Viscoelasticity of polymer-thickened water-in-oil emulsions
Alejandro Peña, Alberto Montesi, George Hirasaki, and Matteo Pasquali
Chemical Engineering Department, Rice University, Houston, TX 77005
Monday     4:50     Judiciary (Track 3)

The rheological behavior of a set of emulsions of water dispersed in lubricant oil and stabilized with a nonionic surfactant (SPAN 80, 5% wt.) was determined in steady and sinusoidal oscillatory shear tests. For each water concentration, emulsions were tested with and without adding to the oil phase polyisobutylene (PIB, MW = 2.1 ± 0.2 x 10⁶ Mg/mol) at the overlap concentration (0.5% wt.). The distribution of drop sizes of each emulsion was determined via NMR.

The steady shear viscosity of the emulsions grew noticeably with water content, and was affected significantly less by the presence of polymer. Similarly, the elastic and viscous moduli and related linear viscoelastic properties were affected mainly by the dispersed phase content, and not by the presence of PIB in the oil. These findings are explained in terms of the effects of the population and distribution of droplets and the ability of the drops to deform under shear.

A constitutive model for nematic polymers with elastic anisotropy
Jimmy Feng
City College of CUNY, Levich Institute, New York, NY 10031
Monday     1:30     Diplomat/Ambassador (Track 4)

Gel is an elastic object swollen by solvent, so the force acting on the gel is coupled with the diffusion of the solvent. The stress-diffusion coupling is seen commonly in everyday life (water coming out of squeezed gel) and is also important in many chemical engineering processes, soaking, drying and sedimentation. The stress diffusion coupling is also important in the study of artificial muscles, where the deformation of the gel is controlled by electric field. Here I propose basic equations for the stress diffusion coupling for ionic gel, and discuss some strange electro-chemical effect found recently in Nafion gels.

Dynamics of gels in flow and electric field
Masao Doi
Department of Computational Science and Engineering, Nagoya University, Nagoya, Japan
Tuesday     8:30     Crystal Ballroom (Plenary Lectures)

Gel is an elastic object swollen by solvent, so the force acting on the gel is coupled with the diffusion of the solvent. The stress-diffusion coupling is seen commonly in everyday life (water coming out of squeezed gel) and is also important in many chemical engineering processes, soaking, drying and sedimentation. The stress diffusion coupling is also important in the study of artificial muscles, where the deformation of the gel is controlled by electric field. Here I propose basic equations for the stress diffusion coupling for ionic gel, and discuss some strange electro-chemical effect found recently in Nafion gels.

The nature of the divergence in the low shear viscosity of dispersions of hard spheres
Zhengdong Cheng¹, Jixiang Zhu², Paul Chaikin³, See-Eng Phan⁴, and William B. Russel^5
1Dicon Fiberoptics, Inc., Richmond, CA; ²Correlator.com, Bridgewater, NJ 08807; ³Department of Physics, Princeton University, Princeton, NJ 08544; ⁴Applied Materials, San Jose, CA 95129; ⁵Department of Chemical Engineering, Princeton University, Princeton, NJ 08544-5263
Tuesday     9:45     Cabinet (Track 1)

Measurements of the low shear viscosity h₀ with a Zimm-Crothers viscometer for dispersions of colloidal hard-spheres are reported as a function of volume fraction f up to 0.56. The relative viscosity h₀/m is correlated over a wide range of volume fractions by the Doolittle and Adam-Gibbs equations, indicating an exponential divergence at f_m = 0.640±0.004. Non-equilibrium theories based on solutions to the two-particle Smoluchoski equation or ideal mode coupling approximations do not capture the divergence. The data extends the previously proposed master curve, providing a test for improved theories for the many-body thermodynamic and hydrodynamic interactions that determine the viscosity of hard sphere dispersions.

Julia A. Kornfield¹, Charles S. Nickerson¹, Giyoong Tae¹, Mary Dickinson¹, Angelique Louie¹, Robert Lambert², Hampar Karageozian², John Park³, Kathryn A. Rich⁴, and Vincent Monnier^5
1Department of Chemical Engineering, California Institute of Technology, Pasadena, CA 91125; ²ISTA Pharmaceuticals, Irvine, CA; ³Consultant, Irvine, CA; ⁴Huntington Medical Research Institute, Pasadena, CA; ⁵Case Western Reserve University, Cleveland, OH