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Author: Keul, Helmut × DDC: 540 × Type: article × Subject: Surfmer × WGL Institute: DWI ×

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    Synthesis of Polystyrene⁻Polyphenylsiloxane Janus Particles through Colloidal Assembly with Unexpected High Selectivity: Mechanistic Insights and Their Application in the Design of Polystyrene Particles with Multiple Polyphenylsiloxane Patches
    (Basel : MDPI, 2017) Mann, Daniel; Voogt, Stefanie; Keul, Helmut; Möller, Martin; Verheijen, Marcel; Buskens, Pascal
    Janus particles are of great research interest because of their reduced symmetry, which provides them with unique physical and chemical properties. Such particles can be prepared from spherical structures through colloidal assembly. Whilst colloidal assembly has the potential to be a low cost and scalable process, it typically lacks selectivity. As a consequence, it results in a complex mixture of particles of different architectures, which is tedious to purify. Very recently, we reported the colloidal synthesis of Au semishells, making use of polystyrene–polyphenylsiloxane Janus particles as an intermediate product (Chem. Commun. 2017, 53, 3898–3901). Here, we demonstrate that these Janus particles are realized through colloidal assembly of spherical glucose-functionalized polystyrene particles and an emulsion of phenyltrimethoxysilane in aqueous ammonia, followed by interfacial polycondensation to form the polyphenylsiloxane patch. Both the polystyrene spheres and the emulsion of Ph-TMS in aqueous ammonia are stabilized by a surfmer—a reactive surfactant. The colloidal assembly reported in this manuscript proceeds with an unexpected high selectivity, which makes this process exceptionally interesting for the synthesis of Janus particles. Furthermore, we report insights into the details of the mechanism of formation of these Janus particles, and apply those to adapt the synthesis conditions to produce polystyrene particles selectively decorated with multiple polyphenylsiloxane patches, e.g., raspberry particles.
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    Oligoglycidol-functionalised styrene macromolecules as reactive surfactants in the emulsion polymerisation of styrene: The impact of chain length and concentration on particle size and colloidal stability
    (Basel : MDPI AG, 2020) Waulthers, Kim; van Zandvoort, Ryan; Castermans, Sam; Welzen, Jeroen; Baeten, Evelien; Stout, Kathleen; Keul, Helmut; Mann, Daniel; Buskens, Pascal
    Reactive surfactants (surfmers), which are covalently attached to the surface of sub-micron sized polymer particles during emulsion polymerisation, are applied to tailor the surface functionality of polymer particles for an application of choice. We present a systematic study on the use of oligoglycidol-functionalised styrene macromolecules as surfmers in the emulsion polymerization of styrene. Firstly, we report the impact of the surfmer concentration on the particle size for polymerisations performed above and below the critical micelle concentration. Secondly, we report the influence of the oligoglycidol chain length on the particle size. Thirdly, we conducted experiments to analyse the influence of the surfmer concentration and its chain length on the colloidal stability of the aqueous polystyrene nanoparticles in sodium chloride solutions. We demonstrated that the size of polystyrene particles could be influenced by changing both the surfmer concentration and its chain length. Furthermore, we showed that the colloidal stability of the oligoglycidol-functionalized polystyrene particles is dependent on the particle size, and not directly related to the oligoglycidol chain length. © 2020 by the authors.