Phase Equilibrium and Rheology of Solutions of RigidRod Polyelectrolytes.
Abstract
The purpose of this work is to study the electrical effects on the equilibrium and flow behavior of solutions of rigid rodlike polyelectrolytes. A general introduction is given in chapter 1. Electrophoresis, sedimentation and rheology of dilute suspensions of charged rods are examined in chapters 2 and 3. Phase equilibrium and rheology of solutions in liquid crystalline regime are investigated in chapters 4 and 5. The electrophoretic translational and rotational velocities of a fiber are determined in the limit L/d {>}{>}1 and lambda /d{>}{>}1, where lambda is the double layer thickness and L and d are the rod length and diameter. A nonuniformly charged fiber with a net charge dipole rotates until it becomes aligned with the electric field. The effect of deformation of the ion cloud on the translational and rotational velocity of a fiber settling due to gravity is also determined. If the fiber possesses both a net charge and a charge dipole, it will rotate into a vertical alignment in which the end with the largest absolute charge is on top. The transition from an isotropic to a nematic phase in a solution of uniformlycharged rodlike polymers is studied for weak electrostatic interactions, i.e. rm w^'=Q^2lambda/( varepsilon k_{B}TL^2) {<}{<} 1. Here Q is the total charge, varepsilon is the dielectric constant, rm k_{B} is the Boltzmann constant and T is the absolute temperature. A DebyeHuckellike theory is developed to take account of manyrod effects. Manybody correlations within the region d/lambda {<}{<} w^' {<} {<} lambda/L decreases the importance of the anisotropic electrostatic interactions and prevent a transition to a highly aligned nematic phase predicted by the second virial approximation. For w ^' {>}{>} d/lambda and w^' {>}{>} lambda/L, the anisotropic electrostatic interactions do become important and bring about a highly aligned nematic phase. The rheology of nematics of charged rods subject to simple shear flow is studied for w^' {> }{>} d/lambda and w^' {>}{> } lambda/L. For highly aligned nematics, the period of director tumbling is the same as that for a fiber orbiting in Jeffery orbits provided that the reciprocal of the angular spread is treated as an effective aspect ratio. The director can either rotates to the shearing plane or vorticity axis, depending on the initial orientation of the director.
 Publication:

Ph.D. Thesis
 Pub Date:
 1996
 Bibcode:
 1996PhDT........31C
 Keywords:

 Engineering: Chemical; Physics: Fluid and Plasma; Chemistry: Physical