@misc{WuGlebeBoeker2015,
  author    = {Wu, Lei and Glebe, Ulrich and B{\"o}ker, Alexander},
  title     = {Surface-initiated controlled radical polymerizations from silica nanoparticles, gold nanocrystals, and bionanoparticles},
  series = {Polymer Chemistry},
  volume    = {6},
  journal   = {Polymer Chemistry},
  number    = {29},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1759-9954},
  doi       = {10.1039/c5py00525f},
  pages     = {5143 -- 5184},
  year      = {2015},
  abstract  = {In recent years, core/shell nanohybrids containing a nanoparticle core and a distinct surrounding shell of polymer brushes have received extensive attention in nanoelectronics, nanophotonics, catalysis, nanopatterning, drug delivery, biosensing, and many others. From the large variety of existing polymerization methods on the one hand and strategies for grafting onto nanoparticle surfaces on the other hand, the combination of grafting-from with controlled radical polymerization (CRP) techniques has turned out to be the best suited for synthesizing these well-defined core/shell nanohybrids and is known as surface-initiated CRP. Most common among these are surface-initiated atom transfer radical polymerization (ATRP), surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization, and surface-initiated nitroxide-mediated polymerization (NMP). This review highlights the state of the art of growing polymers from nanoparticles using surface-initiated CRP techniques. We focus on mechanistic aspects, synthetic procedures, and the formation of complex architectures as well as novel properties. From the vast number of examples of nanoparticle/polymer hybrids formed by surface-initiated CRP techniques, we present nanohybrid formation from the particularly important and most studied silica nanoparticles, gold nanocrystals, and proteins which can be regarded as bionanoparticles.},
  language  = {en}
}
@article{PesterSchmidtRuppeletal.2015,
  author    = {Pester, Christian W. and Schmidt, Kristin and Ruppel, Markus and Schoberth, Heiko G. and B{\"o}ker, Alexander},
  title     = {Electric-Field-Induced Order-Order Transition from Hexagonally Perforated Lamellae to Lamellae},
  series = {Macromolecules : a publication of the American Chemical Society},
  volume    = {48},
  journal   = {Macromolecules : a publication of the American Chemical Society},
  number    = {17},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {0024-9297},
  doi       = {10.1021/acs.macromol.5b01336},
  pages     = {6206 -- 6213},
  year      = {2015},
  abstract  = {Block copolymers form a variety of microphase morphologies due to their ability to phase separate. The hexagonally perforated lamellar (HPL) morphology represents an unusually long-lived, nonequilibrium transient structure between lamellar and cylindrical phases. We present a detailed study of a concentrated, HPL-forming poly(styrene-b-isoprene) diblock copolymer solution in toluene in the presence of an electric field. We will show that this phase is readily aligned by a moderate electric field and provide experimental evidence for an electric-field-induced order order transition toward the lamellar phase under sufficiently strong fields. This process is shown to be fully reversible as lamellar perforations reconnect immediately upon secession of the external stimulus, recovering highly aligned perforated lamellae.},
  language  = {en}
}
@article{MergelWuennemannSimonetal.2015,
  author    = {Mergel, Olga and Wuennemann, Patrick and Simon, Ulrich and B{\"o}ker, Alexander and Plamper, Felix A.},
  title     = {Microgel Size Modulation by Electrochemical Switching},
  series = {Chemistry of materials : a publication of the American Chemical Society},
  volume    = {27},
  journal   = {Chemistry of materials : a publication of the American Chemical Society},
  number    = {21},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {0897-4756},
  doi       = {10.1021/acs.chemmater.5b02740},
  pages     = {7306 -- 7312},
  year      = {2015},
  abstract  = {In this work we present the first e-microgel, whose size can be adjusted by application of an electrochemical potential, as seen by dynamic light scattering (3D-DLS in dependence of equilibrium potential) and scanning force microscopy (SFM). Hereby, polyelectrolyte microgels with attracted electroactive counterions provide an effective platform for the manipulation of the microgel size by electrochemical means. The reversible switching of guest molecules, namely, hexacyanoferrates, between oxidized ferricyanide [Fe(CN)(6)](3-) and reduced ferrocyanide [Fe(CN)(6)](4-), influences the cationic host microgel, poly(N-isopropylacrylamide-co-methacrylamidopropyltrimethylammonium chloride) P(NIPAM-co-MAPTAC), and hence the swelling properties of the microgel. The combination of thermo- and redox-responsiveness in one particle leads to a novel type of multistimuli responsive material. In addition, the use of hydrodynamic voltammetry detects directly the preferred uptake of ferricyanide and enables the determination of the nominal charge ratio (ncr) between microgel and entrapped counterions at different states of switching. Further, electrochemical impedance spectroscopy allows a more detailed mechanistic insight into the microgel modulation.},
  language  = {en}
}
@article{LiedelLewinTsarkovaetal.2015,
  author    = {Liedel, Clemens and Lewin, Christian and Tsarkova, Larisa and B{\"o}ker, Alexander},
  title     = {Reversible Switching of Block Copolymer Nanopatterns by Orthogonal Electric Fields},
  series = {Small},
  volume    = {11},
  journal   = {Small},
  number    = {45},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1613-6810},
  doi       = {10.1002/smll.201502259},
  pages     = {6058 -- 6064},
  year      = {2015},
  abstract  = {It is demonstrated that the orientation of striped patterns can be reversibly switched between two perpendicular in-plane orientations upon exposure to electric fields. The results on thin films of symmetric polystyrene-block-poly(2-vinyl pyridine) polymer in the intermediate segregation regime disclose two types of reorientation mechanisms from perpendicular to parallel relative to the electric field orientation. Domains orient via grain rotation and via formation of defects such as stretched undulations and temporal phase transitions. The contribution of additional fields to the structural evolution is also addressed to elucidate the generality of the observed phenomena. In particular solvent effects are considered. This study reveals the stabilization of the meta-stable in-plane oriented lamella due to sequential swelling and quenching of the film. Further, the reorientation behavior of lamella domains blended with selective nanoparticles is addressed, which affect the interfacial tensions of the blocks and hence introduce another internal field to the studied system. Switching the orientation of aligned block copolymer patterns between two orthogonal directions may open new applications of nanomaterials as switchable electric nanowires or optical gratings.},
  language  = {en}
}
@article{KathreinKipnusuKremeretal.2015,
  author    = {Kathrein, Christine C. and Kipnusu, Wycliffe K. and Kremer, Friedrich and B{\"o}ker, Alexander},
  title     = {Birefringence Analysis of the Effect of Electric Fields on the Order-Disorder Transition Temperature of Lamellae Forming Block Copolymers},
  series = {Macromolecules : a publication of the American Chemical Society},
  volume    = {48},
  journal   = {Macromolecules : a publication of the American Chemical Society},
  number    = {10},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {0024-9297},
  doi       = {10.1021/acs.macromol.5b00512},
  pages     = {3354 -- 3359},
  year      = {2015},
  abstract  = {A detailed birefringence analysis of the effect of strong dc electric fields on the order-disorder transition temperature (T-ODT) of lamella forming block copolymers is reported. The setup presented here enabled the measurement of the T-ODT with high temperature resolution while the birefringence measurements were nondestructive and straightforward compared to alternative methods. A downward shift in the transition temperature was found for all samples upon application of the electric field. The data indicate that the dominating parameter that evokes the mixing of block copolymers when exposed to electric fields is the difference in dielectric permittivity Delta epsilon between the block copolymer constituents. The extent to which the T-ODT is shifted is furthermore influenced by the degree of polymerization N. Shifts in the transition temperature of up to 7 degrees C were found upon application of an electric field of 5 kV/mm.},
  language  = {en}
}
@article{KathreinBaiCurrivanIncorviaetal.2015,
  author    = {Kathrein, Christine C. and Bai, Wubin and Currivan-Incorvia, Jean Anne and Liontos, George and Ntetsikas, Konstantinos and Avgeropoulos, Apostolos and B{\"o}ker, Alexander and Tsarkova, Larisa and Ross, Caroline A.},
  title     = {Combining Graphoepitaxy and Electric Fields toward Uniaxial Alignment of Solvent-Annealed Polystyrene-b-Poly(dimethylsiloxane) Block Copolymers},
  series = {Chemistry of materials : a publication of the American Chemical Society},
  volume    = {27},
  journal   = {Chemistry of materials : a publication of the American Chemical Society},
  number    = {19},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {0897-4756},
  doi       = {10.1021/acs.chemmater.5b03354},
  pages     = {6890 -- 6898},
  year      = {2015},
  abstract  = {We report a combined directing effect of the simultaneously applied graphoepitaxy and electric field on the self-assembly of cylinder forming polystyrene-b-poly(dimethylsiloxane) block copolymer in thin films. A correlation length of up to 20 mu m of uniaxial ordered striped patterns is an order of magnitude greater than that produced by either graphoepitaxy or electric field alignment alone and is achieved at reduced annealing times. The angle between the electric field direction and the topographic guides as well as the dimensions of the trenches affected both the quality of the ordering and the direction of the orientation of cylindrical domains: parallel or perpendicular to the topographic features. We quantified the interplay between the electric field and the geometry of the topographic structures by constructing the phase diagram of microdomain orientation. This combined approach allows the fabrication of highly ordered block copolymer structures using macroscopically prepatterned photolithographic substrates.},
  language  = {en}
}