Structure and transformation of tactoids in cellulose nanocrystal suspensions

Wang, Pei‐Xi; Hamad, Wadood Y.; MacLachlan, Mark J.

doi:10.1038/ncomms11515

Cited by 234 publications

(278 citation statements)

References 34 publications

Supporting

Mentioning

267

Contrasting

Order By: Relevance

“…Unaligned tactoids result in dislocation defects (Figure S4). 39 With further drying, the biphasic to liquid crystal transition concentration is reached. At this point, further movement of CNCs and CNC tactoids is kinetically arrested, and the macroscopic surface features seen in Figure 1c are formed.…”

Section: Resultsmentioning

confidence: 99%

Dielectric Characterization of Confined Water in Chiral Cellulose Nanocrystal Films

Natarajan

Emiroglu

Obrzut

et al. 2017

ACS Appl. Mater. Interfaces

View full text Add to dashboard Cite

A known deterrent to the large-scale development and use of cellulose nanocrystals (CNCs) in composite materials is their affinity for moisture, which has a profound effect on dispersion, wetting, interfacial adhesion, matrix crystallization, water uptake, and hydrothermal stability. To quantify and control the hydration and confinement of absorbed water in CNCs, we studied sulfated-CNCs neutralized with sodium cations and CNCs functionalized with less hydrophilic methyl(triphenyl)phosphonium cations. Films were cast from water suspensions at 20 °C under controlled humidity and drying rate, yielding CNC materials with distinguishably different dielectric properties and cholesteric structures. By controlling the evaporation rate, we obtained self-assembled chiral CNC films with extended uniformity, having helical modulation length (nominal pitch) tunable from 1300 to 600 nm. SEM imaging and UV–vis–NIR total reflectance spectra revealed tighter and more uniform CNC packing in films cast at slow evaporation rates or having lower surface energy when modified with phosphonium. The dielectric constant was measured by a noncontact microwave cavity perturbation method and fitted to a classical mixing model employing randomly oriented ellipsoidal water inclusions. The dielectric constant of absorbed water was found to be significantly smaller than that for free liquid indicating a limited mobility due to binding with the CNC “matrix”. In the case of hydrophilic Na-modified CNCs, a decreasing pitch led to greater anisotropy in the shape of moisture inclusions (ellipsoidal to platelet-like) and greater confinement. In contrast, the structure of hydrophobic phosphonium-modified CNC films was found to have reduced pitch, yet the shape of confined water remained predominantly spherical. These results provide a useful perspective on the current state of understanding of CNC–water interactions as well as on CNC self-assembly mechanisms. More broadly, we believe that our results are beneficial for the realization of CNC-based functional materials and composites.

show abstract

Section: Resultsmentioning

confidence: 99%

Dielectric Characterization of Confined Water in Chiral Cellulose Nanocrystal Films

Natarajan

Emiroglu

Obrzut

et al. 2017

ACS Appl. Mater. Interfaces

View full text Add to dashboard Cite

show abstract

“…[30,36,72] Moreover, the alignment of cholesteric fields under both external fields and conflicting anchoring conditions usually involves a Fréedericksz transition. The mismatch between these two tilt values indicates that other phenomena also play an important role in defining the initial alignment β i of the cholesteric domains under magnetic field.…”

Section: Nanocrystal Filmsmentioning

confidence: 99%

Controlling the Photonic Properties of Cholesteric Cellulose Nanocrystal Films with Magnets

et al. 2017

View full text Add to dashboard Cite

The self-assembly of cellulose nanocrystals is a powerful method for the fabrication of biosourced photonic films with a chiral optical response. While various techniques have been exploited to tune the optical properties of such systems, the presence of external fields has yet to be reported to significantly modify their optical properties. In this work, by using small commercial magnets (≈ 0.5-1.2 T) the orientation of the cholesteric domains is enabled to tune in suspension as they assemble into films. A detailed analysis of these films shows an unprecedented control of their angular response. This simple and yet powerful technique unlocks new possibilities in designing the visual appearance of such iridescent films, ranging from metallic to pixelated or matt textures, paving the way for the development of truly sustainable photonic pigments in coatings, cosmetics, and security labeling.

show abstract

“…[18] CNC tactoids are anisotropic microdroplets (10 to 100 mmi n diameter) showing periodic birefringent bands that are about 10 mma part (Supporting Information, Figure S1). [18] CNC tactoids are anisotropic microdroplets (10 to 100 mmi n diameter) showing periodic birefringent bands that are about 10 mma part (Supporting Information, Figure S1).…”

mentioning

confidence: 99%

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

2016

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Structure and transformation of tactoids in cellulose nanocrystal suspensions

Cited by 234 publications

References 34 publications

Dielectric Characterization of Confined Water in Chiral Cellulose Nanocrystal Films

Dielectric Characterization of Confined Water in Chiral Cellulose Nanocrystal Films

Controlling the Photonic Properties of Cholesteric Cellulose Nanocrystal Films with Magnets

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

Contact Info

Product

Resources

About