Orientation and dynamics of stiff polymeric nanoparticles

TL;DR

This paper presents an experimental method to characterize the orientation dynamics of nanorod suspensions, advancing understanding of nanoscale mechanisms for their assembly into hierarchical structures.

Contribution

It introduces a birefringence relaxation technique to quantify nanorod orientation dynamics, linking rotational diffusion to particle size and flow conditions.

Findings

Birefringence relaxation effectively measures nanorod orientation.

Rotational diffusion coefficients depend on particle size distributions.

Flow-induced orientation mechanisms are elucidated for nanocelluloses.

Abstract

Successful assembly of suspended nanoscale rod-like particles depends on fundamental phenomena controlling rotational and translational diffusion. Despite the significant developments in fluidic fabrication of nanostructured materials, the ability to quantify the dynamics in processing systems remains challenging. Here we demonstrate an experimental method for characterization of the orientation dynamics of nanorod suspensions in assembly flows using birefringence relaxation. The methodology is illustrated using nanocelluloses (cellulose nanocrystals and nanofibrils) as model systems, where the coupling of rotational diffusion coefficients to particle size distributions as well as flow-induced orientation mechanisms are elucidated. Our observations advance the knowledge on key fundamental nanoscale mechanisms governing the dynamics of nanotubes and nanorods allowing bottom-up assembly into hierarchical superstructures.