Playing the blues, the greens and the reds with cellulose-based structural colours

Chagas, Ricardo; Silva, Pedro E. S.; Fernandes, Susete N.; Žumer, S.; Godinho, M. H.

doi:10.1039/d0fd00020e

Cited by 8 publications

(8 citation statements)

References 32 publications

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“…Evaporation drives the diffusion of the two solvents from inside of the quasi-2D samples to the outside. We recall that in previous work with 1D systems (flat capillaries) similar diffusion toward the two menisci was observed 32 . For the same interval of time, the colours of the quasi-2D samples change significatively during the first 8 days, unlike the precursor L-handed solutions in vials.…”

Section: Resultssupporting

confidence: 65%

“…The observed behaviour cannot however be attributed solely to the diffusion of the solvent. The chemical reaction that can occur between the TFA and the cellulosic chain must also play a crucial role, as was identified for the 1D geometry and other cellulosic systems 11,32 . One of the products that results from the chemical esterification of HPMC is water.…”

Section: Resultsmentioning

confidence: 93%

“…Lyotropic solutions in the vials. One of the routes to induce the inversion of the helix handedness, in a cellulose-based lyotropic system, is the use of reactive solvents 12,32 . In this study, room temperature reaction between solutions of TFA and HPMC yields iridescent colours that vary with the HPMC concentration (see Supplementary Movie 1 and Supplementary Fig.…”

Section: Resultsmentioning

confidence: 99%

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

et al. 2021

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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.

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Section: Resultssupporting

confidence: 65%

Section: Resultsmentioning

confidence: 93%

Section: Resultsmentioning

confidence: 99%

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

et al. 2021

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“…, , To explain the reverse of the handedness of the chiral nematic supramolecular helicoidal structure a conformational self-arrangement of the cellulosic chain was considered [23]. Similar behaviour was observed for samples encapsulated in capillaries [32].…”

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confidence: 75%

Colourful Patterns in Cellulose-Based Liquid Crystals

Silva¹,

Rosa²,

Chagas³

et al. 2021

Liq. Cryst. and their Appl.

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Cellulose-based thermotropic and lyotropic liquid crystals can be obtained from macromolecules or colloidal particles, such as cellulose nanocrystals. Thermotropic liquid crystals are produced by the effect of temperature, while lyotropic liquid crystals occur in solution for a given range of concentration, pressure, and temperature. Cellulose liquid crystals can form chiral nematic phases characterized by Bragg-type reflections of circularly polarized light. This characteristic is related to a helical structure formed by pseudo nematic layers twisted around an optical axis. The helical structure is characterized by the values of pitch and helicity. The later can be right-(R) or left-(L) handed. Cellulose liquid crystals are well described in literature. They are a source of materials for many applications, including the production of photonic chiral materials. Although many questions remain unanswered such as the origin of helicity of cellulosic chiral structures and those related to out-ofequilibrium systems. In this paper, we are focused at the out-of-equilibrium systems obtained from lyotropic cellulose-based liquid crystals. The development of colorful patterns involving the pitch variation in space and time of self-organized cellulose cholesteric structures is revised.

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“…CNC suspensions have related optical properties because of their chiral nematic structure, 17 which can be retained in CNC films and results in a structured color after the water evaporates 18,19 . Many studies have shown that by changing the magnetic field intensity, 20 the starting concentration, 21 the solvent, 22,23 the evaporation rate, 24 the evaporation temperature, 25 the particle size, 26,27 the surface charge, 28 and the ionic strength of the liquid, 29 the pitch can be manipulated to adjust the structure color of the film. With a safe and stable structural color, CNCs can be modified or combined with other compounds to prepare light, heat, pH, humidity, or gas sensitive films 30–35 .…”

Section: Introductionmentioning

confidence: 99%

The preparation of cellulose nanocrystal/1,3‐butylene glycol composite structural color films and humidity‐responsive

Wang

Meng

et al. 2022

J of Applied Polymer Sci

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Cellulose nanocrystals (CNCs) can self‐assemble in an aqueous solution to form a chiral nematic liquid crystal structure, which is maintained in the subsequent solid iridescent film and presents a unique structural color. In this study, in order to explore the effect of ultrasound on the optical properties of CNC, CNC films with a chiral nematic helix structure and different structural colors were prepared by ultrasonic‐assisted dispersion and natural static evaporation. Results showed that prolonging the ultrasonic duration significantly increased layer pitches and red‐shifted the color of CNC films, likely due to increased steric hindrance and a larger electric double layer. On this basis, CNC/1,3‐butylene glycol (BG) composite films were prepared with uniform and structural color. Results showed that BG was incorporated into CNCs most likely through hydrogen bonds. Moreover, the presence of BG increased the layer pitches and red‐shifted the structural color of CNC/BG composite films, which indicates that structural color of the film has a good stability response to humidity. On the whole, our work provides a new point of view in understanding the role of ultrasound and small‐molecule additives in the preparation of CNC‐based films.

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Playing the blues, the greens and the reds with cellulose-based structural colours

Abstract: Structural vivid colours can arise from the interference of light reflected from structures exhibiting periodicity on scales in the range of visible wavelengths. This effect is observed with light reflected...

Cited by 8 publications

References 32 publications

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

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

Colourful Patterns in Cellulose-Based Liquid Crystals

The preparation of cellulose nanocrystal/1,3‐butylene glycol composite structural color films and humidity‐responsive

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