Diffusivity in 2-butoxyethanol/water mixtures of noncritical composition approaching the liquid/liquid coexistence curve

Abstract

Results of dynamic light scattering experiments are reported which demonstrate that the mutual diffusion coefficient of 2-butoxyethanol/water mixtures of noncritical composition exhibits a characteristic temperature and composition dependence: The diffusion coefficients of the two phases of noncritical composition coexisting along the liquid/liquid coexistence curve decrease by an order of magnitude in the temperature range (Tp−Tc)<10 K approaching the lower critical point (Tp, temperature of phase separation; Tc, critical temperature). In the homogeneous 1-fluid phase region of the phase diagram, the D vs (T−Tp) curves of mixtures of noncritical composition are shifted to smaller values of D with decreasing values of ‖y−yc‖ (y, mass fraction of 2-butoxyethanol; yc, critical mass fraction). These findings are discussed on the basis of the model of regular mixtures.

Slowing Down of the Mutual Diffusion Process Approaching the Liquid/Liquid Coexistence Curve of a Nonionic Surfactant/Deuterium Oxide System: Study of the System C12E5/D2O

“…It is well established that the slowing down of the mutual diffusion process approaching the liquid/liquid coexistence curve of systems with a miscibility gap is a system independent phenomenon. [1][2][3][4][5] The data shown in Figure 4 are replotted in the form of isotherms in the upper part of Figure 5 to bring out similarities to results reported by Kato et al for the same system 30 The critical temperature of the system C 12 E 5 /water is about 20 K lower than that of the system C 12 E 6 /water. In the system C 12 E 6 /water Strey et al have carried out temperature jump experiments to study the dynamics of the system.…”

“…The sample with the composition y ) 2.0 × 10 -2 was prepared from a C12E5 stock different from that from which the other samples were prepared. (1) …”

“…Several runs were made to improve the statistics of the photon counts. g (2) (t) was converted into the normalized first-order electric field time correlation function g (1) (t) using the relation (g (1) (1) (t) and A(Γ i ) are related by a Laplace transform given by eq 1.…”

Composition fluctuations in a non-critical binary polymer blend studied by ultrasonic and light scattering experiments

“…The gas-liquid transition of one-component systems 33 and the phase behaviour of low molecular weight binary mixtures [17][18][19][20][21]34,35 can be described satisfactorily in the frame of the empirical pseudospinodal concept.…”

“…) and polypropylene glycol (M ¼ 1000 g mol À1 ) can be interpreted by the dynamic scaling theory for low molecular weight binary critical mixtures of Bhattacharjee and Ferrell. 11 Although there are some light scattering [17][18][19][20][21] and ultrasonic 22 measurements of non-critical low molecular weight mixtures, to our knowledge no measurements of the composition fluctuations of non-critical polymer mixtures by ultrasonic attenuation or light scattering have been reported so far.…”