TAILIEUCHUNG - Hydrodynamics Advanced Topics Part 8

Tham khảo tài liệu 'hydrodynamics advanced topics part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 196 Hydrodynamics - Advanced Topics AV BkTĩ kT 24 Since the Frenkel hole theory and the Hilderbrand treatment of solvent viscosity were developed for regular solutions Anderton and Kauffman 1994 Equation 24 may not be a valid measure of the free space per solvent molecule for associative solvents like alcohols and polyalcohols. Hence for alcohols AV is calculated using dV Vm-Vs 25 where Vm is the solvent molar volume divided by the Avogadro number. Dielectric friction theories The simple description of hydrodynamic friction arising out of viscosity of the solvent becomes inadequate when the motion concerning rotations of polar and charged solutes desired to be explained. A polar molecule rotating in a polar solvent experiences hindrance due to dielectric friction DF in addition to the mechanical T or hydrodynamic friction. In general the dielectric and mechanical contributions to the friction are not separable as they are linked due to electrohydrodynamic coupling Hubbard and Onsager 1977 Hubbard 1978 Dote et al. 1981 Felderhof 1983 Alavi et al. 1991c Kumar and Maroncelli 2000 . Despite this nonseparability it is common to assume that the total friction experienced by the probe molecule is the sum of mechanical and dielectric friction components . ClM Cm Cdf 26 Mechanical friction can be modeled using both hydrodynamic Debye 1929 and quasihydrodynamic Gierer and Wirtz 1953 Dote et al. 1981 theories whereas dielectric friction is modeled using continuum theories. The earliest research into dielectric effects on molecular rotation took place in the theoretical arena. Initial investigations were closely intertwined with the theories of dielectric dispersion in pure solvents Titulaer and Deutch 1974 Bottcher and Bordewijk 1978 Cole 1984 . Beginning with the first paper to relate the dielectric friction to rotational motion published by Nee and Zwanzig in 1970 a number of studies have made improvements to the Nee-Zwanzig approach Tjai et al 1974 Hubbard and .

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