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Lagerwall, J.P.F.,Scalia, G. Elsevier 2012 Current Applied Physics Vol.12 No.6
Liquid crystals constitute a fascinating class of soft condensed matter characterized by the counterintuitive combination of fluidity and long-range order. Today they are best known for their exceptionally successful application in flat panel displays, but they actually exhibit a plethora of unique and attractive properties that offer tremendous potential for fundamental science as well as innovative applications well beyond the realm of displays. Today this full breadth of the liquid crystalline state of matter is becoming increasingly recognized and numerous new and exciting lines of research are being opened up. We review this exciting development, focusing primarily on the physics aspects of the new research thrusts, in which liquid crystals - thermotropic as well as lyotropic - often meet other types of soft matter, such as polymers and colloidal nano- or microparticle dispersions. Because the field is of large interest also for researchers without a liquid crystal background we begin with a concise introduction to the liquid crystalline state of matter and the key concepts of the research field. We then discuss a selection of promising new directions, starting with liquid crystals for organic electronics, followed by nanotemplating and nanoparticle organization using liquid crystals, liquid crystal colloids (where the liquid crystal can constitute either the continuous phase or the disperse phase, as droplets or shells) and their potential in e.g. photonics and metamaterials, liquid crystal-functionalized polymer fibers, liquid crystal elastomer actuators, ending with a brief overview of activities focusing on liquid crystals in biology, food science and pharmacology.
Jan Lagerwall,Giusy Scalia 한국물리학회 2012 Current Applied Physics Vol.12 No.6
Liquid crystals constitute a fascinating class of soft condensed matter characterized by the counterintuitive combination of fluidity and long-range order. Today they are best known for their exceptionally successful application in flat panel displays, but they actually exhibit a plethora of unique and attractive properties that offer tremendous potential for fundamental science as well as innovative applications well beyond the realm of displays. Today this full breadth of the liquid crystalline state of matter is becoming increasingly recognized and numerous new and exciting lines of research are being opened up. We review this exciting development, focusing primarily on the physics aspects of the new research thrusts, in which liquid crystals e thermotropic as well as lyotropic e often meet other types of soft matter, such as polymers and colloidal nano- or microparticle dispersions. Because the field is of large interest also for researchers without a liquid crystal background we begin with a concise introduction to the liquid crystalline state of matter and the key concepts of the research field. We then discuss a selection of promising new directions, starting with liquid crystals for organic electronics, followed by nanotemplating and nanoparticle organization using liquid crystals, liquid crystal colloids (where the liquid crystal can constitute either the continuous phase or the disperse phase, as droplets or shells) and their potential in e.g. photonics and metamaterials, liquid crystal-functionalized polymer fibers, liquid crystal elastomer actuators, ending with a brief overview of activities focusing on liquid crystals in biology, food science and pharmacology.
Influence of Wetting on Morphology and Core Content in Electrospun Core–Sheath Fibers
Kim, Dae Kyom,Lagerwall, Jan P. F. American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.18
<P>Coaxial electrospinning allows easy and cost-effective realization of composite fibers at the nano- and microscales. Different multifunctional materials can be incorporated with distinct localization to specific regimes of the fiber cross section and extended internal interfaces. However, the final composite properties are affected by variations in internal structure, morphology, and material separation, and thus, nanoscale control is mandatory for high-performance application in devices. Here, we present an analysis with unprecedented detail of the cross section of liquid core-functionalized fibers, yielding information that is difficult to reveal. This is based on focused ion beam (FIB) lift-out and allowing HR-TEM imaging of the fibers together with nanoscale resolution chemical analysis using energy dispersive X-ray spectroscopy (EDS). Unexpectedly, core material escapes during spinning and ends up coating the fiber exterior and target substrate. For high core injection rate, a dramatic difference in fiber morphology is found, depending on whether the surface on which the fibers are deposited is hydrophobic or hydrophilic. The latter enhances postspinning extraction of core fluid, resulting in the loss of the functional material and collapsed fiber morphology. Finally, in situ produced TiO<SUB>2</SUB> nanoparticles dispersed in the polymer appear strikingly different when the core fluid is present compared to when the polymer solution is spun on its own.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-18/am504961k/production/images/medium/am-2014-04961k_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am504961k'>ACS Electronic Supporting Info</A></P>
Multifunctional responsive fibers produced by dual liquid crystal core electrospinning
Kye, YooMee,Kim, Changsoon,Lagerwall, Jan The Royal Society of Chemistry 2015 Journal of materials chemistry. C, Materials for o Vol.3 No.34
<P>We demonstrate that coaxial electrospinning with more than one core channel, each containing a different type of liquid crystal, can be used to produce multifunctional fibers in a one-step process. They respond to more than one stimulus or with multiple threshold values, and the individual cores may feature different physical properties such as iridescent reflection in one core and birefringence in another. In order to ensure good fiber morphology and intact, unmixed and well separated cores, two important precautions must be taken. First, the fibers should not be collected on a hydrophilic substrate, as this will lead to severe fiber deformation and core mixing after collection, as a result of capillary forces from the water that condenses on the fiber during spinning. Second, the addition of surfactants to the polymer solution should be avoided, although it may appear beneficial for the spinning process as it reduces surface tension and increases conductivity. This is because the surfactant enters the liquid crystal core, possibly together with water in the form of inverse micelles, seriously degrading the performance of the liquid crystal.</P>