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Macroscopic Control of Helix Orientation in Films Dried from Cholesteric Liquid‐Crystalline Cellulose Nanocrystal Suspensions
Author(s) -
Park Ji Hyun,
Noh JungHyun,
Schütz Christina,
SalazarAlvarez German,
Scalia Giusy,
Bergström Lennart,
Lagerwall Jan P. F.
Publication year - 2014
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201400062
Subject(s) - materials science , helix (gastropod) , liquid crystal , cholesteric liquid crystal , nanocrystal , suspension (topology) , cellulose , optical microscope , crystallography , phase (matter) , nanotechnology , chemical engineering , chemical physics , scanning electron microscope , composite material , chemistry , optoelectronics , organic chemistry , ecology , mathematics , homotopy , snail , pure mathematics , engineering , biology
The intrinsic ability of cellulose nanocrystals (CNCs) to self‐organize into films and bulk materials with helical order in a cholesteric liquid crystal is scientifically intriguing and potentially important for the production of renewable multifunctional materials with attractive optical properties. A major obstacle, however, has been the lack of control of helix direction, which results in a defect‐rich, mosaic‐like domain structure. Herein, a method for guiding the helix during film formation is introduced, which yields dramatically improved uniformity, as confirmed by using polarizing optical and scanning electron microscopy. By raising the CNC concentration in the initial suspension to the fully liquid crystalline range, a vertical helix orientation is promoted, as directed by the macroscopic phase boundaries. Further control of the helix orientation is achieved by subjecting the suspension to a circular shear flow during drying.