Convection-assisted assembly of cellulose nanowhiskers embedded in an acrylic copolymer

Khelifa, Farid; Habibi, Youssef; Leclère, Philippe; Dubois, Philippe

doi:10.1039/c2nr33194b

Cited by 18 publications

(15 citation statements)

References 40 publications

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“…Alignment can be induced by applying hydrodynamic shear to a CNC suspension (Figure c) . In the isotropic phase, the average orientation of nanorods under low shear (0.5 s −1 ) is normal to the shear plane, while at high shear (500 s −1 ) it is parallel to the shear direction .…”

Section: Controlling the Alignmentmentioning

confidence: 99%

“…In the cholesteric phase, high shear disrupts the helicoidal order and leads to parallel alignment . Solid birefringent materials with nematic order can thus be produced by applying shear continuously during the evaporation process, or during fast deposition by either spin‐coating or blade‐coating . More importantly, applying moderate hydrodynamic shear to a drying suspension can lead to helicoidal nanostructures with uniform vertical alignment of the helical axis, as observed near the center of a suspension dried on a circularly oscillating plate …”

Section: Controlling the Alignmentmentioning

confidence: 99%

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The Self‐Assembly of Cellulose Nanocrystals: Hierarchical Design of Visual Appearance

et al. 2017

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By controlling the interaction of biological building blocks at the nanoscale, natural photonic nanostructures have been optimized to produce intense coloration. Inspired by such biological nanostructures, the possibility to design the visual appearance of a material by guiding the hierarchical self‐assembly of its constituent components, ideally using natural materials, is an attractive route for rationally designed, sustainable manufacturing. Within the large variety of biological building blocks, cellulose nanocrystals are one of the most promising biosourced materials, primarily for their abundance, biocompatibility, and ability to readily organize into photonic structures. Here, the mechanisms underlying the formation of iridescent, vividly colored materials from colloidal liquid crystal suspensions of cellulose nanocrystals are reviewed and recent advances in structural control over the hierarchical assembly process are reported as a toolbox for the design of sophisticated optical materials.

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Section: Controlling the Alignmentmentioning

confidence: 99%

Section: Controlling the Alignmentmentioning

confidence: 99%

The Self‐Assembly of Cellulose Nanocrystals: Hierarchical Design of Visual Appearance

et al. 2017

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“…A great variety of methods have been reported to increase surface roughness, including UV reactions [12], UV grafting [13,14], UV/ozone reactions [15,16], laser/plasma etching [17,18], chemical surface treatments [19], sequential growth of polymer layers [20,21,22], surface casting [7], and nanofiller loading [23,24,25,26]. All mentioned procedures present relative advantages and drawbacks.…”

Section: Introductionmentioning

confidence: 99%

Increased Surface Roughness in Polydimethylsiloxane Films by Physical and Chemical Methods

et al. 2017

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Two methods, the first physical and the other chemical, were investigated to modify the surface roughness of polydimethylsiloxane (PDMS) films. The physical method consisted of dispersing multi-walled carbon nanotubes (MWCNTs) and magnetic cobalt ferrites (CoFe2O4) prior to thermal cross-linking, and curing the composite system in the presence of a uniform magnetic field H. The chemical method was based on exposing the films to bromine vapours and then UV-irradiating. The characterizing techniques included scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, optical microscopy, atomic force microscopy (AFM) and magnetic force microscopy (MFM). The surface roughness was quantitatively analyzed by AFM. In the physical method, the random dispersion of MWCNTs (1% w/w) and magnetic nanoparticles (2% w/w) generated a roughness increase of about 200% (with respect to PDMS films without any treatment), but that change was 400% for films cured in the presence of H perpendicular to the surface. SEM, AFM and MFM showed that the magnetic particles always remained attached to the carbon nanotubes, and the effect on the roughness was interpreted as being due to a rupture of dispersion randomness and a possible induction of structuring in the direction of H. In the chemical method, the increase in roughness was even greater (1000%). Wells were generated with surface areas that were close to 100 μm2 and depths of up to 500 nm. The observations of AFM images and FTIR spectra were in agreement with the hypothesis of etching by Br radicals generated by UV on the polymer chains. Both methods induced important changes in the surface roughness (the chemical method generated the greatest changes due to the formation of surface wells), which are of great importance in superficial technological processes.

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“…Moreover, some publications showed that PF-QNM revealed to be a powerful tool to characterise the mechanical properties of composite materials with biopolymer in particular to characterise cellulose nanowhiskers (Khelifa et al, 2013), chitin nanorods and polymer bends (Bahrami et al, 2019). More recently, a report (Qi et al, 2019) analysed the interphase properties in carbon fibre reinforced epoxy matrix.…”

Section: Introductionmentioning

confidence: 99%

Quantitative mapping of high modulus materials at the nanoscale: comparative study between atomic force microscopy and nanoindentation

Germanicus

Mercier

Agrebi

et al. 2020

Journal of Microscopy

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Summary Local mechanical properties of submicron features are of particular interest due to their influence on macroscopic material performance and behaviour. This study is focused on local nanomechanical measurements, based on the latest Atomic Force Microscopy (AFM) mode, where the peak force set point is finely controlled at each pixel. After probe calibration, we evaluate the impact of spring constant of two AFM hand‐crafted natural full diamond tips with steel cantilevers, used for mapping. Based on the fast capture of the cantilever deflection at each pixel and real time force curve analysis in the elastic region, AFM local measured contact moduli mappings of the silica beads (>50 GPa) incorporated in an epoxy resin matrix, are compared with those determined using classical instrumented nanoindentation tests. Our analyses show that with the two AFM probes, without local residual deformation, the high moduli of the silica beads measured with this advanced AFM mode are within the standard deviation of the values determined by classical nanoindentation. Lay Description The knowledge of material properties at the nanometer scale is a key parameter for well understanding and determining the behavior of material at macroscopic scale. In this paper, we compare two methods (an advanced mode and a classical one) based on the analysis of probes in interaction with the surface of studied material. We focus on a latest developed mode for determining local mechanical properties with a very high spatial resolution. For the advanced mode, we also consider two different hand‐crafted probes. Our analyses show that with the high spatial resolution advanced mode, local mechanical properties are well determined. We also highlight the impact of the properties of the used probes for this advanced mode. In a final step, the power of the presented investigation lies in the fact that it does not modify the topography of the surface.

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Convection-assisted assembly of cellulose nanowhiskers embedded in an acrylic copolymer

Cited by 18 publications

References 40 publications

The Self‐Assembly of Cellulose Nanocrystals: Hierarchical Design of Visual Appearance

The Self‐Assembly of Cellulose Nanocrystals: Hierarchical Design of Visual Appearance

Increased Surface Roughness in Polydimethylsiloxane Films by Physical and Chemical Methods

Quantitative mapping of high modulus materials at the nanoscale: comparative study between atomic force microscopy and nanoindentation

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