depends on the fluid strain amplitude and the applied electric field strength. In the fluid strain amplitude of less than about 50% the viscoelastic property becomes dominant, while in the fluid strain amplitude of more than that the viscoelastic plastic property dominates. As the applied field strength increases, the dynamic viscoelasticity changes from viscoelastic plastic to linear viscoelastic. In an oscillatory shear flow, on the other hand, the dynamic viscoelasticity of the ER suspension largely depends on the fluid strain and hardly on the applied field strength. The differences between the dynamic viscoelasticity in the two flow modes can be explained based on the formation and deformation of ER particle clusters which span the electrodes.

PROPERTIES OF ELECTRORHEOLOGICAL FLUIDS CONTAINING SULFONATED POLY(STYRENE-CO-DIVINYLBENZENE) PARTICLES

Two series of sulfonated poly(styrene-co-divinylbenzene) particles (SSD), different in average particle diameter and in sulfonic acid substitution level were synthesized. The vertical sectional views of the SSD particles showed that the sulfonic acid groups were uniformly distributed all over the SSD particles. The electrorheological behavior of the suspensions of the SSD particles in silicone oil was investigated. Induced shear stress under an electric field increased with the increase of average particle diameter and sulfonic acid substitution level. The sedimentation velocity of the dispersed particles was monotonous with the average particle diameter and the sulfonic acid substitution level. Another series of sulfonated poly(styrene-co-divinylbenzene) particles (SSDH), different in sulfonic acid substitution level, was separately prepared. The vertical sectional views of the SSDH particles showed that the particles had sulfonated surface layer and unsulfonated core. The suspensions of the SSDH particles having the sulfonated layer of not less than 1.4 microns induced similar shear stress at the same electric field strength. The sedimentation velocity of the dispersed particles was lowered with diminishing the thickness of the sulfonated layer.