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Multidimensional Helical Nanostructures in Multiscale Nanochannels
Lee, Sunhee,Kim, Hanim,Tsai, Ethan,Richardson, Jacqueline M.,Korblova, Eva,Walba, David M.,Clark, Noel A.,Lee, Sang Bok,Yoon, Dong Ki American Chemical Society 2015 Langmuir Vol.31 No.29
<P>We have investigated the various morphological changes of helical nanofilament (HNF; B4) phases in multiscale nanochannels made of porous anodic aluminum oxide (AAO) film. Single or multihelical structures could be manipulated depending on the AAO pore size and the higher-temperature phase of each molecule. Furthermore, the nanostructures of HNFs affected by the chemical affinity between the molecule and surface were drastically controlled in surface-modified nanochannels. These well-controlled hierarchical helical structures that have multidimensions can be a promising tool for the manipulation of chiral pores or the nonlinear optical applications.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/langd5/2015/langd5.2015.31.issue-29/acs.langmuir.5b01620/production/images/medium/la-2015-01620z_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/la5b01620'>ACS Electronic Supporting Info</A></P>
Multistep hierarchical self-assembly of chiral nanopore arrays
Kim, Hanim,Lee, Sunhee,Shin, Tae Joo,Korblova, Eva,Walba, David M.,Clark, Noel A.,Lee, Sang Bok,Yoon, Dong Ki National Academy of Sciences 2014 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.111 No.40
<P><B>Significance</B></P><P>Bent-core mesogenic molecules form smectic liquid crystal phases in which the molecular layers are locally polar and chiral, and have a built-in tendency for saddle splay curvature, a combination that fills bulk neat bent-core smectics with self-assembled helical nanofilament bundles of twisted layers. This observation led us to explore the growth mode of such smectics under conditions of nanoconfinement and the remarkable observation reported here that single nanofilaments readily grow in linear nanoscale pores, generating a new motif of hierarchically self-assembled hybrid organic/inorganic structures for applications in chiral synthesis and separation.</P><P>A series of simple hierarchical self-assembly steps achieve self-organization from the centimeter to the subnanometer-length scales in the form of square-centimeter arrays of linear nanopores, each one having a single chiral helical nanofilament of large internal surface area and interfacial interactions based on chiral crystalline molecular arrangements.</P>
Self-assembled hydrophobic surface generated from a helical nanofilament (B4) liquid crystal phase
Kim, Hanim,Yi, Youngwoo,Chen, Dong,Korblova, Eva,Walba, David M.,Clark, Noel A.,Yoon, Dong Ki The Royal Society of Chemistry 2013 Soft matter Vol.9 No.10
<P>Hydrophobic air/liquid crystal (LC) surfaces exhibiting self-assembled dual scale roughness have been made by simple cooling of a bent-core mesogen from its high temperature isotropic melt through two liquid crystal phases. The transition to the fluid smectic B2 phase generates micron-scale toric focal conic domains (TFCDs) at the surface. Upon further cooling into the hexatic smectic B4 phase these TFCD structures are preserved and become textured by the nanometer-sized helical nanofilaments (HNFs) of the B4. The resulting TFCD/HNF surface is hydrophobic and shows clear evidence for surface tension reduction characteristic of dual-scale roughness, suggesting a simple self-assembly-based approach to low surface tension surfaces using LC morphology.</P> <P>Graphic Abstract</P><P>Hydrophobic air/liquid crystal (LC) surfaces exhibiting self-assembled dual scale roughness have been made by simple cooling of a bent-core mesogen from its high temperature isotropic melt through two liquid crystal phases. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3sm27221d'> </P>
Ryu, Seong Ho,Shin, Tae Joo,Gong, Tao,Shen, Yongqiang,Korblova, Eva,Shao, Renfan,Walba, David M,Clark, Noel A,Yoon, Dong Ki Published by the American Physical Society through 2014 Physical review. E, Statistical, nonlinear, and so Vol.89 No.3
<P>We have identified a metastable liquid-crystal (LC) structure in the de Vries smectic-A* phase (de Vries Sm-A*) formed by silicon-containing molecules under certain boundary conditions. The phase transition with the metastable structure was observed in a LC droplet placed on a planar aligned substrate and LCs confined in the groove of a silicon microchannel. During the rapid cooling step, a batonnet structure was generated as an intermediate and metastable state prior to the transition that yielded the thermodynamically stable toric focal conic domains. This distinctive behavior was characterized using depolarized reflection light microscopy and grazing incidence x-ray diffraction techniques. We concluded that the silicon groups in the molecules that formed the de Vries phase induced the formation of layered clusters called cybotactic structures. This observation is relevant to an exploration of the physical properties of cybotactic de Vries phases and gives a hint as to their optoelectronic applications.</P>