Travelling colourful patterns in self-organized cellulose-based liquid crystalline structures

Pedro E S Silva,Ricardo Chagas,Susete N Fernandes,Pawel Pieranski,Robin L B Selinger,Maria Helena Godinho

doi:10.1038/s43246-021-00182-7

Abstract

Cellulose-based systems are useful for many applications. However, the issue of self-organization under non-equilibrium conditions, which is ubiquitous in living matter, has scarcely been addressed in cellulose-based materials. Here, we show that quasi-2D preparations of a lyotropic cellulose-based cholesteric mesophase display travelling colourful patterns, which are generated by a chemical reaction-diffusion mechanism being simultaneous with the evaporation of solvents at the boundaries. These patterns involve spatial and temporal variation in the amplitude and sign of the helix´s pitch. We propose a simple model, based on a reaction-diffusion mechanism, which simulates the observed spatiotemporal colour behaviour.

Highlights

Cellulose-based systems are useful for many applications
trifluoracetic acid (TFA) acts as an auto catalyst, in the esterification of free hydroxyl groups of hydroxypropyl moiety from the cellulose derivative (HPMC)
Our results demonstrate the development of travelling colourful patterns in a self-assembled lyotropic liquid crystalline system

Summary

Introduction

Cellulose-based systems are useful for many applications. the issue of selforganization under non-equilibrium conditions, which is ubiquitous in living matter, has scarcely been addressed in cellulose-based materials. Several authors mention that the hydrophilic and hydrophobic character of cellulose-based films and fibres can be changed[6,7] Another interesting characteristic of cellulosic systems is the formation of left-handed (L), right-handed (R) or achiral self-assembled structures, at different length scales[8,9,10], regardless of the cellulose chirality, which remains unchanged at the molecular level. The literature offers examples of systems that can present both helicities despite being formed by molecules with the same chirality These systems show conformational changes due to the presence of an asymmetry that can arise from the existence of defect lines[19], as in the case of fibres and jets produced from cellulosic liquid crystalline phases under shear, or from layers of materials having different mechanical properties[20]. A reaction/diffusion simulation was performed for HPMC-TFA taking into account the material boundary conditions

Methods

Results

Conclusion