PURSE 1996

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Browsing PURSE 1996 by Author "Bandaranayake, P. W. S. K."

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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