A method for determination of the complex dielectric permittivity of polar, non‐polar and ion‐containing polymers at microwave frequencies is presented. Disk‐shaped samples are employed in a radial‐line configuration at the end of a coaxial‐line structure. An equivalent circuit, established by admittance measurements, is used to relate the capacitance at the sample face to the impedance measured on the slotted line preceding the coaxial sample holder. The method has been applied first to determine the frequency spectrum of polyethylene (PE) and poly(tetrafluoroethylene) (PTFE) between 80 MHz and 4 GHz at 293 K. The results agree with those reported in the literature, demonstrating the reliability of the method as well as usability of PE and PTFE as standards at high frequencies. Subsequently, the AMF C‐311 cation exchange membrane (polyfluorocarbon backbone chains with grafted polystyrene side chains containing sulfonate groups) was studied in the same frequency range. Values of dielectric permittivity and dielectric losses for AMF C‐311 samples in the dry and swollen hydrated states are reported and compared.

Derivatograph was used to investigate pseudohomogeneous ion-exchange membranes. Two membrane types were examined: a) a membrane obtained from polyethylene film modified with the copolymer of styrene and DVB; and b) membrane AMF C-311 obtained on a film of fluorinated polymeric material.Although differential thermal analysis (DTA) has been used in the investigation of polymers only recently, a large number of papers concerning different problems in this field have already appeared. Only a few of these papers, however, have been devoted to cross-linked polyelectrolytes and more exclusively to ion-exchange resins [1-5], i.e. "homogeneous" polyelectrolytes. Up to date no publication dealing with "pseudohomogeneous" ion-exchange membranes has appeared. The pseudohomogeneous membrane is a system of two phases: a polymer film (polyethylene is most often used as matrix), with a cross-linked acid (e.g.polystyrenesulphonic acid) dispersed in the polymer film. The present investigation was undertaken to find the correlation between the thermal curves of a pseudohomogeneous cation-exchange membrane and the thermal properties of both phases of the membrane. ExperimentalTwo types of these membranes were examined: a) a membrane obtained from polyethylene film modified with the copolymer of styrene and DVB; this membrane was synthesized at Wroctaw Polytechnic School; b) membrane AMF C-311 (American Machine and Foundry Co.) obtained on a film of fluorinated polymeric material.The examination of other polymers was performed to explain endo-and exothermic effects occurring in the DTA curves of pseudohomogeneous ion-exchange membranes. These polymers were: the initial polyethylene film (PE); the polyethylene film modified with the copolymer of styrene and DVB (before sulphonation); the ethylene-styrene copolymer; the PE and PS homopolymer physical mixture; and the mixture of PE and polystyrenesulphonic acid ion-exchangers with different degrees of cross-linking.13"

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