Dynamically controlled iridescence of cellulose ...
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Twisted, Luxembourg 10-12 May 2016 Dynamically controlled iridescence of cellulose nanocrystal assemblies with electric field Bruno Frka-Petesic, 1,2 Bruno Jean, 1 Laurent Heux*, 1 1 CERMAV-CNRS, Grenoble, France; 2 Melville laboratory, Dept. of Chemistry, University of Cambridge, Cambridge, UK Natural structures are often made of hierarchically organized assemblies of nanometric elements, with precise functions, like the helicoids in the iridescent beetle shells. Cellulose nanocrystals (CNCs), isolated e.g. by sulphuric acid hydrolysis from cellulosic fibers, are one of the typical model of chiral nanorods with dimensions of 2-50 nm in diameter for up to several microns in length depending on their biological origin [1]. When dispersed in apolar solvents using surfactants, CNCs spontaneously phase- separate into chiral nematic structures, but at much higher concentrations than in those already observed in aqueous media. The chiral pitch decreases to a few microns, revealing a stronger chiral interaction [2] and beautiful iridescent colors in suspension. Additionally, CNCs can be oriented by relatively modest electric fields [3]. Recently, we also showed that these colloids bear a permanent dipole as high as 4000 Debye [4]. Combining this orientation features with the self-organization properties, we showed that it is not only possible to orient the cholesteric domains, but also to unwind the cholesteric axis to any desired pitch value as shown by laser light diffraction and iridescence. These spectacular features allow the controlled production of iridescent substrate with tailored properties, and even a dynamical control of the orientation. References [1] S. Elazzouzi, Y. Nishiyama, J.-L. Putaux, L. Heux, et al. Biomac., 9, 57–65, 2008 [2] D. Bordel, J.-L. Putaux, and L. Heux Langmuir, 22, 4899–4901, 2006 [3] S. Elazzouzi, J.-L. Putaux and L. Heux J. Phys. Chem. B, 113,11069–11075, 2009 [4] B. Frka-Petesic, B. Jean and L. Heux, Europhysic Letters[1], 107 28006 2014 [5] B. Frka-Petesic, H. Radavidson, B. Jean & L. Heux Adv. Mater.,: 10.1002 2017 1 a) Iridescence p/2 p/2 p/2 p 0 /2 p 0 /2 p/2 Cholesteric behaviour 1 b) Laser light diffraction 1 cm E AC Laser 2θ’ θ 1 θ 3 Green Red θ 2 Blue
Transcript of Dynamically controlled iridescence of cellulose ...
Twisted,Luxembourg 10-12May2016
Dynamicallycontrollediridescenceofcellulosenanocrystalassemblieswithelectricfield
Bruno Frka-Petesic,1,2 Bruno Jean,1 Laurent Heux*,1 1CERMAV-CNRS, Grenoble, France;
2 Melville laboratory, Dept. of Chemistry, University of Cambridge, Cambridge, UK
Naturalstructuresareoftenmadeofhierarchicallyorganizedassembliesofnanometricelements, with precise functions, like the helicoids in the iridescent beetle shells.Cellulosenanocrystals(CNCs),isolatede.g.bysulphuricacidhydrolysisfromcellulosicfibers,areoneof the typicalmodelofchiralnanorodswithdimensionsof2-50nm indiameter for up to severalmicrons in lengthdependingon their biological origin [1].When dispersed in apolar solvents using surfactants, CNCs spontaneously phase-separateintochiralnematicstructures,butatmuchhigherconcentrationsthaninthosealready observed in aqueous media. The chiral pitch decreases to a few microns,revealingastrongerchiralinteraction[2]andbeautifuliridescentcolorsinsuspension.
Additionally,CNCscanbeorientedbyrelativelymodestelectricfields[3].Recently,wealso showed that these colloids bear a permanent dipole as high as 4000 Debye [4].Combining this orientation featureswith the self-organization properties,we showedthat it is not only possible to orient the cholesteric domains, but also to unwind thecholesteric axis to any desired pitch value as shown by laser light diffraction andiridescence. These spectacular features allow the controlled production of iridescentsubstratewithtailoredproperties,andevenadynamicalcontroloftheorientation.
References[1]S.Elazzouzi,Y.Nishiyama,J.-L.Putaux,L.Heux,etal.Biomac.,9,57–65,2008[2]D.Bordel,J.-L.Putaux,andL.HeuxLangmuir,22,4899–4901,2006[3]S.Elazzouzi,J.-L.PutauxandL.HeuxJ.Phys.Chem.B,113,11069–11075,2009[4]B.Frka-Petesic,B.JeanandL.Heux,EurophysicLetters[1],107280062014[5]B.Frka-Petesic,H.Radavidson,B.Jean&L.HeuxAdv.Mater.,:10.10022017
1a)Iridescence
p/2 p/2 p/2p0/2p0/2
p/2
Cholestericbehaviour
1b)Laserlightdiffraction
1cm
EAC
Laser2θ’
θ1
θ3 GreenRed
θ2 Blue
