Leveraging a Hyperbolic Nozzle Geometry to Induce Nanostructure Alignment in Elastomeric Block Copolymers

Abstract

This study investigates the effect of nozzle geometry on flow-induced nanostructure alignment in a 50 wt% Pluronic 84 and water solution using birefringence imaging. The original objective was to evaluate alignment behavior in SEBS (styrene-ethylene-butylene-styrene) block copolymers under 3D printing conditions. However, mechanical failure of the 3D-printed nozzles—cracking under the high pressures— necessitated a pivot in material and methodology. Pluronic 84 was selected as a model system. Two nozzle geometries—a conical and a hyperbolic profile—were evaluated across a wide range of flow rates. While the hyperbolic nozzle was expected to induce greater alignment due to smoother extensional flow, both geometries produced comparable alignment levels. This suggests that the highly structured and viscoelastic nature of the Pluronic gel may limit further alignment regardless of flow profile. Instabilities observed in the birefringence images, potentially caused by elastic flow behavior or sample inhomogeneities were further investigated using non-polarized imaging. These findings highlight the interplay between flow geometry and material properties in directing nanostructure orientation. Future work will revisit SEBS with stronger nozzle materials and explore a wider range of pluronic concentrations, and nozzle geometries.