Alterations in Conformations of Poly(3-hexylthiophene) on Au(111) Induced by Annealing

TL;DR

This study uses microscopy to explore how annealing affects the conformations of P3HT polymers on Au(111), revealing substrate topography and thermal energy as key control parameters for nanostructure design.

Contribution

It demonstrates how annealing and substrate reconstruction influence polymer conformations, offering a mechanistic framework for designing polymer nanostructures.

Findings

Annealing enables polymers to overcome surface energy barriers and adopt low-energy conformations.

On regular surfaces, polymers replicate the substrate's herringbone pattern.

On irregular surfaces, polymers exhibit diverse conformations and form clusters after annealing.

Abstract

Employing high-vacuum electrospray deposition and scanning tunneling microscopy, we investigated how individual poly(3-hexylthiophene) (P3HT) chains navigated on the periodic energy landscape of a reconstructed Au(111) surface. The resulting polymer conformations were governed by the interplay between the periodically corrugated substrate, in particular the depth and regularity of the modulated surface potential, and thermal energy. On a regularly reconstructed surface, annealing at {\deg}C provided sufficient energy for chain segments to overcome energy barriers of the corrugated surface potential landscape, allowing monomers along the chain to experience a strong thermodynamic driving force toward the low-energy valleys on the surface. The adsorbed polymers adopted a state where the polymer conformations were replicating the herringbone pattern. By contrast, on an irregularly reconstructed surface, the correspondingly disordered potential landscape yielded a diverse mix of coiled polymer chains performing a two-dimensional random walk and collapsed chains located in troughs of the energy landscape. Intriguingly, annealing at {\deg}C forced polymers to form clusters of many chains. Our results establish that thermal energy and substrate topography represent control parameters for altering polymer conformations, providing a mechanistic framework for rationally designing polymer nanostructures at the molecular level.