19 research outputs found

    Microgel degradation.

    No full text
    <p>AFM height retraces of cross-linker-free microgels pOEGMA<sub>80/0</sub> before (a) and after (b) incubation in 3 M HCl at 50°C for 7 weeks. Each image has a scan size of 5 μm x 5 μm. Particle heights and spreading diameters of partially hydrolyzed microgels deposited on glass substrates are plotted as function of incubation time (c).</p

    Viscosity data.

    No full text
    <p>Concentration dependence of the relative viscosities <i>η</i><sub>rel</sub> of cross-linker-free (pOEGMA<sub>80/0</sub>) and 5 mol-% PEG-DA (OEGMA<sub>80/5</sub>) containing microgels prepared at 80°C. The solid and dashed lines represent fits according to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0181369#pone.0181369.e001" target="_blank">Eq 1</a>.</p

    DLS and viscometry data.

    No full text
    <p>Summary of results from DLS and viscometry studies for cross-linker-free and microgels cross-linked with varying amounts of PEG-DA. The symbol <i>R</i><sub><i>H</i></sub> and <i>k</i> represent the hydrodynamic radius of the particles and the shift factor in the Batchelor equation (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0181369#pone.0181369.e001" target="_blank">Eq 1</a>), respectively.</p

    Oligo(ethylene glycol)-sidechain microgels prepared in absence of cross-linking agent: Polymerization, characterization and variation of particle deformability

    Get PDF
    <div><p>We present a systematic study of self-cross-linked microgels formed by precipitation polymerization of oligo ethylene glycol methacrylates. The cross-linking density of these microgels and, thus, the network flexibility can be easily tuned through the modulation of the reaction temperature during polymerization. Microgels prepared in absence of any difunctional monomer, i.e. cross-linker, show enhanced deformability and particle spreading on solid surfaces as compared to microgels cross-linked with varying amounts of poly(ethylene glycol diacrylate) (PEG-DA) in addition to self-crosslinking. Particles prepared at low reaction temperatures exhibit the highest degree of spreading due to the lightly cross-linked and flexible polymer network. Moreover, AFM force spectroscopy studies suggest that cross-linker-free microgels constitute of a more homogeneous polymer network than PEG-DA cross-linked particles and have elastic moduli at the particle apex that are ~5 times smaller than the moduli of 5 mol-% PEG-DA cross-linked microgels. Resistive pulse sensing experiments demonstrate that microgels prepared at 75 and 80°C without PEG-DA are able to deform significantly to pass through nanopores that are smaller than the microgel size. Additionally, we found that polymer network flexibility of microgels is a useful tool to control the formation of particle dewetting patterns. This offers a promising new avenue for build-up of 2D self-assembled particle structures with patterned chemical and mechanical properties.</p></div

    Formation of patterned particle assemblies.

    No full text
    <p>AFM height retraces in air of 10 mol-% cross-linked microgels deposited on APTMS-functionalized glass from a solution of 0.25 mg/mL pOEGMA<sub>80/10</sub> in 25 mM HEPES/150 mM NaCl (a, b), 10 mM HEPES (c), and DMSO (d). Images in panels (a), (c), and (d) have a scan size of 50 μm x 50 μm and the image in panel (b) has a scan size of 10 μm x 10 μm.</p

    Microgel deposition and particle height analysis.

    No full text
    <p>AFM height retraces of deposited microgels after drying. Microgels were synthesized at 80°C and contain different amounts of PEG-DA. From left to right: 0, 1, 5, and 10 mol-% PEG-DA. Each image has a scan size of 10 μm x 10 μm. (a). AFM height retraces of cross-linker-free microgels prepared at different polymerization temperatures. From left to right: 75, 80, 85, and 90°C. Each image has a scan size of 5 μm x 5 μm (b). The corresponding height profiles of the particles show the influence of cross-linking density on particle spreading (c). Panel (d) shows the particles heights after normalization to the corresponding hydrodynamic radii <i>R</i><sub>H</sub>. Errors were calculated <i>via</i> error propagation from the standard deviations derived for the AFM particle height and <i>R</i><sub>H</sub>.</p

    Nanopore translocation of microgels.

    No full text
    <p>Schematic description of the RPS technique using resizable elastomeric nanopores (a). Overlay of the current pulse signals generated by cross-linker-free particles and microgels cross-linked by 1, 5, and 10 mol-% PEG-DA (b). The inset shows the recording of multiple pulse signals generated by 5 mol-% cross-linked particles. Ratio between the particle sizes determined by RPS and DLS (c).</p

    Patterned particle monolayer prepared from soft and stiff microgel particles.

    No full text
    <p>AFM height retrace of a patterned microgel monolayer formed upon sequential deposition of stiff microgels pOEGMA<sub>80/10</sub> and soft microgels pOEGMA<sub>75/0</sub> on an APTMS-functionalized glass substrate. Scan size: 50 μm x 50 μm (a). AFM phase retrace of the patterned microgel monolayer recorded at a scan size of 10 μm x 10 μm (b).</p

    AFM force mapping.

    No full text
    <p>AFM topography maps of cross-linker-free microgel particles pOEGMA<sub>80/0</sub> (a) and 5 mol-% PEG-DA cross-linked particles pOEGMA<sub>80/5</sub> (b) after rehydration in 25 mM HEPES/150mM NaCl, pH 7.4. Each image has a scan size of 2 μm x 2 μm. For every square a complete force-distance curve was collected. The grids placed on top of the particles indicate the squares used for analysis. Particle heights and the corresponding Young´s moduli are plotted versus the particle cross section of microgels pOEGMA<sub>80/0</sub> (c) and pOEGMA<sub>80/5</sub> (d).</p

    Chain transfer reactions.

    No full text
    <p>Schematic representation of cross-linking <i>via</i> chain transfer reactions originating from the oligo ethylene glycols sidechains in pOEGMA microgels. Hydrogen atoms labeled in red can be abstracted by the attack of a radical that leads to the formation of midchain radicals. These radicals can attack other monomers or growing polymer chains, which results in branching and cross-linking.</p