| Co-Investigator(Kenkyū-buntansha) |
WATANABE Hiroshi Kyoto University, Institute for Chemical Research, Professor, 化学研究所, 教授 (90167164)
MATSUMIYA Yumi Kyoto University, Institute for Chemical Research, Instructor, 化学研究所, 助手 (00378853)
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| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2006: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2005: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Research Abstract |
Nonlinear rheology of aqueous solutions of cetyltrimethylammonium bromide (CTAB) and sodium calicylate (NaSal) were investigated in order to study the finite extensionability of thread-like micelles and the shear induced structure. The concentration of CTAB was fixed at 0.1 mol l^<-1>, and the concentration of NaSal was varied from 0.07 to 0.4 mol l^<-1>. For all test solutions, dynamic moduli were described with the Maxwell model having a single relaxation time, τ. Time evolutions of the shear stress, σ, and the first normal stress difference, N_1, after inception of the steady shear flow were measured. For solutions having low NaSal concentrations, strain-hardening was observed and σ and N_1 diverged at a certain strain when the shear rate, γ, exceeded τ^<-1>. For solutions with high NaSal concentrations, stress overshoot similar to that of ordinary entangled polymer solutions was observed at ^between τ^<-1> and a certain critical rate, γc, while the strain-hardening was observed at γ > γc. A simple relationship for elastic solids, N_1/σ= γ with γbeing the strain imposed by shear flow, held for all the solutions in the strain-hardening regime. The strain-hardening was attributable to the strain dependent shear modulus and well described with the network theory considering finite extensibility of network strands.
In nonlinear rheological measurements, we found that the rheological data significantly depend on the material of cone-plate fixture. Strain hardening behavior measured with glassy cone-plate fixtures was remarkably weakened. Therefore, we examined the effect of surface treatments of glassy cone-plate fixtures. We found that hydrophobic treatments is quite effective to observe hardening behavior of the thread-like micelle solutions. Shear induced structure observed after cession of shear flow was found to depend on the surface treatments.
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