DIELECTRIC-RELAXATION SPECTROMETRY OF MIXTURES OF WATER WITH ISOPROPOXYETHANOL AND ISOBUTOXYETHANOL - COMPARISON TO UNBRANCHED POLY(ETHYLENE GLYCOL) MONOALKYL ETHERS

At 25 degrees C the complex permittivity of mixtures of water with iso propoxyethanol (i-C(3)E(1)) and isobutoxyethanol (i-C(4)E(1)) has been measured as a function of frequency v (1 MHz less than or equal to v less than or equal to 55 GHz) and mole fraction x (0 less than or equa l to x less than or equal to 1). Within the limits of experimental err or the dielectric spectra of the liquids can be represented by a. vari ety of relaxation spectral functions. At low water content (x greater than or equal to 0.4) spectral functions reflecting an unsymmetrical c ontinuous distribution of relaxation times, like the Davidson-Cole fun ction or a restricted version of the Hill function, appear to be appro priate. Below x less than or equal to 0.4 the Hill function can also b e used. The Davidson-Cole function, however, has to be complemented by an additional Debye relaxation term. These relaxation functions and t heir parameter values are compared to those for mixtures of water with unbranched C(i)E(7) chemicals and also with simple monohydric alcohol s to extract the effects resulting from steric hindrance and the influ ence of the ether group of the ethylene glycol monoalkyl ethers, respe ctively. It is particularly found that the measured spectra of the i-C (4)E(1)/H2O mixtures largely agree with those of C(4)E(1)/H2O mixtures of similar concentration. This finding indicates that dielectric rela xation of these liquids reflects molecular motions other than ultrason ic relaxation since the latter exhibits significant differences betwee n corresponding mixtures of the stereo isomers.