Optical birefringence in uniaxially compressed aerogels

Bhupathi, P.; Jaworski, Lukas M.; Hwang, Jungseek; Tanner, D. B.; Obukhov, Sergei; Lee, Y; Mulders, N.

doi:10.1088/1367-2630/12/10/103016

Cited by 16 publications

(24 citation statements)

References 35 publications

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“…In a typical birefringent material that has one optical axis, the transmitting polarized light intensities measured between crossed and parallel polarizers can be described by Eqs. (1)–(3) that depend on the orientation of the optical axis (i.e., the stretching direction of CNC-E in this study), where d is sample thickness, λ is wavelength, R is retardation, θ is angle, and Δ n is birefringence 31 .The spectra from stretched CNC-E fit well to the theoretical spectra at a given film thickness (Supplementary Figure 8). Moreover, birefringence estimation obtained from polarized UV-vis spectroscopy revealed a gradual increase of birefringence as CNC-E was elongated (Fig.…”

Section: Resultssupporting

confidence: 58%

Unwinding a spiral of cellulose nanocrystals for stimuli-responsive stretchable optics

et al. 2019

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Cellulose nanocrystals (CNCs) derived from biomass spontaneously organize into a helical arrangement, termed a chiral nematic structure. This structure mimics the organization of chitin found in the exoskeletons of arthropods, where it contributes to their remarkable mechanical strength. Here, we demonstrate a photonic sensory mechanism based on the reversible unwinding of chiral nematic CNCs embedded in an elastomer, leading the materials to display stimuli-responsive stretchable optics. Vivid interference colors appear as the film is stretched and disappear when the elastomer returns to its original shape. This reversible optical effect is caused by a mechanically-induced transition of the CNCs between a chiral nematic and pseudo-nematic arrangement.

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Section: Resultssupporting

confidence: 58%

Unwinding a spiral of cellulose nanocrystals for stimuli-responsive stretchable optics

et al. 2019

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“…It is known that incompressible rubber‐like materials have ν = 0.5 while the most compressible materials have ν = –1. Assuming that the aerogel disk is uniformly expanded in a radial direction under uniaxial compression, the ν values of rGO and x‐rGO were measured to be 0.09 and 0.03 at 30% strain, respectively. Taking into consideration that the ν value of graphene ranges from 0.16 to 0.23, the compressibilities of both aerogels are substantially enhanced due to the interconnecting networked porous structure .…”

Section: Resultsmentioning

confidence: 99%

Reversibly Compressible, Highly Elastic, and Durable Graphene Aerogels for Energy Storage Devices under Limiting Conditions

Hong

Bak

Wie

et al. 2014

Adv Funct Materials

155

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High porosity combined with mechanical durability in conductive materials is in high demand for special applications in energy storage under limiting conditions, and it is fundamentally important for establishing a relationship between the structure/chemistry of these materials and their properties. Herein, polymer-assisted self-assembly and cross-linking are combined for reduced graphene oxide (rGO)-based aerogels with reversible compressibility, high elasticity, and extreme durability. The strong interplay of crosslinked rGO (x-rGO) aerogels results in high porosity and low density due to the re-stacking inhibition and steric hinderance of the polymer chains, yet it makes mechanical durability and structural bicontinuity possible even under compressive strains because of the coupling of directional x-rGO networks with polymer viscoelasticity. The x-rGO aerogels retain >140% and >1400% increases in the gravimetric and volumetric capacitances, respectively, at 90% compressive strain, showing reversible change and stability of the volumetric capacitance under both static and dynamic compressions; this makes them applicable to energy storage devices whose volume and mass must be limited.

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“…The examination of molecular anisotropy is based on the fact that a linearly polarized incident light beam travelling through a uniaxially oriented material is split into two orthogonally polarized rays (ordinary and extraordinary rays) with different phase velocities so that a phase difference (d) can be identified between the rays emerging from the material (Bhupathi et al 2010). If a light beam with intensity of I 0 is incident on an anisotropic material which is placed between two crossed polarizers, the transmitted light intensity I can be given by Eq.…”

Section: Polarized Optical Microscopy (Pom)mentioning

confidence: 99%

Toughening mechanisms in cellulose nanopaper: the contribution of amorphous regions

Mao

Meng

et al. 2017

Cellulose

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Cellulose nanopaper is a strong and tough fibrous network composed of hydrogen bonded cellulose nanofibres. Upon loading, cellulose nanopaper exhibits a long inelastic portion of the stress-strain curve which imparts high toughness into the material. Toughening mechanisms in cellulose nanopaper have been studied in the past but mechanisms proposed were often rather speculative. In this paper, we aim to study potential toughening mechanisms in a systematic manner at multiple hierarchical levels in cellulose nanopaper. It was proposed that the toughness of cellulose nanopaper is not, as is often assumed, entirely caused by large scale inter-fibre slippage and reorientation of cellulose nanofibres. Here it is suggested that dominant toughening mechanism in cellulose nanopaper is associated with segmental motion of molecules facilitated by the breakage of hydrogen bonds within amorphous regions .

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Optical birefringence in uniaxially compressed aerogels

Cited by 16 publications

References 35 publications

Unwinding a spiral of cellulose nanocrystals for stimuli-responsive stretchable optics

Unwinding a spiral of cellulose nanocrystals for stimuli-responsive stretchable optics

Reversibly Compressible, Highly Elastic, and Durable Graphene Aerogels for Energy Storage Devices under Limiting Conditions

Toughening mechanisms in cellulose nanopaper: the contribution of amorphous regions

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