TY - JOUR A1 - Blavatska, Viktoria A1 - Metzler, Ralf T1 - Conformational properties of complex polymers: rosette versus star-like structures JF - Journal of physics : A, Mathematical and theoretical N2 - Multiple loop formation in polymer macromolecules is an important feature of the chromatin organization and DNA compactification in the nuclei. We analyse the size and shape characteristics of complex polymer structures, containing in general f(1) loops (petals) and f(2) linear chains (branches). Within the frames of continuous model of Gaussian macromolecule, we apply the path integration method and obtain the estimates for gyration radius R-g and asphericity (A) over cap of typical conformation as functions of parameters f(1), f(2). In particular, our results qualitatively reveal the extent of anisotropy of star-like topologies as compared to the rosette structures of the same total molecular weight. KW - polymers KW - path integration KW - conformational properties Y1 - 2015 U6 - https://doi.org/10.1088/1751-8113/48/13/135001 SN - 1751-8113 SN - 1751-8121 VL - 48 IS - 13 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Couturier, Jean-Philippe A1 - Sütterlin, Martin A1 - Laschewsky, André A1 - Hettrich, Cornelia A1 - Wischerhoff, Erik T1 - Responsive Inverse Opal Hydrogels for the Sensing of Macromolecules JF - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition N2 - Dual responsive inverse opal hydrogels were designed as autonomous sensor systems for (bio)macromolecules, exploiting the analyte-induced modulation of the opal's structural color. The systems that are based on oligo(ethylene glycol) macromonomers additionally incorporate comonomers with various recognition units. They combine a coil-to-globule collapse transition of the LCST type with sensitivity of the transition temperature toward molecular recognition processes. This enables the specific detection of macromolecular analytes, such as glycopolymers and proteins, by simple optical methods. While the inverse opal structure assists the effective diffusion even of large analytes into the photonic crystal, the stimulus responsiveness gives rise to strong shifts of the optical Bragg peak of more than 100nm upon analyte binding at a given temperature. The systems' design provides a versatile platform for the development of easy-to-use, fast, and low-cost sensors for pathogens. KW - hydrogels KW - photonic crystals KW - polymers KW - responsive materials KW - sensors Y1 - 2015 U6 - https://doi.org/10.1002/anie.201500674 SN - 1433-7851 SN - 1521-3773 VL - 54 IS - 22 SP - 6641 EP - 6644 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Shin, Jaeoh A1 - Cherstvy, Andrey G. A1 - Kim, Won Kyu A1 - Metzler, Ralf T1 - Facilitation of polymer looping and giant polymer diffusivity in crowded solutions of active particles JF - New journal of physics : the open-access journal for physics N2 - We study the dynamics of polymer chains in a bath of self-propelled particles (SPP) by extensive Langevin dynamics simulations in a two-dimensional model system. Specifically, we analyse the polymer looping properties versus the SPP activity and investigate how the presence of the active particles alters the chain conformational statistics. We find that SPPs tend to extend flexible polymer chains, while they rather compactify stiffer semiflexible polymers, in agreement with previous results. Here we show that higher activities of SPPs yield a higher effective temperature of the bath and thus facilitate the looping kinetics of a passive polymer chain. We explicitly compute the looping probability and looping time in a wide range of the model parameters. We also analyse the motion of a monomeric tracer particle and the polymer's centre of mass in the presence of the active particles in terms of the time averaged mean squared displacement, revealing a giant diffusivity enhancement for the polymer chain via SPP pooling. Our results are applicable to rationalising the dimensions and looping kinetics of biopolymers at constantly fluctuating and often actively driven conditions inside biological cells or in suspensions of active colloidal particles or bacteria cells. KW - diffusion KW - active transport KW - polymers Y1 - 2015 U6 - https://doi.org/10.1088/1367-2630/17/11/113008 SN - 1367-2630 VL - 17 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Liedel, Clemens A1 - Lewin, Christian A1 - Tsarkova, Larisa A1 - Böker, Alexander T1 - Reversible Switching of Block Copolymer Nanopatterns by Orthogonal Electric Fields JF - Small N2 - 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. KW - alignments KW - block copolymers KW - electric fields KW - reorientation KW - solvent vapor annealing KW - polymers Y1 - 2015 U6 - https://doi.org/10.1002/smll.201502259 SN - 1613-6810 SN - 1613-6829 VL - 11 IS - 45 SP - 6058 EP - 6064 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Vukicevic, Radovan A1 - Neffe, Axel T. A1 - Luetzow, Karola A1 - Pierce, Benjamin F. A1 - Lendlein, Andreas T1 - Conditional Ultrasound Sensitivity of Poly[(N-isopropylacrylamide)-co-(vinyl imidazole)] Microgels for Controlled Lipase Release JF - Macromolecular rapid communications N2 - Triggering the release of cargo from a polymer network by ultrasonication as an external, non-invasive stimulus can be an interesting concept for on-demand release. Here, it is shown that, in pH-and thermosensitive microgels, the ultrasound sensitivity of the polymer network depends on the external conditions. Crosslinked poly[(N-isopropylacrylamide)-co-(vinyl imidazole)] microgels showed a volume phase transition temperature (VPTT) of 25-50 degrees C, which increases with decreasing pH. Above the VPTT the polymer chains are collapsed, while below VPTT they are extended. Only in the case of maximum observed swelling, where the polymer chains are expanded, the microgels are mechanically fragmented through ultrasonication. In contrast, when the polymer chains are partially collapsed it is not possible to manipulate the microgels by ultrasound. Additionally, the ultrasound-induced on-demand release of wheat germ lipase from the microgels could be demonstrated successfully. The principle of conditional ultrasound sensitivity is likely to be general and can be used for selection of matrix-cargo combinations. KW - ultrasound KW - polymers KW - microgels KW - lipase release KW - controlled release KW - thermoresponsive polymers KW - biomaterials Y1 - 2015 U6 - https://doi.org/10.1002/marc.201500311 SN - 1022-1336 SN - 1521-3927 VL - 36 IS - 21 SP - 1891 EP - 1896 PB - Wiley-VCH CY - Weinheim ER -