References of "Park, Ji Hyun"
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See detailMacroscopic control of helix orientation in films dried from cholesteric liquid crystalline cellulose nanocrystal suspensions

Park, Ji Hyun; Noh, Junghyun UL; Schütz, Christina et al

in Chemphyschem : A European Journal of Chemical Physics and Physical Chemistry (2014), 15(7), 1477-1484

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 ... [more ▼]

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. [less ▲]

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See detailCellulose nanocrystal-based materials: from liquid crystal self-assembly and glass formation to multifunctional thin films
Lagerwall, Jan UL; Schütz, Christina; Salajkova, Michaela et al

in NPG Asia Materials (2014), 6(1), 80

Cellulose nanocrystals (CNCs), produced by the acid hydrolysis of wood, cotton or other cellulose-rich sources, constitute a renewable nanosized raw material with a broad range of envisaged uses: for ... [more ▼]

Cellulose nanocrystals (CNCs), produced by the acid hydrolysis of wood, cotton or other cellulose-rich sources, constitute a renewable nanosized raw material with a broad range of envisaged uses: for example, in composites, cosmetics and medical devices. The intriguing ability of CNCs to self-organize into a chiral nematic (cholesteric) liquid crystal phase with a helical arrangement has attracted significant interest, resulting in much research effort, as this arrangement gives dried CNC films a photonic band gap. The films thus acquire attractive optical properties, creating possibilities for use in applications such as security papers and mirrorless lasing. In this critical review, we discuss the sensitive balance between glass formation and liquid crystal self-assembly that governs the formation of the desired helical structure. We show that several as yet unclarified observations—some constituting severe obstacles for applications of CNCs—may result from competition between the two phenomena. Moreover, by comparison with the corresponding self-assembly processes of other rod-like nanoparticles, for example, carbon nanotubes and fd virus particles, we outline how further liquid crystal ordering phenomena may be expected from CNCs if the suspension parameters can be better controlled. Alternative interpretations of some unexpected phenomena are provided, and topics for future research are identified, as are new potential application strategies. [less ▲]

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See detailUtilizing the Krafft phenomenon to generate ideal micelle-free surfactant-stabilized nanoparticle suspensions
Dölle, Sarah; Lechner, Bob-Dan; Park, Ji Hyun et al

in Angewandte Chemie International Edition (2012), 51(13), 3254-3257

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