Nonlinear Viscoelastic Behavior of Aqueous Hybrid Threadlike Micellar Solutions

Abstract

Nonlinear viscoelastic behavior of aqueous hybrid threadlike micellar solutions consisting of cetyltrimethylammonium bromide (CTAB) and sodium poly(styrene-ran-sodium styrenesulfonate) (P(St/NaSS)) in water was investigated. Strain-hardening behavior well described with a three-(freely jointed)-chain model was observed when start-up shear flows at shear rates sufficiently higher than the reciprocal of the longest relaxation times were applied to the solutions. The size of segments, which is a reasonable measure of rigidity of hybrid threadlike micelles, evaluated from the number of segments necessary to make the best fit curves to shear stresses with the three-chain model were greater than that of the ordinary threadlike micelles consisting of CTAB and a low molar mass compound, sodium p-toluenesulfonate, possessing similar molecular structure to the monomer of P(St/NaSS). Moreover, the molar mass of segments was independent of the molar mass of incorporated P(St/NaSS)s in the hybrid threadlike micelles.

Viscoelastic Behavior of Aqueous Solutions of Charged Hybrid Threadlike Micelles

“…[21][22][23][24] We recently reported that some aqueous HTM systems also showed strain-hardening behavior. 25) However, strain-hardening behavior has been merely observed in the concentrated polymer systems, which only show shear-thinning behavior. According to Inoue et al, 23,24) the mechanism of strain-hardening behavior is attributed to the finite extensibility of the threadlike micelles forming fused temporal cross-linking between two threadlike micelles at entanglement points.…”