Research Article Rheology and Shear-Induced Textures of Silver Nanowire Lyotropic Liquid Crystals Teng Xu and Virginia A. Davis Department of Chemical Engineering, Auburn University, Auburn, AL 36849, USA Correspondence should be addressed to Virginia A. Davis; davisva@auburn.edu Received 6 September 2015; Accepted 26 November 2015 Academic Editor: Luca Valentini Copyright © 2015 T. Xu and V. A. Davis. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We report the rheological and microstructural shear response of a mixture of polyvinylpyrrolidone (PVP) coated silver nanowires and nanoparticle aggregates (Ag) dispersed in ethylene glycol (EG) or water (H 2 O). Biphasic and liquid crystalline dispersions exhibited rheological characteristics similar to those of lyotropic liquid crystalline polymers (LCPs). Te viscosity versus concentration curve for Ag-EG dispersions showed a viscosity minimum at a silver concentration between 2.2 vol.% and 2.9 vol.%; this is indicative of the transition to an entirely liquid crystalline phase. Te rheology results were consistent with optical microscopy observations that at 2.9 vol.% the sample was entirely birefringent; this is another indication of liquid crystalline phase formation. Shear had a signifcant efect on the microstructure of the dispersions and dried coatings. Depending on the shear rate, worm or shear banding Structures were observed. 1. Introduction Inorganic nanocylinders (i.e., nanorods, nanowires, and nanotubes) are promising materials due to their excellent plasmonic, optoelectronic, and catalytic properties [1–3]. Tere have been ongoing improvements in the reproducibil- ity and scalability of nanocylinder synthesis, but scalable methods for controlled assembly over large areas remain a persistent challenge. Fluid phase processing methods are a promising route; both the scalability and infrastructure for producing coatings from complex fuid dispersions are well established [4–8]. In addition, many nanocylinders are synthesized in a liquid dispersion. Experimental results have shown that nanocylinder coatings and flms with controlled, uniform orientation have signifcantly improved optical [9, 10] and electrical [11–13] properties, and they can be used as building blocks for functional devices. However, controlling orientation in nanocylinder coatings requires understanding dispersions’ rheological and microstructural response to shear. Silver nanowires’ excellent optical, electrical, thermal, and antimicrobial properties have caused them to be explored for transparent conductive displays, solar cell components, surface-enhanced Raman scattering (SERS) substrates, elec- trochemical capacitors, and antimicrobial surfaces [14–17]. In our previous work, we reported demixed nematic liq- uid crystalline phase formation in a system comprised of polyvinylpyrrolidone (PVP) coated silver nanowires and nanoparticle aggregates dispersed in ethylene glycol/water (EG/H 2 O) [18]. In this work, we report the results of more detailed studies on the rheological and microstructural response of these dispersions to shear. Te rheological prop- erties are analogous to those reported for classical rod-like liquid crystalline polymers (LCPs) [19–22]. We also report that shearing the dispersions results in complex microstruc- tures. For example, applying a shear rate of approximately 200 s −1 results in a worm-like texture in biphasic dispersions; this texture is stable for several hours due to the long relaxation time of the high aspect ratio Ag nanocylinders. At higher shear rates, the silver nanowires align at the top of the coating while the spherical aggregates pack at the bottom of the coating and shear banding can occur. Tis intriguing range of microstructures is promising for the controlled assembly of not only silver dispersions, but also multicom- ponent dispersions of nanocylinders and nanoparticles. Hindawi Publishing Corporation Journal of Nanomaterials Volume 2015, Article ID 939587, 9 pages http://dx.doi.org/10.1155/2015/939587