Shear-induced transitions

Berrett J F, Molino F, Porte G, Diat O and Lindner P 1996 The shear-induced transition between oriented textures and layer-sliding-mediated flows in a micellar cubic crystal J. Phys. Condens Matters 9513-17... 

A. Shear-induced phase transitions in confined fluids... 

Besides shear-induced phase transitions, Uquid-gas equilibria in confined phases have been extensively studied in recent years, both experimentally [149-155] and theoretically [156-163]. For example, using a volumetric technique, Thommes et al. [149,150] have measured the excess coverage T of SF in controlled pore glasses (CPG) as a function of T along subcritical isochoric paths in bulk SF. The experimental apparatus, fully described in Ref. 149, consists of a reference cell filled with pure SF and a sorption cell containing the adsorbent in thermodynamic equilibrium with bulk SF gas at a given initial temperature T,- of the fluid in both cells. The pressure P in the reference cell and the pressure difference AP between sorption and reference cell are measured. The density of (pure) SF at T, is calculated from P via an equation of state. 

Integrating over the hysteresis loop between the compression and decompression curves in Figure 19 yields the amount of energy dissipated through the reversible bond formation/dissociation process. Unfortunately, it is not possible to determine the contribution of these transitions to the friction of phosphate films because such a calculation would require knowledge of the number of similar instabilities that occur per sliding distance, which is certainly beyond the limits of first-principles calculations. Nonetheless, the results do indicate that pressure- and shear-induced chemical reactions can contribute to the friction of materials. 

Escalante J, Gradzielski M, Mortensen K, Hoffmann H (2000) The shear induced transition of an originally undisturbed lamellar phase to a vesicle phase. Langmuir 16(23) 8653... 

X — A/T + B (where A and B are constants) however, the parameters from the fit cannot straightforwardly be interpreted on a molecular basis (Almdal et al. 1996). A transition from shear-induced order to shear-induced disorder on increasing the shear rate has recently been reported in an asymmetric PS-PI diblock in concentrated solution (Balsara and Dai 1996). The low-shear rate ordering was consistent with the suppression of fluctuations, and the high-shear rate disordering was interpreted as arising from fluctuations of the ordered (cylindrical) microstructure (Balsara and Dai 1996). 

V. M. Sadtler, M. Guely, P. Marchal, and L. Choplin, Shear-induced phase transitions in sucrose ester surfactant,./ Colloid Interface Sci., 270 (2004) 270-275. 

The mechanism we have proposed here is somewhat similar to a shear induced smectic-C like situation. Consequently, undulations should also be observed near the smectic-A-smectic-C transitions. Indeed, Johnson and Saupe [59] and later Kumar [60] report such undulations just below the transition temperature. In the same spirit Ribotta and Durand [61] report a compression induced smectic-C like situation. 

One sees in Figure 15.18 also that this spontaneous snap-off only occurs at lower flow rates. At higher flow rates, the continuous phase does not have the time to replace the oil. The droplets now become larger, and will be dragged away by the cross-flow. Also here, one sees the transition from interfacial tension-induced spontaneous snap-off towards shear-induced snap-off by the cross-flow over the membrane. 

Simeone, M., Tassieri, M., Sibillo, V, and Guido, S. 2005. Effect of sol-gel transition on shear-induced drop deformation in aqueous mixtures of gellan and kappa-carrageenan. J. Colloid Interface Sci. 281 488-494. 

Within the fluctuation-dominated region of the disordered phase of a diblock near Todt shearing can apparently induce a transition to the ordered state (Koppi et al. 1993). Cates and Milner (1989) predicted such a phenomenon, based on a shear-induced suppression of... 

In flow the challenge has been to write convincing equations that couple concentration and composition gradients to elastic stresses and the bulk flow field. When done within a two-fluid model for polymer solutions transitions in light-scattering patterns seen in experiment may be explained. Extensions to polymer blends are potential candidates as explanations of shear-induced shifts of the spinodal and biphasic islands seen experimentally. - ... 

Krishnan, K., Almdal, K., Burghardt, W.R., Lodge, T.R and Bates, RS. (2001) Shear-induced nano-macro structural transition in a polymeric bicontinuous microemulsion. Phys. Rev. Lett., 8709, 1M. 

Rehage, H., Hoffmann, H., and Wunderlich, L, A rheological switch shear induced phase transitions in aqueous surfactant solutions, Ber. Bunsenges., 90, 1071-1075 (1986). 

Mendes, E. Narayanan, J. Oda, R. Kem. F. Candau, S.J. Manohar, C. Shear-induced vesicle-to-wormlike micelle transition. J. Phys. Chem.,B 1997,101, 2256-2258. Gustafsson. J. Oradd, G. Nyden, M. Hansson, P. Almgren, M. Defective lamellar phases and micellar polymorphism in mixtures of glycerol monooleate and CTAB in aqueous solution. Langmuir 1998, 14. 4987-4996, and references therein. 

As a result of the shear flow, order parameter fluctuations in the microemulsion phase are suppressed [142]. This destabilizes the microemulsion with respect to a lamellar phase, so that for a certain temperature range the lamellar phase can be induced by applying shear. Furthermore, fluctuations in the microemulsion become very anisotropic in shear flow. In particular, the lamellar fluctuations, which appear as the transition is approached, have wave vectors concentrated near maxCz transverse to both the flow velocity and its gradient. Therefore, a shear-induced lamellar phase is expected to occur preferentially in this orientation. A more detailed analysis [142] based on model (60) shows that for small D the shift of the transition temperature, T (D), is given by... 

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