title: Uniform discotic wax particles via electrospray emulsification.
abstract: We present a novel colloidal discotic system: the formation and self-assembling of wax microdisks with a narrow size distribution. Uniform wax emulsions are first fabricated by electrospraying of melt alpha-eicosene. The size of the emulsions can be flexibly tailored by varying the flow rate of the discontinuous phase, its electric conductivity, and the applied voltage. The process of entrainment of wax droplets, vital for obtaining uniform emulsions, is facilitated by the reduction of air-water surface tension and the density of the continuous phase. Then uniform wax discotic particles are produced via phase transition, during which the formation of a layered structure of the rotator phase of wax converts the droplets, one by one, into oblate particles. The time span for the conversion from spherical emulsions to disk particles is linearly dependent on the size of droplets in the emulsion, indicating the growth of a rotator phase from surface to the center is the limiting step in the shape transition. Using polarized light microscopy, the self-assembling of wax disks is observed by increasing disk concentration and inducing depletion attraction among disks, where several phases, such as isotropic, condensed, columnar stacking, and self-assembly of columnar rods are present sequentially during solvent evaporation of a suspension drop.
authors.affiliation: Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX 77843-3122, USA.
authors.forename: Andres F
authors.initials: AF
authors.lastname: Mejia
authors.forename: Peng
authors.initials: P
authors.lastname: He
authors.forename: Dawei
authors.initials: D
authors.lastname: Luo
authors.forename: Manuel
authors.initials: M
authors.lastname: Marquez
authors.forename: Zhengdong
authors.initials: Z
authors.lastname: Cheng
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D004553:Electric Conductivity; D004563:Electrochemistry / Q000295:instrumentation / Q000379:methods*; D004655:Emulsions / Q000737:chemistry*; D000431:Ethanol / Q000737:chemistry; D050866:Liquid Crystals / Q000737:chemistry; D010316:Particle Size; D044367:Phase Transition; D013500:Surface Tension; D014867:Water / Q000737:chemistry
chemical_list: D000475:Alkenes; D004655:Emulsions; D014867:Water; D000431:Ethanol; C542652:alpha-eicosene