Frequency dependent linear viscoelastic properties of ordered polystyrene latices

Abstract

An experimental investigation of linear rheological properties of monodisperse ordered latex dispersions has been carried out. Measurements of the dynamic shear modulus and the dynamic viscosity in the frequency range between 0.04 Hz and 2500 Hz are reported. The volume fraction and the electrolyte concentration were variables in the experiment. The results show that a description of the rheological behaviour with a simple linear phenomenological equation is not possible. The measured dynamic moduli can only be described with a great number of relaxation times.

Hard sphere colloidal dispersions: Mechanical relaxation pertaining to thermodynamic forces

“…The linear viscoelastic behaviour of a system which is purely viscous for co --* 0 and viscoelastic for co --+ oo [6] figure 1 the results are shown together with the theoretical predictions. The first conclusion which can be drawn is that more than one relaxation time is present (as expected); this is evident from the asymmetry of t/" as a function of co. Further it is observed that the measurements for a = 2 8 n m and a = 76nm roughly coincide.…”

“…For reasons of simplicity the calculations involve only the two-body distribution function which at equilibrium (superscript 0) is related to the radial distribution function g (r) by p0 (xi, x2) = n 2 g (r) (6) where n is the number density and r = ]x 1 -x2].…”

“…A better understanding of dispersions, which are rheologically extremely complex, can be obtained from theoretical and experimental studies in which one or more of the following aspects dominate: strong Van der Waals interactions [1], elasticity of long range electrostatic repulsions [2][3][4][5][6], and long range steric interaction in suspensions at volume fraction approaching closest packing [7][8][9]. In hard sphere suspensions hydrodynamic, Brownian and hard sphere interactions [10,11] dominate, whereas in emulsions interface effects are important [12,13].…”

Hydrodynamic and Colloidal Interactions in Concentrated Charge-Stabilized Polymer Dispersions

“…The radial distribution function g(r ) appearing in Eq. [7] depends on the surface potential of the particles, which greatly complicates a rigorous inversion of Eq. [7] to obtain the pair potential from G ∞ measurements.…”

“…The relationship between the high-frequency modulus and the interaction potential is deduced from the well-known Zwanzig and Mountain formula [7] neglecting hydrodynamic interactions (51),…”