Multiscale flow alignment in cellulose nanocrystals controlled by surface topology

Journal article, 2026

We address how surface topology controls the multiscale flow alignment of cellulose nanocrystal (CNC) suspensions using a single in-situ experiment that combines rheology, polarized light imaging (PLI), and small-angle X-ray scattering (SAXS). Across a series of azetidinium-based dialkyl linker topologies, we resolve the propagation of alignment from the mesoscale (PLI) to the nanoscale (SAXS). While pristine CNC suspensions exhibit nearly-simultaneous onset of mesoscale birefringence and nanoscale alignment, surface-modified systems show a pronounced decoupling between these processes. In particular, the appearance of the Maltese-cross pattern in PLI systematically precedes detectable nanoscale alignment in SAXS. This is strongly dependent on linker topology. Extending the analysis beyond the Hermans parameter, S2, to higher-order anisotropy parameters and benchmarking their evolution against a generalized Maier-Saupe-type anisotropy distribution function, we show that higher-order anisotropy parameters qualitatively distinguish alignment regimes that are indistinguishable from S2 alone. The work establishes linker topology as a controlling variable for multiscale flow alignment in CNC systems and highlights the higher-order character of their alignment behavior.