title: Role of surfactant in the stability of liquid crystal-based nanocolloids.
abstract: We examine the dependence of liquid crystalline nanocolloid formation and stability on surfactant. Nanocolloids composed of polymerizable liquid crystal mesogens and cross-linking agents and capped with either ionic or nonionic surfactants are prepared via the miniemulsion technique. Colloids synthesized with anionic surfactant were stable and displayed 2D hexagonal packing when deposited via slow vertical pulling of the silicon substrate from an aqueous suspension. Liquid crystal nanocolloids stabilized with the nonionic, polar polymer polyvinyl alcohol (PVA) were stable in aqueous environments but coalesced upon drying to form relatively large, well-defined crystal-like structures with uniform birefringence. SEM images reveal that the coalesced structures have mesalike features. Polarized light, atomic force, and polarized Raman microscopy of these structures indicate that the liquid crystal molecules are arranged with their long molecular axis slightly tilted with respect to the surface normal. A mechanism is proposed to explain the formation of the mesalike structures from the nanocolloids. These studies provide fundamental insight into the incorporation and stabilization of polymerizable liquid crystal molecules into nanovolumes and open up opportunities for the incorporation of functionality and anisotropy into isotropically shaped nanocolloids.
authors.affiliation: Center for Bio/Molecular Science and Engineering, Chemistry Division, Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, USA.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Spillmann
authors.forename: Jawad
authors.initials: J
authors.lastname: Naciri
authors.forename: Kathryn J
authors.initials: KJ
authors.lastname: Wahl
authors.forename: Yancey H
authors.initials: YH
authors.lastname: Garner
authors.forename: Mu-San
authors.initials: MS
authors.lastname: Chen
authors.forename: Banahalli R
authors.initials: BR
authors.lastname: Ratna
mesh_terms: D003102:Colloids / Q000737:chemistry; D050866:Liquid Crystals / Q000737:chemistry* / Q000648:ultrastructure*; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D015394:Molecular Structure; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D044367:Phase Transition; D013059:Spectrum Analysis, Raman; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D003102:Colloids; D013501:Surface-Active Agents