@article{WeisHessKircheretal.2019, author = {Weis, Philipp and Hess, Andreas and Kircher, Gunnar and Huang, Shilin and Auernhammer, G{\"u}nter K. and Koynov, Kaloian and Butt, Hans-J{\"u}rgen and Wu, Si}, title = {Effects of Spacers on Photoinduced Reversible Solid-to-Liquid Transitions of Azobenzene-Containing Polymers}, series = {Chemistry - a European journal}, volume = {25}, journal = {Chemistry - a European journal}, number = {46}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0947-6539}, doi = {10.1002/chem.201902273}, pages = {10946 -- 10953}, year = {2019}, abstract = {Photoisomerization in some azobenzene-containing polymers (azopolymers) results in reversible solid-to-liquid transitions because trans- and cis-azopolymers have different glass transition temperatures. This property enables photoinduced healing and processing of azopolymers with high spatiotemporal resolution. However, a general lack of knowledge about the influence of the polymer structure on photoinduced reversible solid-to-liquid transitions hinders the design of such novel polymers. Herein, the synthesis and photoresponsive behavior of new azopolymers with different lengths of spacers between the polymer backbone and the azobenzene group on the side chain are reported. Azopolymers with no and 20 methylene spacers did not show photoinduced solid-to-liquid transitions. Azopolymers with 6 or 12 methylene spacers showed photoinduced solid-to-liquid transitions. This study demonstrates that spacers are essential for azopolymers with photoinduced reversible solid-to-liquid transitions, and thus, gives an insight into how to design azopolymers for photoinduced healing and processing.}, language = {en} } @article{VukicevicNeffeLuetzowetal.2015, author = {Vukicevic, Radovan and Neffe, Axel T. and Luetzow, Karola and Pierce, Benjamin F. and Lendlein, Andreas}, title = {Conditional Ultrasound Sensitivity of Poly[(N-isopropylacrylamide)-co-(vinyl imidazole)] Microgels for Controlled Lipase Release}, series = {Macromolecular rapid communications}, volume = {36}, journal = {Macromolecular rapid communications}, number = {21}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1336}, doi = {10.1002/marc.201500311}, pages = {1891 -- 1896}, year = {2015}, abstract = {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.}, language = {en} } @phdthesis{Steyrleuthner2014, author = {Steyrleuthner, Robert}, title = {Korrelation von Struktur, optischen Eigenschaften und Ladungstransport in einem konjugierten Naphthalindiimid-Bithiophen Copolymer mit herausragender Elektronenmobilit{\"a}t}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-71413}, school = {Universit{\"a}t Potsdam}, year = {2014}, abstract = {Organische Halbleiter besitzen neue, bemerkenswerte Materialeigenschaften, die sie f{\"u}r die grundlegende Forschung wie auch aktuelle technologische Entwicklung (bsw. org. Leuchtdioden, org. Solarzellen) interessant werden lassen. Aufgrund der starken konformative Freiheit der konjugierten Polymerketten f{\"u}hrt die Vielzahl der m{\"o}glichen Anordnungen und die schwache intermolekulare Wechselwirkung f{\"u}r gew{\"o}hnlich zu geringer struktureller Ordnung im Festk{\"o}rper. Die Morphologie hat gleichzeitig direkten Einfluss auf die elektronische Struktur der organischen Halbleiter, welches sich meistens in einer deutlichen Reduktion der Ladungstr{\"a}gerbeweglichkeit gegen{\"u}ber den anorganischen Verwandten zeigt. So stellt die Beweglichkeit der Ladungen im Halbleiter einen der limitierenden Faktoren f{\"u}r die Leistungsf{\"a}higkeit bzw. den Wirkungsgrad von funktionellen organischen Bauteilen dar. Im Jahr 2009 wurde ein neues auf Naphthalindiimid und Bithiophen basierendes Dornor/Akzeptor Copolymer vorgestellt [P(NDI2OD‑T2)], welches sich durch seine außergew{\"o}hnlich hohe Ladungstr{\"a}germobilit{\"a}t auszeichnet. In dieser Arbeit wird die Ladungstr{\"a}germobilit{\"a}t in P(NDI2OD‑T2) bestimmt, und der Transport durch eine geringe energetischer Unordnung charakterisiert. Obwohl dieses Material zun{\"a}chst als amorph beschrieben wurde zeigt eine detaillierte Analyse der optischen Eigenschaften von P(NDI2OD‑T2), dass bereits in L{\"o}sung geordnete Vorstufen supramolekularer Strukturen (Aggregate) existieren. Quantenchemische Berechnungen belegen die beobachteten spektralen {\"A}nderungen. Mithilfe der NMR-Spektroskopie kann die Bildung der Aggregate unabh{\"a}ngig von optischer Spektroskopie best{\"a}tigt werden. Die Analytische Ultrazentrifugation an P(NDI2OD‑T2) L{\"o}sungen legt nahe, dass sich die Aggregation innerhalb der einzelnen Ketten unter Reduktion des hydrodynamischen Radius vollzieht. Die Ausbildung supramolekularen Strukturen nimmt auch eine signifikante Rolle bei der Filmbildung ein und verhindert gleichzeitig die Herstellung amorpher P(NDI2OD‑T2) Filme. Durch chemische Modifikation der P(NDI2OD‑T2)-Kette und verschiedener Prozessierungs-Methoden wurde eine {\"A}nderung des Kristallinit{\"a}tsgrades und gleichzeitig der Orientierung der kristallinen Dom{\"a}nen erreicht und mittels R{\"o}ntgenbeugung quantifiziert. In hochaufl{\"o}senden Elektronenmikroskopie-Messungen werden die Netzebenen und deren Einbettung in die semikristallinen Strukturen direkt abgebildet. Aus der Kombination der verschiedenen Methoden erschließt sich ein Gesamtbild der Nah- und Fernordnung in P(NDI2OD‑T2). {\"U}ber die Messung der Elektronenmobilit{\"a}t dieser Schichten wird die Anisotropie des Ladungstransports in den kristallographischen Raumrichtungen von P(NDI2OD‑T2) charakterisiert und die Bedeutung der intramolekularen Wechselwirkung f{\"u}r effizienten Ladungstransport herausgearbeitet. Gleichzeitig wird deutlich, wie die Verwendung von gr{\"o}ßeren und planaren funktionellen Gruppen zu h{\"o}heren Ladungstr{\"a}germobilit{\"a}ten f{\"u}hrt, welche im Vergleich zu klassischen semikristallinen Polymeren weniger sensitiv auf die strukturelle Unordnung im Film sind.}, language = {de} } @phdthesis{Stephan2007, author = {Stephan, Niels}, title = {Ph{\"a}nomenologische Untersuchungen zur Feuchteempfindlichkeit der elektrischen Eigenschaften von d{\"u}nnen Polymerfilmen und deren Verwendung f{\"u}r neuartige Feuchtesensoren}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-13853}, school = {Universit{\"a}t Potsdam}, year = {2007}, abstract = {Ziel dieser Arbeit ist die ph{\"a}nomenologische Untersuchung der Feuchteempfindlichkeit der elektrischen Eigenschaften d{\"u}nner Polymerschichten. Diese Untersuchungen stellen gleichzeitig Vorarbeiten zur Entwicklung von Prototypen von zwei polymeren D{\"u}nnschicht-Feuchtesensoren dar, die sich durch die spezielle Auswahl der feuchtesensitiven Materialien jeweils durch eine besondere Eigenschaft gegen{\"u}ber kommerziellen Massenprodukten auszeichnen. Ziel der Entwicklungsarbeiten f{\"u}r den ersten Prototypen war die Konstruktion eines schnellen Feuchtesensors, der pl{\"o}tzliche und sprunghafte Feuchte{\"a}nderungen in der umgebenden Atmosph{\"a}re m{\"o}glichst rasch detektieren kann. Daf{\"u}r wurden d{\"u}nne Schichten von Poly-DADMAC auf Interdigitalstrukturen aufgebracht, die einen m{\"o}glichst direkten Kontakt zwischen feuchtesensitiver Schicht und umgebender, feuchter Atmosph{\"a}re gew{\"a}hrleisten. Als Messgr{\"o}ßen dienten die Wechselstromgr{\"o}ßen Widerstand und Kapazit{\"a}t der Schichten. Die Feuchtekennlinien der Schichten zeigen gute Konstanz und hohe Reproduzierbarkeit. Der Widerstand der Schichten {\"a}ndert sich durch den Einfluss von Feuchte je nach Schichtdicke um 3 bis 5 Gr{\"o}ßenordnungen und eignet sich als Messgr{\"o}ße f{\"u}r die Feuchtigkeit im gesamten Feuchtebereich. Die Hysterese der Filme konnte auf kleiner als 2,5\% r.F. bestimmt werden, die Reproduzierbarkeit auf besser als 1\% r.F. Die Ansprechzeit der Schichten l{\"a}sst sich schichtdickenabh{\"a}ngig zu 1 bis 10 Sekunden bestimmen. Hierbei zeigen besonders die d{\"u}nnen Schichten kurze Ansprechzeiten. Zielstellung f{\"u}r den zweiten Feuchtesensor war die Entwicklung eines Prototypen, dessen sensitive Schicht sich biostatisch und biozid verh{\"a}lt, so dass er in biotischen Umgebungen eingesetzt werden kann. Es wurden f{\"u}nf Polysulfobetaine synthetisiert, deren Biozidit{\"a}t und Biostatik mit dem Kontakttest nach R{\"o}nnpagel, dem ISO846-Test und Abbautests bestimmt wurde. Zwei Polymere - Poly-DMMAAPS (BT2) und Poly-[MSA-Styren-Sulfobetain] (BT5) - erwiesen sich als ausreichend biozid und biostatisch. Schichten dieser Polymere wurden auf Interdigitalstrukturen aufgezogen, anschließend wurden die Kennlinien dieser Proben aufgenommen. Die Messwerte zeigen f{\"u}r beide Polymere gute Konstanz und eine hohe Reproduzierbarkeit. BT2-Proben sind zwischen 20\% und 80\% r.F. besonders empfindlich und zeigen {\"u}ber einen Monat keine Langzeitdrift. Vernetzte Proben zeigen bis 50°C keinen temperaturbedingten Abfall der Feuchteempfindlichkeit. Der Einsatz vernetzter BT5-Schichten als kapazitiver Feuchtesensor ist bis etwa 70°C m{\"o}glich, die Schichten sind selbst nach Lagerung im Hochvakuum und mehrfacher Betauung stabil. Damit liegen zwei funktionsf{\"a}hige Prototypen von Feuchtesensoren vor, f{\"u}r die die meisten Kennwerte denen von vergleichbaren kommerziellen Feuchtesensoren entsprechen. Gleichzeitig zeichnen sie sich aber durch eine sehr niedrige Ansprechzeit bzw. eine ausreichende Lebensdauer unter biotischen Bedingungen aus.}, language = {de} } @article{ShinCherstvyMetzler2014, author = {Shin, Jaeoh and Cherstvy, Andrey G. and Metzler, Ralf}, title = {Mixing and segregation of ring polymers: spatial confinement and molecular crowding effects}, series = {New journal of physics : the open-access journal for physics}, volume = {16}, journal = {New journal of physics : the open-access journal for physics}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1367-2630}, doi = {10.1088/1367-2630/16/5/053047}, pages = {19}, year = {2014}, abstract = {During the life cycle of bacterial cells the non-mixing of the two ring-shaped daughter genomes is an important prerequisite for the cell division process. Mimicking the environments inside highly crowded biological cells, we study the dynamics and statistical behavior of two flexible ring polymers in the presence of cylindrical confinement and crowding molecules. From extensive computer simulations we determine the degree of ring-ring overlap and the number of inter-monomer contacts for varying volume fractions phi of crowders. We also examine the entropic demixing of polymer rings in the presence of mobile crowders and determine the characteristic times of the internal polymer dynamics. Effects of the ring length on ring-ring overlap are also analyzed. In particular, on systematic variation of the fraction of crowding molecules, a (1 - phi)-scaling is found for the ring-ring overlap length along the cylinder axis, and a non-monotonic dependence of the 3D ring-ring contact number with a maximum at phi approximate to 0.2 is obtained. Our results demonstrate that polymer rings are demixed and separated by particular entropy-favourable partitioning of crowders along the axis of the cylindrical simulation box. These findings help to rationalize the implications of macromolecular crowding for circular DNA molecules in confined spaces inside bacteria as well as in localized cellular compartments inside eukaryotic cells.}, language = {en} } @article{ShinCherstvyKimetal.2015, author = {Shin, Jaeoh and Cherstvy, Andrey G. and Kim, Won Kyu and Metzler, Ralf}, title = {Facilitation of polymer looping and giant polymer diffusivity in crowded solutions of active particles}, series = {New journal of physics : the open-access journal for physics}, volume = {17}, journal = {New journal of physics : the open-access journal for physics}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1367-2630}, doi = {10.1088/1367-2630/17/11/113008}, pages = {12}, year = {2015}, abstract = {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.}, language = {en} } @phdthesis{Schattauer2010, author = {Schattauer, Sylvia}, title = {Hybride D{\"u}nnschicht-Solarzellen aus mesopor{\"o}sem Titandioxid und konjugierten Polymeren}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-52619}, school = {Universit{\"a}t Potsdam}, year = {2010}, abstract = {Das Ziel dieser Arbeit ist die Untersuchung der aktiven Komponenten und ihrer Wechselwirkungen in teilorganischen Hybrid-Solarzellen. Diese bestehen aus einer d{\"u}nnen Titandioxidschicht, kombiniert mit einer d{\"u}nnen Polymerschicht. Die Effizienz der Hybrid-Solarzellen wird durch die Lichtabsorption im Polymer, die Dissoziation der gebildeten Exzitonen an der aktiven Grenzfl{\"a}che zwischen TiO2 und Polymer, sowie durch Generation und Extraktion freier Ladungstr{\"a}ger bestimmt. Zur Optimierung der Solarzellen wurden grundlegende physikalische Wechselwirkungen zwischen den verwendeten Materialen sowie der Einfluss verschiedener Herstellungsparameter untersucht. Unter anderem wurden Fragen zum optimalen Materialeinsatz und Pr{\"a}parationsbedingungen beantwortet sowie grundlegende Einfl{\"u}sse wie Schichtmorphologie und Polymerinfiltration n{\"a}her betrachtet. Zun{\"a}chst wurde aus unterschiedlich hergestelltem Titandioxid (Akzeptor-Schicht) eine Auswahl f{\"u}r den Einsatz in Hybrid-Solarzellen getroffen. Kriterium war hierbei die unterschiedliche Morphologie aufgrund der Oberfl{\"a}chenbeschaffenheit, der Film-Struktur, der Kristallinit{\"a}t und die daraus resultierenden Solarzelleneigenschaften. F{\"u}r die anschließenden Untersuchungen wurden mesopor{\"o}se TiO2-Filme aus einer neuen Nanopartikel-Synthese, welche es erlaubt, kristalline Partikel schon w{\"a}hrend der Synthese herzustellen, als Elektronenakzeptor und konjugierte Polymere auf Poly(p-Phenylen-Vinylen) (PPV)- bzw. Thiophenbasis als Donatormaterial verwendet. Bei der thermischen Behandlung der TiO2-Schichten erfolgt eine temperaturabh{\"a}ngige {\"A}nderung der Morphologie, jedoch nicht der Kristallstruktur. Die Auswirkungen auf die Solarzelleneigenschaften wurden dokumentiert und diskutiert. Um die Vorteile der Nanopartikel-Synthese, die Bildung kristalliner TiO2-Partikel bei tiefen Temperaturen, nutzen zu k{\"o}nnen, wurden erste Versuche zur UV-Vernetzung durchgef{\"u}hrt. Neben der Beschaffenheit der Oxidschicht wurde auch der Einfluss der Polymermorphologie, bedingt durch L{\"o}sungsmittelvariation und Tempertemperatur, untersucht. Hierbei konnte gezeigt werden, dass u.a. die Viskosit{\"a}t der Polymerl{\"o}sung die Infiltration in die TiO2-Schicht und dadurch die Effizienz der Solarzelle beeinflusst. Ein weiterer Ansatz zur Erh{\"o}hung der Effizienz ist die Entwicklung neuer lochleitender Polymere, welche m{\"o}glichst {\"u}ber einen weiten spektralen Bereich Licht absorbieren und an die Bandl{\"u}cke des TiO2 angepasst sind. Hierzu wurden einige neuartige Konzepte, z.B. die Kombination von Thiophen- und Phenyl-Einheiten n{\"a}her untersucht. Auch wurde die Sensibilisierung der Titandioxidschicht in Anlehnung an die h{\"o}heren Effizienzen der Farbstoffzellen in Betracht gezogen. Zusammenfassend konnten im Rahmen dieser Arbeit wichtige Einflussparameter auf die Funktion hybrider Solarzellen identifiziert und z.T. n{\"a}her diskutiert werden. F{\"u}r einige limitierende Faktoren wurden Konzepte zur Verbesserung bzw. Vermeidung vorgestellt.}, language = {de} } @phdthesis{LorenteSanchez2017, author = {Lorente S{\´a}nchez, Alejandro Jose}, title = {Synthesis of side-chain polystyrenes for all organic solution processed OLEDs}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-398006}, school = {Universit{\"a}t Potsdam}, pages = {xiv, 131}, year = {2017}, abstract = {In the present work side-chain polystyrenes were synthesized and characterized, in order to be applied in multilayer OLEDs fabricated by solution process techniques. Manufacture of optoelectronic devices by solution process techniques is meant to decrease significantly fabrication cost and allow large scale production of such devices. This dissertation focusses in three series, enveloped in two material classes. The two classes differ to each other in the type of charge transport exhibited, either ambipolar transport or electron transport. All materials were applied in all-organic solution processed green Ir-based devices. In the first part, a series of ambipolar host materials were developed to transport both charge types, holes and electrons, and be applied especially as matrix for green Ir-based emitters. It was possible to increase devices efficacy by modulating the predominant charge transport type. This was achieved by modification of molecules electron transport part with more electron-deficient heterocycles or by extending the delocalization of the LUMO. Efficiencies up to 28.9 cd/A were observed for all-organic solution-process three layer devices. In the second part, suitability of triarylboranes and tetraphenylsilanes as electron transport materials was studied. High triplet energies were obtained, up to 2.95 eV, by rational combination of both molecular structures. Although the combination of both elements had a low effect in materials electron transport properties, high efficiencies around 24 cd/A were obtained for the series in all-organic solution-processed two layer devices. In the last part, benzene and pyridine were chosen as the series electron-transport motif. By controlling the relative pyridine content (RPC) solubility into methanol was induced for polystyrenes with bulky side-chains. Materials with RPC ≥ 0.5 could be deposited orthogonally from solution without harming underlying layers. From the best of our knowledge, this is the first time such materials are applied in this architecture showing moderate efficiencies around 10 cd/A in all-organic solution processed OLEDs. Overall, the outcome of these studies will actively contribute to the current research on materials for all-solution processed OLEDs.}, 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} } @phdthesis{Kraikivski2005, author = {Kraikivski, Pavel}, title = {Non-equilibrium dynamics of adsorbed polymers and filaments}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-5979}, school = {Universit{\"a}t Potsdam}, year = {2005}, abstract = {In the present work, we discuss two subjects related to the nonequilibrium dynamics of polymers or biological filaments adsorbed to two-dimensional substrates. The first part is dedicated to thermally activated dynamics of polymers on structured substrates in the presence or absence of a driving force. The structured substrate is represented by double-well or periodic potentials. We consider both homogeneous and point driving forces. Point-like driving forces can be realized in single molecule manipulation by atomic force microscopy tips. Uniform driving forces can be generated by hydrodynamic flow or by electric fields for charged polymers. In the second part, we consider collective filament motion in motility assays for motor proteins, where filaments glide over a motor-coated substrate. The model for the simulation of the filament dynamics contains interactive deformable filaments that move under the influence of forces from molecular motors and thermal noise. Motor tails are attached to the substrate and modeled as flexible polymers (entropic springs), motor heads perform a directed walk with a given force-velocity relation. We study the collective filament dynamics and pattern formation as a function of the motor and filament density, the force-velocity characteristics, the detachment rate of motor proteins and the filament interaction. In particular, the formation and statistics of filament patterns such as nematic ordering due to motor activity or clusters due to blocking effects are investigated. Our results are experimentally accessible and possible experimental realizations are discussed.}, subject = {Polymere}, language = {en} } @article{KappelAbelGerhard2011, author = {Kappel, Marcel and Abel, Markus and Gerhard, Reimund}, title = {Characterization and calibration of piezoelectric polymers in situ measurements of body vibrations}, series = {Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques}, volume = {82}, journal = {Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques}, number = {7}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0034-6748}, doi = {10.1063/1.3607435}, pages = {6}, year = {2011}, abstract = {Piezoelectric polymers are known for their flexibility in applications, mainly due to their bending ability, robustness, and variable sensor geometry. It is an optimal material for minimal-invasive investigations in vibrational systems, e.g., for wood, where acoustical impedance matches particularly well. Many applications may be imagined, e. g., monitoring of buildings, vehicles, machinery, alarm systems, such that our investigations may have a large impact on technology. Longitudinal piezoelectricity converts mechanical vibrations normal to the polymer-film plane into an electrical signal, and the respective piezoelectric coefficient needs to be carefully determined in dependence on the relevant material parameters. In order to evaluate efficiency and durability for piezopolymers, we use polyvinylidene fluoride and measure the piezoelectric coefficient with respect to static pressure, amplitude of the dynamically applied force, and long-term stability. A known problem is the slow relaxation of the material towards equilibrium, if the external pressure changes; here, we demonstrate how to counter this problem with careful calibration. Since our focus is on acoustical measurements, we determine accurately the frequency response curve - for acoustics probably the most important characteristic. Eventually, we show that our piezopolymer transducers can be used as a calibrated acoustical sensors for body vibration measurements on a wooden musical instrument, where it is important to perform minimal-invasive measurements. A comparison with the simultaneously recorded airborne sound yields important insight of the mechanism of sound radiation in comparison with the sound propagating in the material. This is especially important for transient signals, where not only the long-living eigenmodes contribute to the sound radiation. Our analyses support that piezopolymer sensors can be employed as a general tool for the determination of the internal dynamics of vibrating systems.}, language = {en} } @phdthesis{Ilic2020, author = {Ilic, Ivan}, title = {Design of sustainable cathodes for Li-ion batteries}, doi = {10.25932/publishup-48368}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-483689}, school = {Universit{\"a}t Potsdam}, pages = {iv, 154}, year = {2020}, abstract = {In recent years people have realised non-renewability of our modern society which relays on spending huge amounts of energy mostly produced from fosil fuels, such as oil and coal, and the shift towards more sustainable energy sources has started. However, sustainable sources of energy, such as wind-, solar- and hydro-energy, produce primarily electrical energy and can not just be poured in canister like many fosil fuels, creating necessity for rechragable batteries. However, modern Li-ion batteries are made from toxic heavy metals and sustainable alternatives are needed. Here we show that naturally abundant catecholic and guaiacyl groups can be utilised to replace heavy metals in Li-ion batteries. Foremost vanillin, a naturally occurring food additive that can be sustainably synthesised from industrial biowaste, lignin, was utilised to synthesise materials that showed extraordinary performance as cathodes in Li-ion batteries. Furthermore, behaviour of catecholic and guiacyl groups in Li-ion system was compared, confirming usability of guiacayl containing biopolymers as cathodes in Li-ion batteries. Lastly, naturally occurring polyphenol, tannic acid, was incorporated in fully bioderived hybrid material that shows performance comparable to commercial Li-ion batteries and good stability. This thesis presents an important advancement in understanding of biowaste derived cathode materials for Li-ion batteries. Further research should be conducted to better understand behaviour of guaiacyl groups during Li-ion battery cycling. Lastly, challenges of incorporation of lignin, an industrial biowaste, have to be addressed and lignin should be incorporated as a cathode material in Li-ion batteries.}, language = {en} } @phdthesis{Gutjahr2007, author = {Gutjahr, Petra}, title = {Conformations of semiflexible polymers and filaments}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-15918}, school = {Universit{\"a}t Potsdam}, year = {2007}, abstract = {The biological function and the technological applications of semiflexible polymers, such as DNA, actin filaments and carbon nanotubes, strongly depend on their rigidity. Semiflexible polymers are characterized by their persistence length, the definition of which is the subject of the first part of this thesis. Attractive interactions, that arise e.g.~in the adsorption, the condensation and the bundling of filaments, can change the conformation of a semiflexible polymer. The conformation depends on the relative magnitude of the material parameters and can be influenced by them in a systematic manner. In particular, the morphologies of semiflexible polymer rings, such as circular nanotubes or DNA, which are adsorbed onto substrates with three types of structures, are studied: (i) A topographical channel, (ii) a chemically modified stripe and (iii) a periodic pattern of topographical steps. The results are compared with the condensation of rings by attractive interactions. Furthermore, the bundling of two individual actin filaments, whose ends are anchored, is analyzed. This system geometry is shown to provide a systematic and quantitative method to extract the magnitude of the attraction between the filaments from experimentally observable conformations of the filaments.}, language = {en} } @phdthesis{Groth2003, author = {Groth, Thomas}, title = {Die Bedeutung der Volumen- und Oberfl{\"a}cheneigenschaften von Biomaterialien f{\"u}r die Adsorption von Proteinen und nachfolgende zellul{\"a}re Reaktionen}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-0001022}, school = {Universit{\"a}t Potsdam}, year = {2003}, abstract = {Es ist schon seit l{\"a}ngerer Zeit bekannt, dass nach Kontakt des Biomaterials mit der biologischen Umgebung bei Implantation oder extrakorporaler Wechselwirkung zun{\"a}chst Proteine aus dem umgebenden Milieu adsorbiert werden, wobei die Oberfl{\"a}cheneigenschaften des Materials die Zusammensetzung der Proteinschicht und die Konformation der darin enthaltenden Proteine determinieren. Die nachfolgende Wechselwirkung von Zellen mit dem Material wird deshalb i.d.R. von der Adsorbatschicht vermittelt. Der Einfluss der Oberfl{\"a}chen auf die Zusammensetzung und Konformation der Proteine und die nachfolgende Wechselwirkung mit Zellen ist von besonderem Interesse, da einerseits eine Aussage {\"u}ber die Anwendbarkeit erm{\"o}glicht wird, andererseits Erkenntnisse {\"u}ber diese Zusammenh{\"a}nge f{\"u}r die Entwicklung neuer Materialien mit verbesserter Biokompatibilit{\"a}t genutzt werden k{\"o}nnen. In der vorliegenden Habilitationsschrift wurde deshalb der Einfluss der Zusammensetzung von Polymeren bzw. von deren Oberfl{\"a}cheneigenschaften auf die Adsorption von Proteinen, den Aktivit{\"a}tszustand der plasmatischen Gerinnung und die Adh{\"a}sion von Zellen untersucht. Dabei wurden auch M{\"o}glichkeiten zur Beeinflussung dieser Vorg{\"a}nge {\"u}ber eine Ver{\"a}nderung der Volumenzusammensetzung oder durch Oberfl{\"a}chenmodifikationen von Biomaterialien vorgestellt. Erkenntnisse aus diesen Arbeiten konnten f{\"u}r die Entwicklung von Membranen f{\"u}r Biohybrid-Organe genutzt werden.}, language = {de} } @article{FandrichBullerWischerhoffetal.2012, author = {Fandrich, Artur and Buller, Jens and Wischerhoff, Erik and Laschewsky, Andr{\´e} and Lisdat, Fred}, title = {Electrochemical detection of the thermally induced phase transition of a thin stimuli-responsive polymer film}, series = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, volume = {13}, journal = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, number = {8}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1439-4235}, doi = {10.1002/cphc.201100924}, pages = {2020 -- 2023}, year = {2012}, language = {en} } @article{CouturierSuetterlinLaschewskyetal.2015, author = {Couturier, Jean-Philippe and S{\"u}tterlin, Martin and Laschewsky, Andr{\´e} and Hettrich, Cornelia and Wischerhoff, Erik}, title = {Responsive Inverse Opal Hydrogels for the Sensing of Macromolecules}, series = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition}, volume = {54}, journal = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition}, number = {22}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1433-7851}, doi = {10.1002/anie.201500674}, pages = {6641 -- 6644}, year = {2015}, abstract = {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.}, language = {en} } @article{Cherstvy2012, author = {Cherstvy, Andrey G.}, title = {Critical polyelectrolyte adsorption under confinement Planar slit, cylindrical pore, and spherical cavity}, series = {Biopolymers}, volume = {97}, journal = {Biopolymers}, number = {5}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0006-3525}, doi = {10.1002/bip.22023}, pages = {311 -- 317}, year = {2012}, abstract = {We explore the properties of adsorption of flexible polyelectrolyte chains in confined spaces between the oppositely charged surfaces in three basic geometries. A method of approximate uniformly valid solutions for the Green function equation for the eigenfunctions of polymer density distributions is developed to rationalize the critical adsorption conditions. The same approach was implemented in our recent study for the inverse problem of polyelectrolyte adsorption onto a planar surface, and on the outer surface of rod-like and spherical obstacles. For the three adsorption geometries investigated, the theory yields simple scaling relations for the minimal surface charge density that triggers the chain adsorption, as a function of the Debye screening length and surface curvature. The encapsulation of polyelectrolytes is governed by interplay of the electrostatic attraction energy toward the adsorbing surface and entropic repulsion of the chain squeezed into a thin slit or small cavities. Under the conditions of surface-mediated confinement, substantially larger polymer linear charge densities are required to adsorb a polyelectrolyte inside a charged spherical cavity, relative to a cylindrical pore and to a planar slit (at the same interfacial surface charge density). Possible biological implications are discussed briefly in the end.}, language = {en} } @article{BlavatskaMetzler2015, author = {Blavatska, Viktoria and Metzler, Ralf}, title = {Conformational properties of complex polymers: rosette versus star-like structures}, series = {Journal of physics : A, Mathematical and theoretical}, volume = {48}, journal = {Journal of physics : A, Mathematical and theoretical}, number = {13}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1751-8113}, doi = {10.1088/1751-8113/48/13/135001}, pages = {14}, year = {2015}, abstract = {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.}, language = {en} } @phdthesis{Behrendt2018, author = {Behrendt, Felix Nicolas}, title = {New bio-based polymers}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-418316}, school = {Universit{\"a}t Potsdam}, pages = {vii, 153}, year = {2018}, abstract = {Redox-responsive polymers, such as poly(disulfide)s, are a versatile class of polymers with potential applications including gene- and drug-carrier systems. Their degradability under reductive conditions allows for a controlled response to the different redox states that are present throughout the body. Poly(disulfide)s are typically synthesized by step growth polymerizations. Step growth polymerizations, however, may suffer from low conversions and therefore low molar masses, limiting potential applications. The purpose of this thesis was therefore to find and investigate new synthetic routes towards the synthesis of amino acid-based poly(disulfide)s. The different routes in this thesis include entropy-driven ring opening polymerizations of novel macrocyclic monomers, derived from cystine derivatives. These monomers were obtained with overall yields of up to 77\% and were analyzed by mass spectrometry as well as by 1D and 2D NMR spectroscopy. The kinetics of the entropy-driven ring-opening metathesis polymerization (ED-ROMP) were thoroughly investigated in dependence of temperature, monomer concentration, and catalyst concentration. The polymerization was optimized to yield poly(disulfide)s with weight average molar masses of up to 80 kDa and conversions of ~80\%, at the thermodynamic equilibrium. Additionally, an alternative metal free polymerization, namely the entropy-driven ring-opening disulfide metathesis polymerization (ED-RODiMP) was established for the polymerization of the macrocyclic monomers. The effect of different solvents, concentrations and catalyst loadings on the polymerization process and its kinetics were studied. Polymers with very high weight average molar masses of up to 177 kDa were obtained. Moreover, various post-polymerization reactions were successfully performed. This work provides the first example of the homopolymerization of endo-cyclic disulfides by ED-ROMP and the first substantial study into the kinetics of the ED-RODiMP process.}, language = {en} }