Shear-DSC study on the crystal-isotropic phase transition of semidilute aqueous cetyltrimethylammonium bromide (CTAB) solutions

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作   者：

Yamamoto T.;  Wakabayashi T.;  Kamiyama T.;  Suzuki H.; 

作者机构：

Department of Chemistry Kindai University; 

关键词：

Rod-like micelle;  Shear-induced changes;  Crystal-to-isotropic transition;  Shear differential scanning calorimetry (Shear-DSC);  Aqueous cetyltrimethylammonium bromide (CTAB) solution; 

期刊名称：

Thermochimica Acta: An International Journal Concerned with the Broader Aspects of Thermochemistry and Its Applications to Chemical Problems

i s s n：

0040-6031

年卷期：

2023 年 730 卷

页   码：

摘   要：

© 2023 Elsevier B.V.A differential scanning calorimeter equipped with a steady shear flow system (Shear-DSC) was developed, and the effects of shearing on the crystal-isotropic phase transition were investigated for aqueous cetyltrimethylammonium bromide (CTAB) solutions at 4, 18, and 26 wt%. At 18 wt%, where rod-like micelles are formed in the isotropic phase, the transition temperature Ttrs changes with the shear rate γ˙. At low shear rate (γ˙<1s−1), Ttrs decreases as γ˙ increases due to an increase in the surface energy of the crystal grains. At high shear rate (γ˙>30s−1), Ttrs increases as γ˙ increases because of the orientational ordering of rod-like micelles induced by shearing in the isotropic phase, leading to the formation of a nematic structure. The latter change is suppressed for the solution at 26 wt% because the nematic phase is formed without shearing, whereas it disappears at 4 wt% indicating that the spherical micelles are not deformed by shearing.