Correlation between structural properties and iridescent colors of cellulose nanocrystalline films
We investigate the effect of shear flow applied during the drying of aqueous suspension of cellulose nanocrystals on optical reflective properties and structural characteristics of the resulting solidified films. Shear flow can significantly improve internal structural homogeneity of the films, while its effect on optical reflective properties is relatively minor. The measured width of the selective reflection peak is an order of magnitude larger than expected for an ideal helically modulated structure, which reflects a distribution of pitch values and possibly also of regimes of distorted helical modulation. We attribute these imperfections to the broad size distribution of the cellulose nanocrystals.
KeywordsCellulose nanocrystals Chiral nematic liquid crystal Iridescent films Shear stress Optical reflectance spectroscopy Scanning electron microscopy
ML, BM and IDO acknowledge financial support in the frame of the National Research Program of Slovenia P1-0192. LB and CS acknowledge the Wallenberg Wood Science Center (WWSC) for financial support. CS thanks the Research Foundation – Flanders (FWO) for funding under the Odysseus Grant (G.0C60.13N).
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