arXiv subjects
Publications and source records attributed to Y. Tagawa.
This paper is associated with a poster winner of a 2025 American Physical Society's Division of Fluid Dynamics (DFD) Gallery of Fluid Motion Award for work presented at the DFD Gallery of Fluid Motion. The original poster is available online at the Gallery of Fluid Motion, https://gfm.aps.org/meetings/dfd-2025/692e39e5a7f805227b16fe9e
The viscoelastic behavior of liquid polymers changes depending on the microstructure of the polymer chains. To investigate the unsteady structural changes induced by polymer chain morphology under stress, we develop a simple rheo-optical technique combining a high-speed polarization camera and dripping-onto-substrate capillary breakup extensional rheometry (CaBER-DoS), which uniaxially extends and aligns the polymer along the stress direction. Using this technique, the viscoelastic behavior and birefringence field of an extending liquid polymer are simultaneously measured. Unlike the conditions that occur under shear-stress loading with a rotational rheometer, this technique provides a linear relation between birefringence and extensional stress. The measurements reflect the structural change in a flexible polymer (a mixed solution of PEO and CNCs) in the temporal evolution of the birefringence and orientation angle, which is a measure of the orientation state and coil-stretch transition of a polymer chain. Remarkably, within the elasto-capillary regime, the measured birefringence remains constant with a constant orientation state, while the Weissenberg number gradually increases, which provides experimental evidence of the coil-stretch transition of the polymer chain under constant extensional stress loading.