Title: Exploring Calorimetry under Steady Shear – Construction and Measurements
Institut Néel, Room E424 (Louis Weil)
Abstract: In this presentation, I will introduce our recent attempt to perform calorimetry under controlled shear flow. Measuring intrinsic thermodynamic quantities under non-equilibrium conditions is experimentally challenging, because shear generates additional heat. To address this issue, we developed a differential scanning calorimeter equipped with a shearing system (Shear-DSC). A key technical challenge was to quantitatively separate shear-induced heating from transition-related heat flow, allowing us to extract intrinsic thermal signals. Using this system, we investigated shear-induced transitions in the liquid crystal (8CB) and in an aqueous surfactant (CTAB) solution. Under shear, the smectic–nematic transition of 8CB broadened and shifted slightly to lower temperatures, whereas the nematic–isotropic transition was nearly unaffected. In the CTAB system, the crystal-to-rodlike micellar transition depended on shear rate, reflecting fragmentation of crystallites and orientational ordering of rod-like micelles. Interestingly, despite clear structural changes, the changes in transition entropy remained relatively small in both systems. These results suggest that shear modifies mesoscopic ordering without drastically altering the underlying thermodynamic landscape.
