PURSE 1996

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Browsing PURSE 1996 by Author "Dissanayake, M. A. K. L."

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    Factors Affecting the In-Situ conductivity of electronically conducting Polymers
    (University of Peradeniya, Peradeniya, 1996-08-10) Vidanapathirana, K. P.; Senadeera, G. K. R.; Guanratne, L. M. W. K.; Kareem, A. M.; Dissanayake, M. A. K. L.
    In recent years the discovery of doped organic polymers with high electronic conductivities has generated substantial research interest among physicists and chemists. Conjugated polymers such as polyacetylene, polypyrrole, polythiophene, polyparaphenylene with doped derivatives reported to have conductivities larger than 1 S/cm. The films obtained in organic media exhibit superior characteristics in favour of their conductivity and mechanical properties. However, the use of organic solvent is costly and hazardous. Hence the use of water as a solvent for the polymerization is evidently advantageous. Therefore, in this study, investigations have been carried out to find the effect of pH of the electrolyte, effect of the size of the dopant ion, effect of the electrolyte concentration and the effect of the current density used in the polymerization on the in-situ conductivity of poly N methyl pyrrole in aqueous media. The polymerization current density has the largest influence on the conductivity. The conductivity increase with the decreasing current density. pH of the electrolyte also effects the conductivity. The films formed using higher acidic media seems to have high conductivity. As seen in the non aqueous media, the conductivity changes with the size of the anion and the concentration of electrolyte.
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    High Ion Conducting 3D Network Poly(Ethylene Oxide)
    (University of Peradeniya, Peradeniya, 1996-08-10) Perera, K. S.; Dissanayake, M. A. K. L.; Bandaranayake, P. W. S. K.
    Studies of ionic conductivity in polymers complexed with divalent or trivalent cations are useful for understanding the parameters related to conductivity in polymers. In the present work a calcium salt has been selected since it is less hygroscopic than corresponding alkaline salts when dissolved in poly (ethylene oxide) network. The polycondensation between ex, ro - diol-poly (ethylene glycol), H(OCH2CH2).,OH with average MW 1000 and 3-chloro-2- chloromethyl-l-propane was done in the presence of excess KOH. The average molecular weight of the linear polycondensate determined by gel permeation chromatography was about 20,000. Cross-linking of linear polycondensate was done by free-radical polymerization using dibenzoyl peroxide as initiator to obtain a thin film of 3D network polymer. Membranes of 11 mm diameter were cut from the completely dried films. To prepare samples of different O/Ca ratio, calcium trifluoromethyl-sulphonate Ca(CF3S03h salt was dissolved in a small amount of acetonitrile and the membrane was put to absorb the whole solution. It was possible to prepare sample with O/Ca ratio from 8 to 100. Then the membranes were dried under vacuum at 90°C for one day. The electrical conductivity of membranes was measured under vacuum by a complex impedance technique in the temperature range from 90°C to room temperature. The maximum conductivity was obtained for O/Ca=25 which is about 2.0 x }O"4 S em" at 75°C and 1.0 x 10.5 S em" at room temperature. Polymers synthesized in this method have glass transition temperatures below room temperature and hence, give a very high ionic conductivity and have very good mechanical properties due to three dimensional link