Flexible Mesoporous Photonic Resins with Tunable Chiral Nematic Structures

Khan, Mostofa K.; Giese, Michael; Yu, Marcus; Kelly, Joel A.; Hamad, Wadood Y.; MacLachlan, Mark J.

doi:10.1002/anie.201303829

Cited by 159 publications

(115 citation statements)

References 33 publications

(56 reference statements)

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“…These photonic films have immediate application potential in many photonic materials and devices, e.g., in security papers for anti-counterfeiting purposes (Tabor et al, 2012), sensors (Giese et al, 2013a;Zhang et al, 2013), or in mirrorless lasing (Lagerwall et al, 2014;Wenzlik et al, 2014). Further enhancements are possible by letting the liquid crystalline order organize guest nanoparticles Liu et al, 2014;Nguyen et al, 2014;Querejeta-Fernandez et al, 2014) or template an inorganic or other organic phase that is synthesized within the polysaccharide suspension (Shopsowitz et al, 2010(Shopsowitz et al, , 2012a(Shopsowitz et al, ,b, 2014Kelly et al, 2012;Giese et al, 2013b;Khan et al, 2013). The self-assembled N* order also holds potential for creating extremely strong, yet light-weight composites, mimicking the helical internal structure of the most performing biocomposites found in Nature.…”

Section: Introductionmentioning

confidence: 99%

Equilibrium Liquid Crystal Phase Diagrams and Detection of Kinetic Arrest in Cellulose Nanocrystal Suspensions

et al. 2016

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The cholesteric liquid crystal self-assembly of water-suspended cellulose nanocrystal (CNC) into a helical arrangement was observed already more than 20 years ago, and the phenomenon was used to produce iridescent solid films by evaporating the solvent or via sol-gel processing. Yet, it remains challenging to produce optically uniform films and to control the pitch reproducibly, reflecting the complexity of the three-stage drying process that is followed in preparing the films. An equilibrium liquid crystal phase formation stage is followed by a non-equilibrium kinetic arrest, which in turn is followed by structural collapse as the remaining solvent is evaporated. Here, we focus on the first of these stages, combining a set of systematic rheology and polarizing optics experiments with computer simulations to establish a detailed phase diagram of aqueous CNC suspensions with two different values of the surface charge, up to the concentration where kinetic arrest sets in. We also study the effect of varying ionic strength of the solvent. Within the cholesteric phase regime, we measure the equilibrium helical pitch as a function of the same parameters. We report a hitherto unnoticed change in character of the isotropic-cholesteric transition at increasing ionic strength, with a continuous weakening of the first-order character up to the point where phase coexistence is difficult to detect macroscopically due to substantial critical fluctuations.

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Section: Introductionmentioning

confidence: 99%

Equilibrium Liquid Crystal Phase Diagrams and Detection of Kinetic Arrest in Cellulose Nanocrystal Suspensions

et al. 2016

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“…[4] Despite growing interest in solid chiral particles,t here are still few examples of these materials. [6] Above ac ritical concentration, aqueous suspensions of CNCs spontaneously form ac hiral nematic (cholesteric) liquid-crystalline phase, [7] which has been applied for templating silica, [8] carbon, [9] and polymers [10] with long-range chiral nematic structures.T ypically,CNCs dispersed in water or other solvents are mixed with the precursors of silica or polymers and, after an evaporation-induced self-assembly (EISA) process,c omposite materials with chiral nematic order are obtained. [6] Above ac ritical concentration, aqueous suspensions of CNCs spontaneously form ac hiral nematic (cholesteric) liquid-crystalline phase, [7] which has been applied for templating silica, [8] carbon, [9] and polymers [10] with long-range chiral nematic structures.T ypically,CNCs dispersed in water or other solvents are mixed with the precursors of silica or polymers and, after an evaporation-induced self-assembly (EISA) process,c omposite materials with chiral nematic order are obtained.…”

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confidence: 99%

Polymer and Mesoporous Silica Microspheres with Chiral Nematic Order from Cellulose Nanocrystals

2016

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Polymer microspheres with chiral nematic order were obtained from an emulsion polymerization technique using cellulose nanocrystals (CNCs) as the template. The growth of the liquid crystals from tiny tactoids to droplets with spherical symmetry was captured and investigated by both optical and electron microscopy for the first time. The size of the microspheres could be tuned between tens and hundreds of micrometers; to obtain single, integrated chiral nematic kernels, the size of water droplets in the emulsion should be similar to that of CNC tactoids. Through a double-matrix templating method, novel silica microspheres with chiral nematic order were fabricated, which showed a high surface area and mesoporosity. The methods developed here may help to reveal the evolution of other self-assembling systems, and these materials have potential applications in optical devices and chiral separations.

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“…The coloration of the resins was controlled not only by addition of salt to the initial suspension but also by application of external pressure on the resins. Furthermore, flexible mesoporous phenol-formaldehyde resins with iridescent color were produced by removing CNC entities from chiral nematic CNC/phenol-formaldehyde composites through alkaline treatment at high temperatures (e.g., 70 C) [128]. CNC removal resulted in a blue shift of the iridescent color, probably as a result of the decrease in pitch following volume shrinkage, in addition to the lowered refractive index as a porous material.…”

Section: Polymer Composites With Liquid Crystalline Cncsmentioning

confidence: 99%

Liquid Crystals of Cellulosics: Fascinating Ordered Structures for the Design of Functional Material Systems

Nishio

Sato

Sugimura

2015

Advances in Polymer Science

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This article surveys progress in both fundamental and applied research related to cellulosic liquid crystals, mainly of chiral nematic order. These liquid crystals are divided into two different classes, namely cellulosic macromolecules and cellulose nanocrystals (CNCs), depending on the mesogenic constituent. We start with a review of the fundamental and chiroptical characteristics of molecular liquid crystals of representative cellulose derivatives and then discuss recent efforts on the design and construction of functional material systems (such as stimulisensitive optical media and novel hybrids with minerals). These systems make use of the liquid crystalline molecular assembly of cellulosics. The survey of the other class of cellulosic liquid crystals deals with colloidal suspensions of CNCs obtained by acid hydrolysis of native cellulose fibers. Following the review of fundamental aspects related to the isotropic-anisotropic phase separation behavior of CNC suspensions, attention is directed to current applications of free-standing colored films, polymer composites reinforced with CNCs as mesofiller, and inorganic hybridizations using CNC chiral nematics as template. Some comments and the outlook for future explorations are also offered.

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Flexible Mesoporous Photonic Resins with Tunable Chiral Nematic Structures

Cited by 159 publications

References 33 publications

Equilibrium Liquid Crystal Phase Diagrams and Detection of Kinetic Arrest in Cellulose Nanocrystal Suspensions

Equilibrium Liquid Crystal Phase Diagrams and Detection of Kinetic Arrest in Cellulose Nanocrystal Suspensions

Polymer and Mesoporous Silica Microspheres with Chiral Nematic Order from Cellulose Nanocrystals

Liquid Crystals of Cellulosics: Fascinating Ordered Structures for the Design of Functional Material Systems

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