Dielectric properties of hydrated or dehydrated ionic gels

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A system for the dielectric measurement has been made. The system is well designed to controll the temperature and to shield the electric wave during the measurement. A cell adapting to the gel has been developed. The dielectric spectra in the frequency range between 0.1Hz and 1MHz are obtained when the conductance of test sample is less than 1uS.The polymer gels of N-isopropylacrylamide, into which a small amount of ionic styrensulfonate(0.5mo1%: NIPA-SS5 ; 0.1mo1% : NIPA-SS1 ; Omo1%: NIPA)is introduced, have been synthesized and their dielectric properties have been examined by using the measuring system mentioned above. The temperature dependence of diffusion coefficients of small ions in the gel has been examined by using the method which we have developed(Bull. Chem. Soc. Jpn., 69, 2173-2178(1996)). From these measurements, the followings have been clarified. 1)The diffusion coefficient of small ion in the collapsing NIPA gel is one hundredth of that in the swelling gel. 2)The conductance of the collapsing gel is also about one hundredth of the swelling gel. 3)The dielectric dispersions are observed in the low(10Hz-100Hz)and high (1MHz)frequency regions for any of NIPA NIPA-SS5 gels in the collapsing state. 4)The NIPA=SS1 and NIPA-SS5 gels in the swelling state exhibit the dispersions around 0.2MHz but the NIPA gel in the swelling state doesn't. These results strongly indicate that the water molecules in the collapsing gels are electrically disconnected or disperse as isolated clusters(like the water molecules in oil). The result of 3)suggests that the strong ion-pair forms between the ionic group on the gel chain and the counter ion in the collapsing gels and that the relaxation frequency of structured water in the hydrated state is between 10Hz and 100Hz. These results have been published as a full paper and a part of them has been submitted.