Grafted Rods: A Tilting Phase Transition

TL;DR

This paper predicts a tilting phase transition in grafted rod systems driven by grafting density, balancing van-der-Waals attraction and bending elasticity, with implications for understanding surface-anchored molecular assemblies.

Contribution

It introduces a theoretical model predicting a density-controlled tilting transition for grafted rods, incorporating energetic competition and temperature effects.

Findings

Transition occurs at a critical grafting density.

Tilt favored by van-der-Waals attraction.

Opposed by bending elasticity.

Abstract

A tilting phase transition is predicted for systems comprising rod like molecules which are irreversibly grafted to a flat surface, so that the non interacting rods are perpendicularly oriented. The transition is controlled by the grafting density $\rho$. It occurs as $\rho$ increases as a result of the interplay between two energies. Tilt is favoured by the van-der-Waals attraction between the rods. It is opposed by the bending elasticity of the grafting functionality. The role of temperature is discussed, and the tilting mechanism is compared to other tilting transitions reported in the literature.