Stefan A F Bon

Publications of Stefan A F Bon

• High internal phase emulsion gels (HIPE-gels) from polymer dispersions reinforced with quadruple hydrogen bond functionality.

  Authors: Yunhua Chen, Nicholas Ballard, Florence Gayet, Stefan A F Bon

  Chemical communications (Cambridge, England). 12/2011; 48(8):1117-9.

  A convenient route to organogels templated by high internal phase emulsions has been developed. Key is the use of a waterborne polymer latex loaded with a multiple hydrogen bond (MHB) functionalityA convenient route to organogels templated by high internal phase emulsions has been developed. Key is the use of a waterborne polymer latex loaded with a multiple hydrogen bond (MHB) functionality that becomes disentangled and transfers across the oil-water interface forming a gel network in the oil phase via hydrogen bond interactions.

• Polymer vesicles with a colloidal armor of nanoparticles.

  Authors: Rong Chen, Daniel J G Pearce, Sara Fortuna, David L Cheung, Stefan A F Bon

  Journal of the American Chemical Society. 02/2011; 133(7):2151-3.

  The fabrication of polymer vesicles with a colloidal armor made from a variety of nanoparticles is demonstrated. In addition, it is shown that the armored supracolloidal structure can be postmodifiedThe fabrication of polymer vesicles with a colloidal armor made from a variety of nanoparticles is demonstrated. In addition, it is shown that the armored supracolloidal structure can be postmodified through film-formation of soft polymer latex particles on the surface of the polymersome, hereby effectively wrapping the polymersome in a plastic bag, as well as through formation of a hydrogel by disintegrating an assembled polymer latex made from poly(ethyl acrylate-co-methacrylic acid) upon increasing the pH. Furthermore, ordering and packing patterns are briefly addressed with the aid of Monte Carlo simulations, including patterns observed when polymersomes are exposed to a binary mixture of colloids of different size.

• Self-assembly of amphiphilic peanut-shaped nanoparticles.

  Authors: Stephen Whitelam, Stefan A F Bon

  The Journal of chemical physics. 02/2010; 132(7):074901.

  We use computer simulation to investigate the self-assembly of Janus-like amphiphilic peanut-shaped nanoparticles, finding phases of clusters, bilayers, and micelles in accord with ideas of packingWe use computer simulation to investigate the self-assembly of Janus-like amphiphilic peanut-shaped nanoparticles, finding phases of clusters, bilayers, and micelles in accord with ideas of packing familiar from the study of molecular surfactants. However, packing arguments do not explain the hierarchical self-assembly dynamics that we observe, nor the coexistence of bilayers and faceted polyhedra. This coexistence suggests that experimental realizations of our model can achieve multipotent assembly of either of two competing ordered structures.

• Unraveling mechanistic events in solids-stabilized emulsion polymerization by monitoring the concentration of nanoparticles in the water phase.

  Authors: Catheline A L Colard, Roberto F A Teixeira, Stefan A F Bon

  Langmuir : the ACS journal of surfaces and colloids. 02/2010; 26(11):7915-21.

  The fate of nanoparticles used as stabilizers in solids-stabilized, or Pickering, emulsion polymerization for the formation of armored hybrid polymer latexes was studied. We showed that diskThe fate of nanoparticles used as stabilizers in solids-stabilized, or Pickering, emulsion polymerization for the formation of armored hybrid polymer latexes was studied. We showed that disk centrifugation can be used as a powerful quantitative tool to analyze and determine the concentration of nanoparticles in the water phase throughout solids-stabilized emulsion polymerizations. We performed a series of emulsion polymerizations using vinyl acetate, vinyl pivalate, methyl methacrylate, or butyl acrylate in presence of silica nanoparticles (Ludox TM-40, ca. 25 nm in diameter). The developed method to quantify the number of silica nanoparticles in the water phase proved to be an invaluable tool for determining key features of the polymerization process. The obtained concentration profiles versus monomer conversion explained the existence of limited coalescence of armored particles in the later stages of the solids-stabilized emulsion polymerization process of vinyl acetate, leading to nonspherical structures. Moreover, we demonstrated that the correlation of the measured number of silica nanoparticles present in the water phase with the average particle sizes of the latex particles provided excellent predictions for the coverage of the armored layer of nanoparticles on the surfaces of the polymer particles, corresponding to observed packing patterns.

• Packing Patterns of Silica Nanoparticles on Surfaces of Armored Polystyrene Latex Particles.

  Authors: Sara Fortuna, Catheline A L Colard, Alessandro Troisi, Stefan A F Bon

  Langmuir : the ACS journal of surfaces and colloids. 06/2009;

  Fascinating packing patterns of identical spherical and discotic objects on curved surfaces occur readily in nature and science. Examples include C(60) fullerenes, (1, 2) 13-atom cuboctahedral metalFascinating packing patterns of identical spherical and discotic objects on curved surfaces occur readily in nature and science. Examples include C(60) fullerenes, (1, 2) 13-atom cuboctahedral metal clusters, (3) and S-layer proteins on outer cell membranes. (4) Numerous situations with surface-arranged objects of variable size also exist, such as the lenses on insect eyes, biomineralized shells on coccolithophorids, (5) and solid-stabilized emulsion droplets (6) and bubbles. (7) The influence of size variations on these packing patterns, however, is studied sparsely. Here we investigate the packing of nanosized silica particles on the surface of polystyrene latex particles fabricated by Pickering miniemulsion polymerization of submicrometer-sized armored monomer droplets. We are able to rationalize the experimental morphology and the nearest-neighbor distribution with the help of Monte Carlo simulations. We show that broadening of the nanoparticle size distribution has pronounced effects on the self-assembled equilibrium packing structures, with original 12-point dislocations or grain-boundary scars gradually fading out.

• Interaction of nanoparticles with ideal liquid-liquid interfaces.

  Authors: David L Cheung, Stefan A F Bon

  Physical review letters. 03/2009; 102(6):066103.

  Using molecular simulations the interaction between a noncharged nanoparticle and an ideal liquid-liquid interface is studied. The free energy profile as function of nanoparticle-interface separationUsing molecular simulations the interaction between a noncharged nanoparticle and an ideal liquid-liquid interface is studied. The free energy profile as function of nanoparticle-interface separation is determined using Wang-Landau sampling. Comparison between the simulation results and macroscopic theories shows that the latter give a poor description of the free energy profile. In particular, they underestimate both the range of interaction between the particle and the interface and its strength, with the discrepancy lessening as the particle radius increases. On increasing the solvent chemical potential the interaction strength increases and the interaction range decreases due to the increase in interfacial tension and consequent decrease in interfacial width.

• An "inside-out" microfluidic approach to monodisperse emulsions stabilized by solid particles.

  Authors: Zhihong Nie, Jai Il Park, Wei Li, Stefan A F Bon, Eugenia Kumacheva

  Journal of the American Chemical Society. 01/2009; 130(49):16508-9.

• Multilayered Nanocomposite Polymer Colloids Using Emulsion Polymerization Stabilized by Solid Particles.

  Authors: Patrick J Colver, Catheline A L Colard, Stefan A F Bon

  Journal of the American Chemical Society. 12/2008;

  We report a versatile emulsion polymerization process in which solid nanoparticles are used as stabilizer, thereby replacing the role of surfactants, allowing for simple fabrication of armoredWe report a versatile emulsion polymerization process in which solid nanoparticles are used as stabilizer, thereby replacing the role of surfactants, allowing for simple fabrication of armored nanocomposite polymer latexes. Use of a second conventional seeded emulsion polymerization step provides a straightforward route to more complex multilayered nanocomposite polymer colloids.

• Pickering stabilization as a tool in the fabrication of complex nanopatterned silica microcapsules.

  Authors: Stefan A F Bon, Tao Chen

  Langmuir : the ACS journal of surfaces and colloids. 10/2007; 23(19):9527-30.

  Complex silica-based microcapsules with nanopatterned features were made using Pickering stabilization as a fabrication tool. A sequential two-step liquid-liquid interface-driven assembly process wasComplex silica-based microcapsules with nanopatterned features were made using Pickering stabilization as a fabrication tool. A sequential two-step liquid-liquid interface-driven assembly process was employed using Laponite clay discs and Laponite armored polystyrene latex particles as solids to stabilize emulsion droplets on two different length scales. The discotic Laponite particles and poly(diethoxysiloxane) were used as silica sources. The ethoxy groups of the poly(diethoxysiloxane) were removed via a triethylamine-catalyzed interfacial hydrolysis and sol-gel reaction. The organic components were removed via a calcination step. The two-stage templating route provided siliceous microcapsules of which the capsule walls were decorated on either the outside or inside with nanocapsules composed of Laponite clay.

• Pickering miniemulsion polymerization using Laponite clay as a stabilizer.

  Authors: Stefan A F Bon, Patrick J Colver

  Langmuir : the ACS journal of surfaces and colloids. 08/2007; 23(16):8316-22.

  Solid-stabilized, or Pickering, miniemulsion polymerizations using Laponite clay discs as stabilizer are investigated. Free radical polymerizations are carried out using a variety of hydrophobicSolid-stabilized, or Pickering, miniemulsion polymerizations using Laponite clay discs as stabilizer are investigated. Free radical polymerizations are carried out using a variety of hydrophobic monomers (i.e., styrene, lauryl (meth)acrylate, butyl (meth)acrylate, octyl acrylate, and 2-ethyl hexyl acrylate). Armored latexes, of which the surfaces of the particles are covered with clay discs, are obtained, as confirmed by scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). Overall polymerization kinetics of the Pickering miniemulsion polymerizations of styrene were investigated via gravimetry. Comparison with the bulk polymerization analogue clearly shows compartmentalization. Moreover, retardation effects up to intermediate monomer conversions are observed; they are more prominent for the smaller particles and are ascribed to the Laponite clay. A model is presented that allows for the prediction of the average particle size of the latexes produced as a function of the amounts of monomer and Pickering stabilizers used. It shows that under specific generic conditions the number of clay discs used correlates in a linear fashion with the total surface area of the latex particles. This is a direct result of the reversibility of the Laponite clay disc adhesion process under the emulsification conditions (i.e., sonication) used.

• Route to stable non-spherical emulsion droplets

  Authors: Stefan A.F. Bon, Steven D. Mookhoek, Patrick J. Colver, Hartmut R. Fischer, Sybrand van der Zwaag

  European Polymer Journal.

  A route to the production of stable non-spherical emulsion droplets has been developed by pushing millimeter-sized liquid droplets stabilized by an excess amount of solid Pickering particles throughA route to the production of stable non-spherical emulsion droplets has been developed by pushing millimeter-sized liquid droplets stabilized by an excess amount of solid Pickering particles through a narrow capillary. This excess amount allows for the full coverage of the newly created droplets’ interface during deformation. Upon exiting the capillary the adhered particles wedge, or “jam”, on the surface preserving the non-spherical shape. Stable millimeter-sized non-spherical liquid droplets with aspect ratios exceeding 10 and cross-sections in line with capillary dimensions are easily obtained. Post-modification can be performed in conventional reactors. The ability to fabricate non-spherical droplets creates exciting opportunities in areas such as self-healing polymer composites.