title: Charged microcapsules for controlled release of hydrophobic actives. Part III: the effect of polyelectrolyte brush- and multilayers on sustained release.
abstract: Poly(methyl methacrylate) microspheres have been prepared by the internal phase separation method using either of the three conventional dispersants poly(vinyl alcohol) (PVA), poly(methacrylic acid) (PMAA), or the amphiphilic block copolymer poly(methyl methacrylate)-block-poly(sodium methacrylate). The block copolymer based microsphere, which has a polyelectrolyte brush on the surface, was surface modified with up to two poly(diallyldimethylammonium chloride)-poly(sodium methacrylate) bilayers. The microspheres were loaded with the hydrophobic dye 2-(4-(2-chloro-4-nitrophenylazo)-N-ethylphenylamino)ethanol (Disperse Red 13) and its release from aqueous dispersions of microspheres with the different surface compositions was measured by spectrophotometry. The burst fraction, burst rate and the diffusion constant were determined from a model combining burst and diffusive release. Out of the three dispersants, the block copolymer gave the slowest release of the dye, with respect to both burst release and diffusive release. A very pronounced further reduction of the diffusion constant was obtained by applying polyelectrolyte multilayers on top of the microspheres. However, the diffusion constant was very weakly dependent on further polyelectrolyte adsorption and one polyelectrolyte bilayer appeared to suffice.
authors.affiliation: Department of Chemical and Biological Engineering, Applied Surface Chemistry, Chalmers University of Technology, Göteborg, Sweden. markus.andersson@chalmers.se
authors.forename: Markus Andersson
authors.initials: MA
authors.lastname: Trojer
authors.forename: Helena
authors.initials: H
authors.lastname: Andersson
authors.forename: Ye
authors.initials: Y
authors.lastname: Li
authors.forename: Jonatan
authors.initials: J
authors.lastname: Borg
authors.forename: Krister
authors.initials: K
authors.lastname: Holmberg
authors.forename: Magnus
authors.initials: M
authors.lastname: Nydén
authors.forename: Lars
authors.initials: L
authors.lastname: Nordstierna
mesh_terms: D004573:Electrolytes / Q000138:chemical synthesis / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D008863:Microspheres; D015394:Molecular Structure; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D004573:Electrolytes; D011108:Polymers; D014867:Water