title: Narrowly size-distributed cobalt salt containing poly(2-hydroxyethyl methacrylate) particles by inverse miniemulsion.
abstract: Cobalt-containing hybrid particles have been prepared through the encapsulation of cobalt tetrafluoroborate hexahydrate (CoTFB) via inverse miniemulsion polymerization of 2-hydroxyethyl methacrylate (HEMA). We systematically varied the amount and type of cosolvent (water, methanol, ethanol, ethylene glycol), apolar continuous phase (cyclohexane, isooctane, isopar M, hexadecane), amount of cobalt salt, and molecular weight of the polymeric surfactant. The influence of those parameters on the particle size, size distribution, and particle morphology were investigated. Narrowly size-distributed hybrid particles with good colloidal stability could be obtained in a wide range of cobalt content between 5.7 and 22.6 wt % salt relative to the monomer. The addition of a cosolvent such as water not only promotes the loading of metal salt but also has a positive influence on narrowing the particle size distribution. We assume that generally narrowly size-distributed particles can be obtained for a large variety of combinations of polar/apolar phase by adjusting the balance between osmotic and Laplace pressure via the solubility of the metal salt in the continuous phase and lowering the interfacial tension by adjusting the hydrophilic-lipophilic balance (HLB) value of the surfactant. The results show a significant advantage of the inverse miniemulsion over the direct system with respect to the variability and total amount of metal salt without losing the narrow particle size distribution and colloidal stability.
authors.affiliation: Institute of Organic Chemistry III-Macromolecular Chemistry and Organic Materials, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany.
authors.forename: Zhihai
authors.initials: Z
authors.lastname: Cao
authors.forename: Zhuo
authors.initials: Z
authors.lastname: Wang
authors.forename: Christine
authors.initials: C
authors.lastname: Herrmann
authors.forename: Ulrich
authors.initials: U
authors.lastname: Ziener
authors.forename: Katharina
authors.initials: K
authors.lastname: Landfester
mesh_terms: D003035:Cobalt / Q000737:chemistry*; D004655:Emulsions / Q000737:chemistry; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010316:Particle Size; D011102:Polyhydroxyethyl Methacrylate / Q000737:chemistry*; D012492:Salts / Q000737:chemistry; D013499:Surface Properties
chemical_list: D004655:Emulsions; D009942:Organometallic Compounds; D012492:Salts; D011102:Polyhydroxyethyl Methacrylate; D003035:Cobalt