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  • 1
    Electronic Resource
    Electronic Resource
    Dielectric observations on polystyrene microcapsules and the theoretical analysis with reference to interfacial polarization (1983)
    Springer
    Colloid & polymer science 261 (1983), S. 381-389 
    Details
    ISSN: 1435-1536
    Keywords: Conductivity ; Dielectric property ; Dielectric relaxation ; Interfacial polarization ; Microcapsule ; Permittivity ; Polystyrene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Dielectric measurements were carried out for polystyrene microcapsules which were prepared by means of an interfacial polymer deposition technique. The microcapsules showed a couple of dielectric relaxations termedP for lower andQ 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 relaxationsP andQ 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01418210
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  • 2
    Electronic Resource
    Electronic Resource
    Dielectric study of poly(methyl methacrylate) microcapsules in particular reference to the effect of the frequency dependence of the permittivity of the capsule wall (1986)
    Springer
    Colloid & polymer science 264 (1986), S. 943-950 
    Details
    ISSN: 1435-1536
    Keywords: Dielectric property ; interfacial polarization ; microcapsule ; poly(methylmethacrylate) ; polystyrene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The dielectric behavior of poly(methyl methacrylate) (PMMA) microcapsules was analyzed theoretically by taking account of the frequency dependence of the relative permittivityɛ s and the electrical conductivityχ s of the capsule wall. For comparison, similar analysis was applied to polystyrene (PS) microcapsules which have frequency-independentɛ s andχ s . The behavior ofɛ s andχ s of the PMMA microcapsules was assumed to be represented by a dielectric relaxation of them-th power type on the basis of dielectric data on underwater PMMA films. By means of a theory of the interfacial polarization, some consideration was carried out regarding the effect of the frequency dependence ofɛ s andχ s on the dielectric behavior of the PMMA microcapsules. The consideration led to predictions that the frequency dependence ofɛ s andχ s causes (i) the variation in the relaxation intensity with the change in the conductivity of suspending medium, (ii) the frequency dependence of the permittivity at low frequencies and (iii) the frequency dependence of the conductivity at high frequencies. The theoretical prediction (i) was verified by observed data, (ii) and (iii) remaining unverified owing to the experimental difficulty.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01410859
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  • 3
    Electronic Resource
    Electronic Resource
    Dielectric approach to polystyrene microcapsule analysis and the application to the capsule permeability to potassium chloride (1984)
    Springer
    Colloid & polymer science 262 (1984), S. 513-520 
    Details
    ISSN: 1435-1536
    Keywords: Dielectric property ; dielectric relaxation ; microcapsule ; permittivity ; polystyrene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A method of numerical analysis is proposed to determine the phase parameters from dielectric observations of polystyrene microcapsules by using the conductivity at intermediate frequencies between two dielectric relaxations observed. The method was more feasible for the analysis of the microcapsule observations than the method by which the calculation is performed by use of the permittivity at lower frequencies. The method was applied to the dielectric observations of the KCl-loaded microcapsules to obtain the permittivity and the conductivity of the capsule interior, the thickness of the capsule wall, the volume fraction of the suspended capsules and the conductivity of the surrounding aqueous phase. The conductivity of capsule interior was found to be unchanged with time for as long as 3 months. From the results it is concluded that the microcapsules are impermeable to KCl.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01451514
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