TY - JOUR A1 - Wagner, Tom A1 - Lazar, Jaroslav A1 - Schnakenberg, Uwe A1 - Böker, Alexander T1 - In situ Electrothemical Impedance Spectroscopy of Electrostatically Driven Selective Gold Nanoparticle Adsorption on Block Copolymer Lamellae JF - Trials N2 - Electrostatic attraction between charged nano particles and oppositely charged nanopatterned polymeric films enables tailored structuring of functional nanoscopic surfaces. The bottom-up fabrication of organic/inorganic composites for example bears promising potential toward cheap fabrication of catalysts, optical sensors, and the manufacture of miniaturized electric circuitry. However, only little is known about the time-dependent adsorption behavior and the electronic or ionic charge transfer in the film bulk and at interfaces during nanoparticle assembly via electrostatic interactions. In situ electrochemical impedance spectroscopy (EIS) in combination with a microfluidic system for fast and reproducible liquid delivery was thus applied to monitor the selective deposition of negatively charged gold nanoparticles on top of positively charged poly(2-vinylpyridinium) (qP2VP) domains of phase separated lamellar poly(styrene)-block-poly(2-vinylpyridinium) (PS-b-qP2VP) diblock copolymer thin films. The acquired impedance data delivered information with respect to interfacial charge alteration, ionic diffusion, and the charge dependent nanoparticle adsorption kinetics, considering this yet unexplored system. We demonstrate that the selective adsorption of negatively charged gold nanoparticles (AuNPs) on positively charged qP2VP domains of lamellar PS-b-qP2VP thin films can indeed be tracked by EIS. Moreover, we show that the nanoparticle adsorption kinetics and the nanoparticle packing density are functions of the charge density in the qP2VP domains. KW - impedance spectroscopy KW - block copolymers KW - nanoparticles KW - electrostatics KW - adsorption kinetics Y1 - 2016 U6 - https://doi.org/10.1021/acsami.6b07708 SN - 1944-8244 VL - 8 SP - 27282 EP - 27290 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Zhou, Qihui A1 - Wuennemann, Patrick A1 - Kuhn, Philipp Till A1 - de Vries, Joop A1 - Helmin, Marta A1 - Böker, Alexander A1 - van Kooten, Theo G. A1 - van Rijn, Patrick T1 - Mechanical Properties of Aligned Nanotopologies for Directing Cellular Behavior JF - Advanced materials interfaces N2 - Tailoring cell–surface interactions is important for the of design medical implants as well as regenerative medicine and tissue engineering materials. Here the single parameter system is transcended via translating hard nanotopology into soft polymeric hydrogel structures via hydrogel imprinting lithography. The response of these cells to the nanotopology of the same dimensions but with different mechanical properties displays unexpected behavior between “hard” tissue cells and “soft” tissue cells. Y1 - 2016 U6 - https://doi.org/10.1002/admi.201600275 SN - 2196-7350 VL - 3 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Liu, Bing A1 - Böker, Alexander T1 - Measuring rotational diffusion of colloidal spheres with confocal microscopy JF - Soft matter N2 - We report an experimental method to measure the translational and rotational dynamics of colloidal spheres in three dimensions with confocal microscopy and show that the experimental values reasonably agree with the theoretical values. This method can be extended to study rotational dynamics in concentrated colloidal systems and complex bio-systems. Y1 - 2016 U6 - https://doi.org/10.1039/c6sm01082b SN - 1744-683X SN - 1744-6848 VL - 12 SP - 6033 EP - 6037 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Charan, Himanshu A1 - Kinzel, Julia A1 - Glebe, Ulrich A1 - Anand, Deepak A1 - Garakani, Tayebeh Mirzaei A1 - Zhu, Leilei A1 - Bocola, Marco A1 - Schwaneberg, Ulrich A1 - Böker, Alexander T1 - Grafting PNIPAAm from beta-barrel shaped transmembrane nanopores JF - Biomaterials : biomaterials reviews online N2 - The research on protein-polymer conjugates by grafting from the surface of proteins has gained significant interest in the last decade. While there are many studies with globular proteins, membrane proteins have remained untouched to the best of our knowledge. In this study, we established the conjugate formation with a class of transmembrane proteins and grow polymer chains from the ferric hydroxamate uptake protein component A (FhuA; a beta-barrel transmembrane protein of Escherichia coli). As the lysine residues of naturally occurring FhuA are distributed over the whole protein, FhuA was reengineered to have up to 11 lysines, distributed symmetrically in a rim on the membrane exposed side (outside) of the protein channel and exclusively above the hydrophobic region. Reengineering of FhuA ensures a polymer growth only on the outside of the beta-barrel and prevents blockage of the channel as a result of the polymerization. A water-soluble initiator for controlled radical polymerization (CRP) was consecutively linked to the lysine residues of FhuA and N-isopropylacrylamide (NIPAAm) polymerized under copper mediated CRP conditions. The conjugate formation was analyzed by using MALDI-ToF mass spectrometry, SDS-PAGE, circular dichroism spectroscopy, analytical ultracentrifugation, dynamic light scattering, transmission electron microscopy and size exclusion chromatography. Such conjugates combine the specific functions of the transmembrane proteins, like maintaining membrane potential gradients or translocation of substrates with the unique properties of synthetic polymers such as temperature and pH stimuli handles. FhuA-PNIPAAm conjugates will serve as functional nanosized building blocks for applications in targeted drug delivery, self-assembly systems, functional membranes and transmembrane protein gated nanoreactors. (C) 2016 Elsevier Ltd. All rights reserved. KW - Transmembrane protein KW - FhuA KW - Protein-polymer conjugate KW - Grafting-from polymerization KW - NIPAAm KW - BBTP Y1 - 2016 U6 - https://doi.org/10.1016/j.biomaterials.2016.08.033 SN - 0142-9612 SN - 1878-5905 VL - 107 SP - 115 EP - 123 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kathrein, Christine C. A1 - Bai, Wubin A1 - Nunns, Adam A1 - Gwyther, Jessica A1 - Manners, Ian A1 - Böker, Alexander A1 - Tsarkova, Larisa A1 - Ross, Caroline A. T1 - Electric field manipulated nanopatterns in thin films of metalorganic 3-miktoarm star terpolymers JF - Soft matter N2 - We report the effect of electric field on the morphological transitions and ordering behavior of polyferrocenylethylmethylsilane block (PFEMS)-containing copolymers. By analyzing structures in solvent-annealed films of metalorganic sphere-and cylinder-forming diblock copolymers, as well as of 3-miktoarm polyisoprene-arm-polystyrene-arm-PFEMS (3 mu-ISF) terpolymers, we decouple two types of responses to the electric field: morphological transformations as a result of an increase in the volume fraction of the PFEMS block by oxidation of the ferrocenyl groups, and the orientation of the dielectric interfaces of microdomains parallel to the electric field vector. In the case of 3m-ISF, the former effect dominates at high electric field strengths which results in an unexpected cylinder-to-sphere transition, leading to a well-ordered hexagonal dot pattern. Our results demonstrate multiple tunability of ordered microdomain morphologies, suggesting future applications in nanofabrication and surface patterning. Y1 - 2016 U6 - https://doi.org/10.1039/c6sm00451b SN - 1744-683X SN - 1744-6848 VL - 12 SP - 4866 EP - 4874 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Kathrein, Christine C. A1 - Pester, Christian A1 - Ruppel, Markus A1 - Jung, Maike A1 - Zimmermann, Marc A1 - Böker, Alexander T1 - Reorientation mechanisms of block copolymer/CdSe quantum dot composites under application of an electric field JF - Soft matter N2 - Time- and temperature-resolved in situ birefringence measurements were applied to analyze the effect of nanoparticles on the electric field-induced alignment of a microphase separated solution of poly(styrene)-block-poly(isoprene) in toluene. Through the incorporation of isoprene-confined CdSe quantum dots the reorientation behavior is altered. Particle loading lowers the order-disorder transition temperature, and increases the defect density, favoring nucleation and growth as an alignment mechanism over rotation of grains. The temperature dependent alteration in the reorientation mechanism is analyzed via a combination of birefringence and synchrotron SAXS. The detailed understanding of the effect of nanoparticles on the reorientation mechanism is an important prerequisite for optimization of electricfield-induced alignment of block copolymer/nanoparticle composites where the block copolymer guides the nanoparticle self-assembly into anisotropic structures. Y1 - 2016 U6 - https://doi.org/10.1039/c6sm01073c SN - 1744-683X SN - 1744-6848 VL - 12 SP - 8417 EP - 8424 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Richter, Marina Juliane A1 - Schulz, Alexander A1 - Subkowski, Thomas A1 - Böker, Alexander T1 - Adsorption and rheological behavior of an amphiphilic protein at oil/water interfaces JF - Journal of colloid and interface science N2 - Hydrophobins are highly surface active proteins which self-assemble at hydrophilic-hydrophobic interfaces into amphipathic membranes. We investigate hydrophobin self-assembly at oil/water interfaces to deepen the understanding of protein behavior in order to improve our biomimetic synthesis. Therefore, we carried out pendant drop measurements of hydrophobin stabilized oil/water systems determining the time-dependent IFT and the dilatational rheology with additional adaptation to the Serrien protein model. We show that the class I hydrophobin H*Protein B adsorbs at an oil/water interface where it forms a densely-packed interfacial protein layer, which dissipates energy during droplet oscillation. Furthermore, the interfacial protein layer exhibits shear thinning behavior. (C) 2016 Elsevier Inc. All rights reserved. KW - Hydrophobin KW - Self-assembly KW - Pendant drop tensiometry KW - IFT KW - Rheology Y1 - 2016 U6 - https://doi.org/10.1016/j.jcis.2016.06.062 SN - 0021-9797 SN - 1095-7103 VL - 479 SP - 199 EP - 206 PB - Elsevier CY - San Diego ER - TY - JOUR A1 - Hiltl, Stephanie A1 - Böker, Alexander T1 - Wetting Phenomena on (Gradient) Wrinkle Substrates JF - Langmuir N2 - We characterize the wetting behavior of nano structured wrinkle and gradient wrinkle substrates. Different contact angles on both sides of a water droplet after deposition on a gradient sample induce the self-propelled motion of the liquid toward smaller wrinkle dimensions. The droplet motion is self-limited by the contact angles balancing out. Because of the correlation between droplet motion and contact angles, we investigate the wetting behavior of wrinkle substrates with constant dimensions (wavelengths of 400-1200 nm). Contact angles of water droplets on those substrates increase with increasing dimensions of the underlying substrate. The results are independent of the two measurement directions, parallel and perpendicular to the longitudinal axis of the nanostructure. The presented findings may be considered for designing microfluidic or related devices and initiate ideas for the development of further wrinkle applications. Y1 - 2016 U6 - https://doi.org/10.1021/acs.langmuir.6b02364 SN - 0743-7463 VL - 32 SP - 8882 EP - 8888 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Wu, Lei A1 - Glebe, Ulrich A1 - Böker, Alexander T1 - Synthesis of Hybrid Silica Nanoparticles Densely Grafted with Thermo and pH Dual-Responsive Brushes via Surface-Initiated ATRP JF - Macromolecules : a publication of the American Chemical Society Y1 - 2016 U6 - https://doi.org/10.1021/acs.macromol.6b01792 SN - 0024-9297 SN - 1520-5835 VL - 49 SP - 9586 EP - 9596 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Wuennemann, Patrick A1 - Noyong, Michael A1 - Kreuels, Klaus A1 - Bruex, Roland A1 - Gordiichuk, Pavlo A1 - van Rijn, Patrick A1 - Plamper, Felix A. A1 - Simon, Ulrich A1 - Böker, Alexander T1 - Microstructured Hydrogel Templates for the Formation of Conductive Gold Nanowire Arrays JF - Macromolecular rapid communications N2 - Microstructured hydrogel allows for a new template-guided method to obtain conductive nanowire arrays on a large scale. To generate the template, an imprinting process is used in order to synthesize the hydrogel directly into the grooves of wrinkled polydimethylsiloxane (PDMS). The resulting poly(N-vinylimidazole)-based hydrogel is defined by the PDMS stamp in pattern and size. Subsequently, tetrachloroaurate(III) ions from aqueous solution are coordinated within the humps of the N-vinylimidazole-containing polymer template and reduced by air plasma. After reduction and development of the gold, to achieve conductive wires, the extension perpendicular to the long axis (width) of the gold strings is considerably reduced compared to the dimension of the parental hydrogel wrinkles (from approximate to 1 mu m down to 200-300 nm). At the same time, the wire-to-wire distance and the overall length of the wires is preserved. The PDMS templates and hydrogel structures are analyzed with scanning force microscopy (SFM) and the gold structures via scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy. The conductivity measurements of the gold nanowires are performed in situ in the SEM, showing highly conductive gold leads. Hence, this method can be regarded as a facile nonlithographic top-down approach from micrometer-sized structures to nanometer-sized features. KW - 1D structures KW - Au nanoarrays KW - microgel KW - nanoimprint KW - lithography KW - thin films Y1 - 2016 U6 - https://doi.org/10.1002/marc.201600287 SN - 1022-1336 SN - 1521-3927 VL - 37 SP - 1446 EP - 1452 PB - Wiley-VCH CY - Weinheim ER -