Ordering of adsorbed rigid rods mediated by the Boussinesq interaction on a soft substrate

TL;DR

This paper develops a theoretical model describing how elastic substrate deformation mediates orientational ordering of surface-deposited rods, revealing a continuous isotropic-nematic phase transition influenced by substrate elasticity.

Contribution

It introduces a novel mean-field model incorporating Boussinesq elastic interactions for anisotropic rods on soft substrates, elucidating the conditions for orientational phase transitions.

Findings

Rod interactions are mediated by substrate deformation.

A continuous isotropic-nematic transition occurs.

Elastic free-energy influences ordering behavior.

Abstract

Orientational ordering driven by mechanical distortion of soft substrates plays a major role in material transformation processes such as elastocapillarity and surface anchoring. We present a theoretical model of the orientational response of anisotropic rods deposited onto a surface of a soft, elastic substrate of finite thickness. We show that anisotropic rods exhibit a continuous isotropic-nematic phase transition, driven by orientational interactions between surface deposited rods. This interaction is mediated by the deformation of the underlying elastic substrate, and is quantified by the Boussinesq solution adapted to the case of slender, surface deposited rods. From the microscopic rod-rod interactions we derive the appropriate Maier-Saupe mean-field description, which includes the Boussinesq elastic free-energy contribution due to the substrate elasticity, derive the conditions for the existence of a continuous orientational ordering transition and discuss the implication of results in the soft (bio) systems context.