Anisotropic Diffusion of Nanorods within Entangled Polymer Network and Gel

Non-spherical nanoparticles exhibit direction-dependent diffusion, which can become anisotropic in crowded polymer solutions and crosslinked gels. Understanding how particle shape and aspect ratio influence motion in such environments is important to understand transport in soft and biological materials. We investigate the role of anisotropy by tracking gold nanorods (AuNRs) with varying aspect ratios dispersed in synthetic polymer networks and gel. Using Fluorescence Correlation Spectroscopy (FCS), we separately resolve the translational and rotational diffusion of individual AuNRs. The results show that rotational motion is strongly hindered, reflecting the underlying network topology and dynamic heterogeneity. These findings demonstrate how particle shape couples to microstructural constraints in complex fluids and provide a framework for using anisotropic probes to map nanoscale viscoelasticity and mesh structure.