scholarly journals Phase separation of rigid-rod suspensions in shear flow

1999 ◽  
Vol 60 (4) ◽  
pp. 4397-4415 ◽  
Author(s):  
Peter D. Olmsted ◽  
C.-Y. David Lu
Keyword(s):  
Phase Separation ◽  
Shear Flow ◽  
Rigid Rod

Phase equilibria in solutions of rod-like particles

1956 ◽  
Vol 234 (1196) ◽  
pp. 73-89 ◽  
Keyword(s):  
Free Energy ◽  
Phase Separation ◽  
Partition Function ◽  
Colloidal Particles ◽  
Double Layers ◽  
Positive Energy ◽  
Isotropic Phase ◽  
Electric Double Layers ◽  
Rigid Rod ◽  
Anisotropic Phase

A partition function for a system of rigid rod-like particles with partial orientation about an axis is derived through the use of a modified lattice model. In the limit of perfect orientation the partition function reduces to the ideal mixing law ; for complete disorientation it corresponds to the polymer mixing law for rigid chains. A general expression is given for the free energy of mixing as a function of the mole numbers, the axis ratio of the solute particles, and a disorientation parameter. This function passes through a minimum followed by a maximum with increase in the disorientation parameter, provided the latter exceeds a critical value which is 2e for the pure solute and which increases with dilution. Assigning this parameter the value which minimizes the free energy, the chemical potentials display discontinuities a t the concentration a t which the minimum first appears. Separation into an isotropic phase and a some what more concentrated anisotropic phase arises because of the discontinuity, in confirmation of the theories of Onsager and Isihara, which treat only the second virial coefficient. Phase separation thus arises as a consequence of particle asymmetry, unassisted by an energy term . Whereas for a large-particle asymmetry both phases in equilibrium are predicted to be fairly dilute when mixing is athermal, a comparatively small positive energy of interaction causes the concentration in the anisotropic phase to increase sharply, while the concentration in the isotropic phase becomes vanishingly small. The theory offers a statistical mechanical basis for interpreting precipitation of rod-like colloidal particles with the formation of fibrillar structures such as are prominent in the fibrous proteins. The asymmetry of tobacco mosaic virus particles (with or without inclusion of their electric double layers) is insufficient alone to explain the well-known phase separation which occurs from their dilute solutions at very low ionic strengths. Higher-order interaction between electric double layers appears to be a major factor in bringing about dilute phase separation for these and other asymmetric colloidal particles bearing large charges, as was pointed out previously by Oster.

scholarly journals Phase separation of binary mixtures in shear flow: A numerical study

2000 ◽  
Vol 62 (6) ◽  
pp. 8064-8070 ◽  
Author(s):  
F. Corberi ◽  
G. Gonnella ◽  
A. Lamura
Keyword(s):  
Phase Separation ◽  
Shear Flow ◽  
Binary Mixtures ◽  
Numerical Study

scholarly journals APPLICATION OF MONTE CARLO METHOD TO PHASE SEPARATION DYNAMICS OF COMPLEX SYSTEMS

1999 ◽  
Vol 10 (08) ◽  
pp. 1513-1520 ◽  
Author(s):  
YUTAKA OKABE ◽  
TSUKASA MIYAJIMA ◽  
TOSHIRO ITO ◽  
TOSHIHIRO KAWAKATSU
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Phase Separation ◽  
Monte Carlo Method ◽  
Shear Flow ◽  
Late Stage ◽  
Microphase Separation ◽  
Anisotropic Growth ◽  
Phase Separations ◽  
Macrophase Separation

We report the application of the Monte Carlo simulation to phase separation dynamics. First, we deal with the phase separation under shear flow. The thermal effect on the phase separation is discussed, and the anisotropic growth exponents in the late stage are estimated. Next, we study the effect of surfactants on the three-component solvents. We obtain the mixture of macrophase separation and microphase separation, and investigate the dynamics of both phase separations.

Phase Separation Mechanism of Polybutadiene/Polyisoprene Blends under Oscillatory Shear Flow

2008 ◽  
Vol 41 (18) ◽  
pp. 6818-6829 ◽  
Author(s):  
Ruoyu Zhang ◽  
He Cheng ◽  
Chenggui Zhang ◽  
Tongchen Sun ◽  
Xia Dong ◽  
...  
Keyword(s):  
Phase Separation ◽  
Shear Flow ◽  
Oscillatory Shear ◽  
Separation Mechanism ◽  
Oscillatory Shear Flow ◽  
Phase Separation Mechanism

scholarly journals Phase field study on the effect of shear flow on polymer phase separation

2012 ◽  
Vol 27 ◽  
pp. 1502-1507 ◽  
Author(s):  
Yuechan Li ◽  
Rongpei Shi ◽  
Cuiping Wang ◽  
Xingjun Liu ◽  
Yunzhi Wang
Keyword(s):  
Phase Separation ◽  
Shear Flow ◽  
Field Study ◽  
Phase Field ◽  
Polymer Phase

Phase separation of liquid mixtures under shear flow

1991 ◽  
Vol 31 (1-4) ◽  
pp. 251-259 ◽  
Author(s):  
T. Baumberger ◽  
F. Perrot ◽  
D. Beysens
Keyword(s):  
Phase Separation ◽  
Shear Flow ◽  
Liquid Mixtures

scholarly journals Viscoelastic phase separation in shear flow

2004 ◽  
Vol 70 (5) ◽  
Author(s):  
Tatsuhiro Imaeda ◽  
Akira Furukawa ◽  
Akira Onuki
Keyword(s):  
Phase Separation ◽  
Shear Flow

Small-angle neutron scattering study of shear-induced phase separation in aqueous poly(N-isopropylacrylamide) solutions

e-Polymers ◽  
2004 ◽  
Vol 4 (1) ◽  
Author(s):  
Markus Stieger ◽  
Peter Lindner ◽  
Walter Richtering
Keyword(s):  
Phase Separation ◽  
Shear Flow ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Separation Process ◽  
High Shear ◽  
Shear Rates ◽  
High Shear Rates ◽  
Strong Shear ◽  
Phase Separation Process

Abstract The influence of shear flow on the structure of concentrated aqueous poly(N-isopropylacrylamide) solutions near the lower critical solution temperature was investigated by means of small-angle neutron scattering. Two samples, both in the semi-dilute regime above the overlap concentration, were studied. The scattering curve of the less concentrated sample was not influenced by shear flow, although high shear rates were reached. The more concentrated 4 wt.-% sample, however, displayed shear-induced demixing under strong shear flow conditions. Experiments at different shear stresses indicated the existence of a threshold shear stress and the phase separation process became faster with increasing stress. The two-dimensional scattering patterns remained isotropic even during the phase separation process and the correlation length as obtained from an Ornstein- Zernike plot increased. The influence of shear flow on the phase separation process is thus similar to a temperature increase. The results are in excellent agreement with data from recent rheo-optical experiments where shear-induced phase separation was also observed for the concentrated solution at high shear rates. Apparently, strong shear flow exerts an effect analogous to a temperature increase.

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