"Neutron Scattering Reveals Flow-Induced Structural Transformation and Orientational Alignment in Soft Condensed Matter"
by
Prof.Guan-Rong Huang(Department of Engineering and System Science, National Tsing Hua University)
→
Asia/Taipei
L124, Physics Building (NTHU)
L124, Physics Building
NTHU
Description
The microstructural response of soft condensed matter to external fields governs macroscopic behavior such as stability, transport, and rheology. Yet, because soft aggregates access a wide range of equilibrium and non-equilibrium morphologies, quantitatively connecting field-driven structural changes to material function remains challenging.
In this talk, I will briefly review the essentials of elastic neutron scattering for probing soft matter under controlled conditions and introduce analysis tools that extract microstructural parameters directly from two-dimensional scattering patterns. Central to this approach is a spectral decomposition based on the real spherical harmonics expansion (RSHE), which enables unified, quantitative reconstruction of local strain signatures and orientational distribution functions (ODFs).
As a case study, I will examine rod-like micellar solutions under steady shear. Using small-angle neutron scattering (SANS) coupled with rheology on aqueous CTAB rod-like micelles in sodium-nitrate brine, we observe a pronounced increase in angular anisotropy in the 2D SANS patterns with increasing shear rate, without evidence of shear banding. RSHE analysis reveals concurrent strengthening of flow alignment and a systematic reduction of the mean micellar contour length. The resulting shear-rate scaling of the mean contour length agrees with predictions from first-principles analytical theory and dissipative particle dynamics simulations. Together, these results provide direct experimental evidence for flow-induced alignment and scission in rod-like micelles and establish a general framework for interpreting shear-dependent microstructural transformations from 2D neutron scattering.
Keywords: soft condensed matter; shear flow; orientational distribution function; rod-like micelles; small-angle neutron scattering; real spherical harmonics expansion
Reference:
[1] Guan-Rong Huang, Yangyang Wang, Changwoo Do, Yuya Shinohara, Takeshi Egami, Lionel Porcar, Yun Liu, and Wei-Ren Chen, Orientational Distribution Function of Aligned Elongated Molecules and
Particles Determined from Their Scattering Signature, ACS Macro Lett. 8(10), 1257 (2019).
[2] Guan-Rong Huang, Jan-Michael Y. Carrillo, Yangyang Wang, Bobby Sumpter, and Wei-Ren Chen, An Exact Inversion Method for Extracting Orientational Ordering from Small-Angle Scattering, Phys. Chem.
Chem. Phys. 23, 4120-4132 (2021).
[3] Guan-Rong Huang, Lionel Porcar, Ryan P. Murphy, Yuya Shinohara, Yangyang Wang, Jan-Michael Y. Carrillo, Bobby G. Sumpter, Chi-Huan Tung, Changwoo Do, Wei-Ren Chen, Elongated particles in flow:
Commentary on small angle scattering investigations, J. Appl. Cryst. 58, 637-658 (2025).
[4] Guan-Rong Huang, Ryan P. Murphy, Lionel Porcar, Chi-Huan Tung, Changwoo Do, Wei-Ren Chen, Scattering Insights into Shear-Induced Scission of Rodlike Micelles, J. Colloid Interface Sci. 686, 1125-
1134 (2025).
[5] Y. Koide and S. Goto, Flow-induced scission of wormlike micelles in nonionic surfactant solutions under shear flow, J. Chem. Phys. 157(8), 084903 (2022).
[6] B. O. Conchúir and A. Zaccone, Mechanism of flow-induced biomolecular and colloidal aggregate breakup, Phys. Rev. E 87(3), 032310 (2013).