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    Charged microcapsules for controlled release of hydrophobic actives. Part I: encapsulation methodology and interfacial properties

    Year: 2013

    Journal: Soft Matter, 2013,9, 1468-1477, 20130630

    Authors: Markus Andersson Trojer a, Ye Li a, Christoffer Abrahamsson a, Azmi Mohamed b, Julian Eastoe b, Krister Holmberg a, Magnus Nydén a c

    Last authors: Magnus Nydén

    Organizations: a Department of Chemical and Biological Engineering, Applied Surface Chemistry, Chalmers University of Technology, Göteborg, Sweden E-mail: markus.andersson@chalmers.se b School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK c Ian Wark Research Institute, University of South Australia, Mawson Lakes Campus, Adelaide, Australia

    Country: Sverige, Sweden, UK, England, Australia

    Highly charged microcapsules have been prepared using the internal phase separation technique. The charges are introduced by using ionic dispersants, which have been characterized with respect to surface activity with a quartz crystal microbalance with dissipation monitoring and with optical tensiometry. The long-term stability of the microcapsule suspension without excess dispersant, as well as the stability at high ionic strength, have been investigated. Three types of ionic dispersants have been evaluated: a weak polyacid (poly(methacrylic acid)), a small set of ionic amphiphilic block copolymers of poly(methyl methacrylate)-block-poly(sodium (meth)acrylate) type and an oil-soluble anionic surfactant, sodium 1,5-dioxo-1,5-bis(3,5,5-trimethylhexyloxy)-3-((3,5,5-trimethylhexyloxy)carbonyl)pentane-2-sulfonate, in combination with a water-soluble polycation, poly(diallyldimethylammonium chloride). The block copolymer based microcapsule suspension is characterized by a long-term stability, even at high ionic strength, provided by electrostatic and steric stabilization. The weak polyacid based microcapsule suspension is stable for a few weeks, after which aggregation starts due to desorption of the dispersant. The surfactant–polycation based microcapsules appear to have a multicore morphology in contrast to the weak polyacid or block copolymer based microcapsules, which are core–shell particles.