Concentration fluctuations shear-induced

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). 

J. van Egmond and G.G. Fuller, Time dependent small angle light scattering of shear-induced concentration fluctuations in polymer solutions, J. of Chem. Physics, 96, 7742 (1992). 

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... 

Endoh, M. K., M. Takenaka, T. Inoue, H. Watanabe, and T. Hashimoto. 2008. Shear small-angle light scattering studies of shear-induced concentration fluctuations and steady state viscoelastic properties.. Chem. Phys. 128 Article 164911. 

Diffusive dynamics described by theTDGL, CDS, and DDFT methods can be used if the kinetic pathway toward eqiulibrium is important. It is assumed that the inertia term is negligible compared to the other forces. The physical reason for this is that the viscous environment of the chain hinders fast accelerations of the maaomolecules. However, the results should be analyzed with caution since diffusive dynamics does not induce a resistance associated with fluid viscosity in the presence of an external driving force, does not take into account drain entanglements, and finally, does not indude hydrodynamic and dastic stress couplings, which are often important. As a result, polymer-spedfic kinetic processes, such as viscodastic phase separation and shear enhancement of concentration fluctuations, cannot be studied. Note also that... 

Fig. 5 Regions of shear-induced enhancement of concentration fluctuations, A/c < 0. for G = 2, according to the CM model. Reproduced with permission from reference [60]...

Figure 3 Changes in steady-state scattering patterns with increasing shear rate. The change from pattern (a) to (b) indicates shear-induced homogenization or singie-phase formation, and that from pattern (c) to (d) indicates shear-induced phase-separation or concentration fluctuations. The arrow indicates the fiow direction (x-axis) and the bar corresponds to the scattering angle 0= 7° in the solutions. The arrow and the bar are common to all the patterns. Based on Hashimoto, T. In Soft Matter Characterization Borsali, R., Pecora, R., Eds. Springer New York, 2008 Vol. 1, Chapter 8, pp 378-462. ...

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