Dielectric observations on polystyrene microcapsules and the theoretical analysis with reference to interfacial polarization

Abstract

Dielectric measurements were carried out for polystyrene microcapsules which were prepared by means of an interracial polymer deposition technique. The microcapsules showed a couple of dielectric relaxations termed P for lower and Q for higher frequencies. The frequency profiles were characteristic of the structure that shelled spheres were dispersed in a continuous medium. Gelatin aqueous solutions, cationic polyelectrolyte solutions and distilled water were loaded in the capsule interior to examine the effect of conductivities of the constituent aqueous phases on the dielectric properties. Relaxation frequencies of the relaxations P and Q observed were directly proportional to the conductivities of the continuous medium and of the capsule interior, respectively. A dielectric theory was proposed for a suspension of shelled spheres in a continuous phase in order to analyze the relaxation data observed for the microcapsules. Volume fraction of the capsules, relative permittivity and conductivity of the capsule interior and thickness of the capsule wall are evaluated from the dielectric observations by use of the theoretical formulas derived. The dielectric behavior observed for the polystyrene microcapsules are interpreted quantitatively in terms of the dielectric theory proposed.

Dielectric properties of moist CaCO3 filled polyethylene composites

“…The observed low frequency permittivities were higher than this value for the D62 samples, but were much lower for the other samples. One must look for the reason for these discrepancies, since the complex Bruggeman or Hanai Equation (16) proved to be successful in describing the dielectric behaviour of concentrated emulsions, including three phase systems consisting of encapsulated particles [17]. The non-Debye shape of the dielectric loss curves in the present study can arise from the electrical interactions between the filer particles.…”

Theory of dielectric relaxations due to the interfacial polarization for two-component suspensions of spheres

“…Equation (20) is, therefore, simplified to the equation which was proposed in the previous paper [3,4] for a single component suspension of j-spheres. Dielectric forumlation for this kind of concentrated suspension of shelled spheres can be achieved by introducing equivalent complex relative permittivities e~ and e~k of the shelled j-spheres and k-spheres in the same manner as used previously in the dielectric analysis ofmicrocapsules [12,13], lipid vesicles [18] and erythrocyte suspensions [19].…”

“…The frequency dependence of the permittivities and the conductivities was also discussed in detail for W/O emulsions [6,7] and suspensions of ion exchange resin gel beads in water [8][9][10][11]. Furthermore the dielectric relaxations for the concentrated suspensions of spheres covered with a shell were formulated N 105 and were successfully applied to the observations of polystyrene microcapsules [12,13].…”

Dielectric spectroscopy of single cells: time domain analysis using Maxwell's mixture equation

“…Using equations (18) and (19) in our model and expanding equations (16a) and (16b), we obtain (see details in appendix II)…”

“…The size of this dispersion is generally very small and not evident in measurements except in specific cases. For example, Zhang et al [19] measured the dielectric relaxation of polystyrene microcapsules and measured two relaxations, termed the P and Q dispersion.…”