Effect of temporary network structure on linear and nonlinear viscoelasticity of polymer solutions

Abstract

We investigated the effects of temporary network structures on linear and nonlinear viscoelasticity of polymer solutions by use of oscillatory shear (LAOS) flow. We tested two different types of polymer solutions: entanglement systems and ion complex systems. It was found that the entanglement network is difficult to show shear-thickening while network of ion complex gives rise to shear-thickening. The objectives of this paper are the test of strain-frequency superposition for various polymer solutions and to suggest a new method classifying complex fluids consisting temporary networks using LAOS data.

The Method of Harmonic Balance for the Giesekus Model under Oscillatory Shear

“…Eqn. (29), which describes the pattern of convergence for such systems, can be adapted for our system using equations ( 35), ( 36) and ( 37) with y = [N 1 , N 2 , σ 12 ] T and…”

“…As γ 0 and ω increase, the behavior becomes increasingly nonlinear. Such large amplitude oscillatory shear (LAOS) measurements have been extensively used to study rheological phenomena including shear thinning/thickening and strain softening/hardening [1,2,3,4], timedependent structural buildup or breakage [5,6,7,8,9,10], pseudoplasticity and elastoviscoplasticity [11,12,8], shear banding [13,14,15,16], wall slip [17,18,19,20], gelation [21,22,23,24], chain stretch and entanglement in polymeric systems [25,26,27,28,29,30], etc. Several analytical approaches have been introduced to interpret experimental LAOS data including Fourier series [31], power series [32], Pade approximants [33], Chebyshev polynomi-als [34], stress decomposition methods [35,36], characterstic waveforms [19], weakly nonlinear intrinsic parameters [37], sequence of physical processes [38], etc.…”