Related Experiment Video
Updated: Dec 25, 2025

Combining Microfluidics and Microrheology to Determine Rheological Properties of Soft Matter during Repeated Phase Transitions
Published on: April 19, 2018
Thermal property and shear wave speed indicators of phase transitions in a micellar fluid
E G Sunethra K Dayavansha1, Cecille Labuda1
1Department of Physics and Astronomy, University of Mississippi, Oxford, Mississippi 38677, USA.
Abstract:
High concentration (>100 mM) wormlike micellar (WM) fluids are non-Newtonian with micelle lengths in the tens of nanometers. The viscoelastic properties of the fluid are affected by the structure and entanglement of the micelles and thus structural phase transitions can be indirectly studied using mechanical shear waves. Although these structural phase transitions have been extensively studied as a function of concentration, comparably less work is available on the temperature dependence. In this study, shear wave speeds (SWS) were studied as a function of temperature in a cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal)-based wormlike micellar fluid as an indicator of micellar structural changes. The heat capacity and thermal conductivity were also measured as these can be expected to change with structural phase transitions. Discontinuities in SWS were observed between 12 °C and 14 °C indicating the existence of a possible structural phase transition at this temperature. Gradual variation of the thermal properties was observed during controlled heating and cooling, while during autonomous heating from crystallization to fluid, a dramatic increase in both thermal properties peaking near 13.5 °C was observed.
Related Concept Videos
Phase Transitions
Phase Transitions: Melting and Freezing
Phase Changes
A substance melts or freezes at a temperature called its melting point and boils or condenses at its boiling point. These temperatures depend on pressure. High pressure favors the denser form of the substance, so typically, high pressure...
Phase Diagrams
Phase Diagram
Phase Transitions: Vaporization and Condensation

