Hans-Jürgen Butt

Max Planck Institute for Polymer Research, Mayence, Rheinland-Pfalz, Germany

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Publications (316)1566.57 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Poly(n-butylacrylate)@polystyrene nanoparticles behaving as a capsule-based sealing nanoadditive are synthesized through an optimized semicontinuous emulsion polymerization protocol. Solid state time-domain 1H-NMR and 13C magic angle spinning (MAS) NMR analysis suggest strong phase separation. Line width of 13C resonances in cross polarization and single pulse experiment MAS-NMR spectra indicates that the peculiar mobility of each phase is preserved at the nanoscale. Atomic force spectroscopy (AFM) shows the permanence of spherical shape in absence of solvent (i.e., subsequent to strong capillary and surface forces) up to moderate external load, as well as the possibility of plastically deforming the polystyrene shell and ultimately triggering the nanoparticle flow at higher force loads. The breakdown characteristic of the nanoparticle shows for the first time baroplastic behavior on a single particle with precise biphasic core@shell morphology.
    No preview · Article · Jan 2016 · Macromolecular Rapid Communications
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    Jing Xie · Mikheil Doroshenko · Ulrich Jonas · Hans-Jürgen Butt · Kaloian Koynov
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    ABSTRACT: We report a new strategy for the preparation of well-defined and mechanically stable porous nanostructures with tunable porosity. Silica inverse opals, which are known as a model system for a porous periodic nanostructure, were grafted with brushes of the thermoresponsive poly(N-isopropylacrylamide) grown via atom transfer radical polymerization. By tuning the temperature, the swelling state of the brush layer is reversibly altered, and with this we were able to control the overall porosity of the system and, thus, the mobility of small penetrants. Fluorescence correlation spectroscopy, a method combining single molecule sensitivity with small probing volume (<1 μm3), was used to directly monitor and quantify in situ the changes in the penetrants’ mobility.
    Full-text · Article · Jan 2016 · ACS Macro Letters
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    ABSTRACT: The use of self-assembled nanostructures consisting of red-light-responsive Ru(II)-containing block copolymers (BCPs) for anticancer phototherapy is demonstrated. Three Ru-containing BCPs with different molecular weights are synthesized. Each BCP contains a hydrophilic poly(ethylene glycol) block and an Ru-containing block. In the Ru-containing block, more than half of the side chains are coordinated with [Ru(2,2':6',2''-terpyridine)(2,2'-biquinoline)](2+) , resulting in more than 40 wt% Ru complex in the BCPs. The Ru complex acts as both a red-light-cleavable moiety and a photoactivated prodrug. Depending on their molecular weights, the BCPs assemble into micelles, vesicles, and large compound micelles. All of the BCP assemblies are taken up by cancer cells. Red-light irradiation releases the Ru complex and generates singlet oxygen ((1) O2 ) in cancer cells. The released Ru complex and (1) O2 inhibit the growth of cancer cells. Among the three BCP assemblies, the BCP micelle exhibits the most efficient cellular uptake and best anticancer performance.
    No preview · Article · Dec 2015 · Advanced Healthcare Materials
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    ABSTRACT: Using fluorescence correlation spectroscopy, we investigated the diffusion dynamics of a molecular probe in solutions of polystyrene and polybutadiene with different molar masses (Mw) and molecular architectures (stars, combs) over a broad concentration range (c). Whereas the tracer diffusion coefficient D was found to be insensitive to variations in Mw and architecture, the obtained master plot D(c) was polymer-specific, reflecting additional friction effects related to the concentration-dependent glass transition temperature Tg(c). This effect is fully suppressed for the same probe diffusion in poly(dimethylsiloxane) solutions with very low and virtually concentration-independent Tg. Hence, a universal master curve of D vs c can be obtained when Tg
    No preview · Article · Dec 2015 · Macromolecules
  • Doris Vollmer · Hans-Jürgen Butt

    No preview · Article · Nov 2015 · Nature
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    ABSTRACT: Dielectric (DS), IR spectroscopy and 1H MAS NMR are employed in studying ice/water confined in nanoporous alumina with pore diameters ranging from 400 nm down to 25 nm. Within nanoporous alumina there is a transformation from heterogeneous nucleation of hexagonal ice in the larger pores to homogeneous nucleation of cubic ice in the smaller pores. DS and IR show excellent agreement in the temperature interval and pore size dependence of the transformation. DS further revealed two dynamic processes under confinement. The "fast" and "slow" processes with an Arrhenius temperature dependence are attributed to ice and supercooled water relaxation, respectively. The main relaxation process of ice under confinement ("slow" process) has an activation energy of 44±2 kJ/mol. The latter is in agreement with the reported relaxation times and activation energy of cubic ice prepared following a completely different route (by pressure). 1H MAS NMR provided new insight in the state of ice structures as well as of supercooled water. Under confinement, a layer of liquid-like water coexisting with ice structures. In addition, both ice structures under confinement appear to be more ordered than bulk hexagonal ice. Supercooled water in the smaller pores is different from bulk water. It shows a shift of the signal towards higher chemical shift values which may suggest stronger hydrogen bonding between the water molecules or increasing interactions with the AAO walls.
    No preview · Article · Oct 2015 · The Journal of Physical Chemistry B
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    ABSTRACT: Perylene diimide (PDI)-based organic photovoltaic devices can potentially deliver high power conversion efficiency values provided the photon energy absorbed is utilized efficiently in charge transfer (CT) reactions instead of being consumed in non-radiative energy transfer (ET) steps. Hitherto, it remains unclear whether ET or CT primarily drives the photoluminescence (PL) quenching of the PDI excimer state in PDI-based blend films. Here, we affirm the key-role of the thermally-assisted PDI excimer diffusion and subsequent CT reaction in the process of PDI excimer PL deactivation. For our study we perform PL quenching experiments in the model PDI-based composite made of poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo [1,2-b;4,5-b']dithiophene-2,6-diyl-alt-(4-(2- ethylhexanoyl)-thieno[3,4-b]thiophene-)-2-6-diyl)] (PBDTTT-CT) polymeric donor mixed with the N,N'-bis(1-ethylpropyl)-perylene-3,4,9,10-tetracarboxylic diimide (PDI) acceptor. Despite the strong spectral overlap between the PDI excimer PL emission and UV-Vis absorption of PBDTTT-CT, two main observations indicate that no significant ET component operates in the overall PL quenching; the PL intensity of the PDI excimer (i) increases with decreasing temperature, and (ii) remains unaffected even in the presence of 10 wt% content of the PBDTTT-CT quencher. Temperature dependent wide-angle X-ray scattering experiments further indicate that non-radiative resonance ET is highly improbable due to the large size of PDI domains. The dominance of the CT over the ET process is verified by the high performance of devices with an optimum composition of 30:70 PBDTTT-CT:PDI. By adding 0.4 vol.% of 1,8-diiodooctane we verify the plasticization of the polymer side-chains that balance the charge transport properties of the PBDTTT-CT:PDI composite and result in additional improvement in the device efficiency. The temperature-dependent spectral width of the PDI excimer PL band suggests the presence of energetic disorder in the PDI excimer excited state manifold.
    No preview · Article · Oct 2015 · ACS Applied Materials & Interfaces
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    ABSTRACT: A method for mesoporous supraparticle synthesis on superamphiphobic surfaces is designed. Therefore, supraparticles assembled with nanoparticles are synthesized by the evaporation of nanoparticle dispersion drops on the superamphiphobic surface. For synthesis, no further purification is required and no organic solvents are wasted. Moreover, by changing the conditions such as drop size and concentration, supraparticles of different size, composition, and architecture are fabricated.
    No preview · Article · Oct 2015 · Advanced Materials
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    Jing Xie · Keita Nakai · Sayaka Ohno · Hans-Juergen Butt · Kaloian Koynov · Shin-ichi Yusa
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    ABSTRACT: Fluorescence correlation spectroscopy (FCS) was applied to directly monitor the hydrophobic collapse of pH-responsive hairy nanoparticles at the individual particle level. To this end, fluorescent nanoparticles (hydrodynamic radius 20 nm) with polystyrene core and poly(N,N-diethylaminoethyl methacrylate) (PDEA) shell were prepared and used as a model system. Dynamic light scattering and turbidity measurements showed that the hydrophobic collapse of the hairs at high pH values is associated with strong interparticle aggregation that hinders determination of individual particles size. However, at the ultralow concentrations assessable by FCS (less than one particle per femtoliter) the aggregation was prevented. Thus, the pH-induced change in the particles size caused by the swelling or the collapse of the PDEA hairs was systematically measured and compared with that of individual freely diffusing PDEA chains under similar conditions.
    Full-text · Article · Sep 2015 · Macromolecules
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    ABSTRACT: Pottery was a traditional art and technology form in pre-colonial Amazonian civilizations, widely used for cultural expression objects, utensils and as cooking vessels. Abundance and workability of clay made it an excellent choice. However, inferior mechanical properties constrained their functionality and durability. The inclusion of reinforcement particles is a possible route to improve its resistance to mechanical and thermal damage. The Amazonian civilizations incorporated freshwater tree sponge spicules (cauixí) into the clay presumably to prevent shrinkage and crack propagation during drying, firing and cooking. Here we show that isolated siliceous spicules are almost defect-free glass fibres with exceptional mechanical stability. After firing, the spicule Young's modulus increases (from 28 ± 5 GPa to 46 ± 8 GPa) inferring a toughness increment. Laboratory-fabricated ceramic models containing different inclusions (sand, glass-fibres, sponge spicules) show that mutually-oriented siliceous spicule inclusions prevent shrinkage and crack propagation leading to high stiffness clays (E = 836 ± 3 MPa). Pre-colonial amazonian potters were the first civilization known to employ biological materials to generate composite materials with enhanced fracture resistance and high stiffness in the history of mankind.
    Full-text · Article · Sep 2015 · Scientific Reports
  • Si Wu · Hans-Jürgen Butt
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    ABSTRACT: The near-infrared (NIR) region of the spectrum is called the "therapeutic window" because NIR light can penetrate deeply into tissue. Therefore, NIR-sensitive materials are attractive for biomedical applications. Recently, upconverting nanoparticles (UCNPs) were used to construct NIR-sensitive materials. UCNPs convert NIR light to UV or visible light, which can trigger photoreactions of photosensitive materials. Here, how to use UCNPs to construct NIR-sensitive materials is introduced, applications of NIR-sensitive materials with a focus on biomedical applications are highlighted, and the associated challenges are discussed.
    No preview · Article · Sep 2015 · Advanced Materials
  • Dongsheng Wang · Manfred Wagner · Hans-Jürgen Butt · Si Wu
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    ABSTRACT: We report a novel red-light-responsive supramolecule. The tetra-ortho-methoxy-substituted azobenzene (mAzo) and β-cyclodextrin (β-CD) spontaneously formed a supramolecular complex. The substituted methoxy groups shifted the responsive wavelength of the azo group to the red light region, which is in the therapeutic window and desirable for biomedical applications. Red light induced the isomerization of mAzo and the disassembly of the mAzo/β-CD supramolecular complex. We synthesized a mAzo-functionalized polymer and a β-CD-functionalized polymer. Mixing the two polymers in an aqueous solution generated a supramolecular hydrogel. Red light irradiation induced a gel-to-sol transition as a result of the disassembly of the mAzo/β-CD complexes. Proteins were loaded in the hydrogel. Red light could control protein release from the hydrogel in tissue due to its deep penetration depth in tissue. We envision the use of red-light-responsive supramolecules for deep-tissue biomedical applications.
    No preview · Article · Aug 2015 · Soft Matter
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    Xu Deng · Lena Mammen · Hans-Jürgen Butt · Doris Vollmer

    Full-text · Dataset · Aug 2015
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    ABSTRACT: For a liquid droplet to slide down a solid planar surface, the surface usually has to be tilted above a critical angle of approximately 10°. By contrast, droplets of nearly any liquid "slip" on lubricant-infused textured surfaces - so termed slippery surfaces - when tilted by only a few degrees. The mechanism of how the lubricant alters the static and dynamic properties of the drop remains elusive because the drop-lubricant interface is hidden. Here, we image the shape of drops on lubricant-infused surfaces by laser scanning confocal microscopy. The contact angle of the drop-lubricant interface with the substrate exceeds 140°, although macroscopic contour images suggest angles as low as 60°. Confocal microscopy of moving drops reveals fundamentally different processes at the front and rear. Drops recede via discrete depinning events from surface protrusions at a defined receding contact angle, whereas the advancing contact angle is 180°. Drops slide easily, as the apparent contact angles with the substrate are high and the drop-lubricant interfacial tension is typically lower than the drop-air interfacial tension. Slippery surfaces resemble superhydrophobic surfaces with two main differences: drops on a slippery surface are surrounded by a wetting ridge of adjustable height and the air underneath the drop in the case of a superhydrophobic surface is replaced by lubricant in the case of a slippery surface.
    Preview · Article · Aug 2015 · Soft Matter
  • Yasuhito Suzuki · Martin Steinhart · Hans-Jürgen Butt · George Floudas
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    ABSTRACT: The nucleation mechanism of water (heterogeneous/homogeneous) can be regulated by confinement within nanoporous alumina. The kinetics of ice nucleation is studied in confinement by employing dielectric permittivity as a probe. Both heterogeneous and homogeneous nucleation, obtained at low and high undercooling respectively, are stochastic in nature. The temperature interval of metastability extends over ~ 4 °C and 0.4 °C for heterogeneous and homogenous nucleation, respectively. Nucleation within a pore is spread to all pores in the template. We have examined a possible coupling of all pores through a heat wave and a sound wave, with the latter being a more realistic scenario. In addition, dielectric spectroscopy indicates that prior to crystallization undercooled water molecules relax with an activation energy of ~50 kJ/mol and this process acts as precursor to ice nucleation.
    No preview · Article · Aug 2015 · The Journal of Physical Chemistry B
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    ABSTRACT: Superhydrophobic surfaces are usually characterized by a high apparent contact angle of water drops in air. Here we analyze the inverse situation: Rather than focusing on water repellency in air we measure the attractive interaction of air bubbles and super¬hydro-phobic surfaces in water. Forces were measured between micro¬bubbles with radii R of 40-90 µm attached to an atomic force microscope cantilever and submerged superhydrophobic surfaces. In addition, forces between macros¬copic bubbles (R = 1.2 mm) at the end of capillaries and superhydrophobic surfaces were measured. As superhydrophobic surfaces we applied soot-tem¬plated surfaces, nanofilament surfaces, micropillar arrays with flat top faces and decorated micropillars. Depending on the specific structure of the superhydro¬phobic surfaces and the presence and amount of entrapped air different interactions were observed. Soot-templated surfaces in the Cassie state showed superaerophilic behavior: Once the electrostatic double-layer force and a hydrodynamic repulsion were over¬come, bubbles jumped onto the surface and fully merged with the entrapped air. On nano¬filaments and micropillar arrays we observed in addition the formation of sessile bubbles with finite contact angles below 90° or the attachment of bubbles, which retained their spherical shape.
    No preview · Article · Jun 2015 · Langmuir
  • Zhijun Chen · Wen Sun · Hans-Jürgen Butt · Si Wu
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    ABSTRACT: Upconverting nanoparticles (UCNPs) convert near-infrared (NIR) light into UV or visible light that can trigger photoreactions of photosensitive compounds. In this paper, we demonstrate how to reduce the intensity of NIR light for UCNP-assisted photochemistry. We synthesized two types of UCNPs with different emission bands and five photosensitive compounds with different absorption bands. A λ=974 nm laser was used to induce photoreactions in all of the investigated photosensitive compounds in the presence of the UCNPs. The excitation thresholds of the photoreactions induced by λ=974 nm light were measured. The lowest threshold was 0.5 W cm(-2) , which is lower than the maximum permissible exposure of skin (0.726 W cm(-2) ). We demonstrate that low-intensity NIR light can induce photoreactions after passing through a piece of tissue without damaging the tissue. Our results indicate that the threshold for UCNP- assisted photochemistry can be reduced by using highly photosensitive compounds that absorb upconverted visible light. Low excitation intensity in UCNP-assisted photochemistry is important for biomedical applications because it minimizes the overheating problems of NIR light and causes less photodamage to biomaterials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    No preview · Article · May 2015 · Chemistry - A European Journal
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    ABSTRACT: Many natural materials are complex composites whose mechanical properties are often outstanding considering the weak constituents from which they are assembled. Nacre, made of inorganic (CaCO3 ) and organic constituents, is a textbook example because of its strength and toughness, which are related to its hierarchical structure and its well-defined organic-inorganic interface. Emulating the construction principles of nacre using simple inorganic materials and polymers is essential for understanding how chemical composition and structure determine biomaterial functions. A hard multilayered nanocomposite is assembled based on alternating layers of TiO2 nanoparticles and a 3-hydroxy-tyramine (DOPA) substituted polymer (DOPA-polymer), strongly cemented together by chelation through infiltration of the polymer into the TiO2 mesocrystal. With a Young's modulus of 17.5 ± 2.5 GPa and a hardness of 1.1 ± 0.3 GPa the resulting material exhibits high resistance against elastic as well as plastic deformation. A key feature leading to the high strength is the strong adhesion of the DOPA-polymer to the TiO2 nanoparticles. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Full-text · Article · Apr 2015 · Macromolecular Rapid Communications
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    ABSTRACT: We studied experimentally and theoretically the direction-dependent elastic and electromagnetic wave propagation in a supported film of hybrid PMMA (poly[methyl-methacrylate])-TiO2 superlattice (SL). In the direction normal to the layers, this one-dimensional periodic structure opens propagation band gaps for both hypersonic (GHz) phonons and near-UV photons. The high mismatch of elastic and optical impedance results in a large dual phoxonic band gap. The presence of defects inherent to the spin-coating fabrication technique is sensitively manifested in the band gap region. Utilizing Brillouin light scattering, phonon propagation along the layers was observed to be distinctly different from propagation normal to them and can, under certain conditions (SL thickness and substrate elasticity), reveal the nanomechanical properties of the constituent layers. Besides the first realization of unidirectional phoxonic behavior, hybrid (soft-hard) periodic materials are a promising simple platform for opto-acoustic interactions and applications such as filters and Bragg mirrors.
    Full-text · Article · Apr 2015 · ACS Applied Materials & Interfaces
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    ABSTRACT: Unlabelled: The performance of organic photovoltaic devices (OPV) with nanostructured polymer:perylene diimide (PDI) photoactive layers approaches the levels of the corresponding polymer:fullerene systems. Nevertheless, a coherent understanding of the difficulty for PDI-based OPV devices to deliver high power conversion efficiencies remains elusive. Here we perform a comparative study of a set of four different polymer:PDI OPV model systems. The different device performances observed are attributed to differences in the nanostructural motif of these composites, as determined by wide-angle X-ray scattering (WAXS) measurements. Long-range structural order in the PDI domain dictates (i) the stabilization energy and (ii) the concentration of the PDI excimers in the composites. The quenching of the PDI excimer photoluminescence (PL) is found to be insensitive to the former, but it depends on the latter. High PL quenching occurs for the low concentration of PDI excimers that are formed in PDI columns with a length comparable to the PDI excimer diffusion length. The stabilization of the PDI excimer state increases as the long-range order in the PDI domains improves. The structural order of the PDI domains primarily affects charge transport. Electron mobility reduces as the size of the PDI domain increases, suggesting that well-ordered PDI domains suffer from poor electronic connectivity. WAXS further reveals the presence of additional intermolecular PDI interactions, other than the direct face-to-face intermolecular coupling, that introduce a substantial energetic disorder in the polymer:PDI composites. Conventional device architectures with hole-collecting ITO/PEDOT:PSS bottom electrodes are compared with inverted device architectures bearing bottom electron-collecting electrodes of ITO/ZnO. In all cases the ZnO-functionalized devices surpass the performance of the conventional device analogues. X-ray photoelectron spectroscopy explains that in Pedot: PSS-functionalized devices, the PDI component preferentially segregates closer to the hydrophilic Pedot: PSS electrode, thus impeding the efficient charge extraction and limiting device photocurrent.
    Full-text · Article · Mar 2015 · ACS Applied Materials & Interfaces

Publication Stats

9k Citations
1,566.57 Total Impact Points

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  • 2002-2015
    • Max Planck Institute for Polymer Research
      Mayence, Rheinland-Pfalz, Germany
  • 2012
    • University of Ioannina
      • Department of Physics
      Yannina, Epirus, Greece
  • 2010
    • University of Crete
      Retimo, Crete, Greece
  • 2009
    • Technical University Darmstadt
      • Center of Smart Interfaces (CSI)
      Darmstadt, Hesse, Germany
  • 2000-2007
    • Universität Siegen
      • Department of Chemistry and Biology
      Siegen, North Rhine-Westphalia, Germany
  • 2001
    • Philipps University of Marburg
      Marburg, Hesse, Germany
  • 1998-2000
    • Johannes Gutenberg-Universität Mainz
      • Institute of Physical Chemistry
      Mainz, Rhineland-Palatinate, Germany
  • 1994-1997
    • Max Planck Institute of Biophysics
      Frankfurt, Hesse, Germany