TY - JOUR A1 - Geiger, Christina A1 - Reitenbach, Julija A1 - Henschel, Cristiane A1 - Kreuzer, Lucas A1 - Widmann, Tobias A1 - Wang, Peixi A1 - Mangiapia, Gaetano A1 - Moulin, Jean-François A1 - Papadakis, Christine M. A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter T1 - Ternary nanoswitches realized with multiresponsive PMMA-b-PNIPMAM films in mixed water/acetone vapor atmospheres JF - Advanced engineering materials N2 - To systematically add functionality to nanoscale polymer switches, an understanding of their responsive behavior is crucial. Herein, solvent vapor stimuli are applied to thin films of a diblock copolymer consisting of a short poly(methyl methacrylate) (PMMA) block and a long poly(N-isopropylmethacrylamide) (PNIPMAM) block for realizing ternary nanoswitches. Three significantly distinct film states are successfully implemented by the combination of amphiphilicity and co-nonsolvency effect. The exposure of the thin films to nitrogen, pure water vapor, and mixed water/acetone (90 vol%/10 vol%) vapor switches the films from a dried to a hydrated (solvated and swollen) and a water/acetone-exchanged (solvated and contracted) equilibrium state. These three states have distinctly different film thicknesses and solvent contents, which act as switch positions "off," "on," and "standby." For understanding the switching process, time-of-flight neutron reflectometry (ToF-NR) and spectral reflectance (SR) studies of the swelling and dehydration process are complemented by information on the local solvation of functional groups probed with Fourier-transform infrared (FTIR) spectroscopy. An accelerated responsive behavior beyond a minimum hydration/solvation level is attributed to the fast build-up and depletion of the hydration shell of PNIPMAM, caused by its hydrophobic moieties promoting a cooperative hydration character. KW - co-nonsolvency KW - diblock copolymers KW - nanoswitches KW - neutron reflectometry KW - thin films Y1 - 2021 U6 - https://doi.org/10.1002/adem.202100191 SN - 1438-1656 SN - 1527-2648 VL - 23 IS - 11 PB - Wiley-VCH CY - Weinheim ER - TY - THES A1 - Arvind, Malavika T1 - Regarding the role of aggregation and structural order on the mechanism of molecular doping of semiconducting polymers T1 - Die Rolle von Aggregation und struktureller Ordnung auf den Mechanismus der molekularen Dotierung von halbleitenden Polymeren BT - from solutions to films BT - von Lösungen zu Filmen N2 - Polymeric semiconductors are strong contenders for replacing traditional inorganic semiconductors in electronic applications requiring low power, low cost and flexibility, such as biosensors, flexible solar cells and electronic displays. Molecular doping has the potential to enable this revolution by improving the conductivity and charge transport properties of this class of materials. Despite decades of research in this field, gaps in our understanding of the nature of dopant–polymer interactions has resulted in limited commercialization of this technology. This work aims at providing a deeper insight into the underlying mechanisms of molecular p-doping of semiconducting polymers in the solution and solid-state, and thereby bring the scientific community closer to realizing the dream of making organic semiconductors commonplace in the electronics industry. The role of 1) dopant size/shape, 2) polymer chain aggregation and 3) charge delocalization on the doping mechanism and efficiency is addressed using optical (UV-Vis-NIR) and electron paramagnetic resonance (EPR) spectroscopies. By conducting a comprehensive study of the nature and concentration of the doping-induced species in solutions of the polymer poly(3-hexylthiophene) (P3HT) with 3 different dopants, we identify the unique optical signatures of the delocalized polaron, localized polaron and charge-transfer complex, and report their extinction coefficient values. Furthermore, with X-ray diffraction, atomic force microscopy and electrical conductivity measurements, we study the impact of processing technique and doping mechanism on the morphology and thereby, charge transport through the doped films. This work demonstrates that the doping mechanism and type of doping-induced species formed are strongly influenced by the polymer backbone arrangement rather than dopant shape/size. The ability of the polymer chain to aggregate is found to be crucial for efficient charge transfer (ionization) and polaron delocalization. At the same time, our results suggest that the high ionization efficiency of a dopant–polymer system in solution may subsequently hinder efficient charge transport in the solid-state due to the reduction in the fraction of tie chains, which enable charges to move efficiently between aggregated domains in the films. This study demonstrates the complex multifaceted nature of polymer doping while providing important hints for the future design of dopant-host systems and film fabrication techniques. N2 - Polymer-Halbleiter sind vielversprechende Kandidaten für den Ersatz traditioneller anorganischer Halbleiter in elektronischen Anwendungen, die einen geringen Stromverbrauch, niedrige Kosten und mechanische Flexibilität erfordern, wie z.B. Biosensoren, flexible Solarzellen und elektronische Bildschirme. Molekulare Dotierung hat das Potenzial, diese Revolution zu ermöglichen, indem sie die Leitfähigkeit und die Ladungstransporteigenschaften dieser Materialklasse verbessert. Trotz jahrzehntelanger Forschung auf diesem Gebiet hat das unvollständige Verständnis der Dotierstoff-Polymer-Wechselwirkungen nur zu einer begrenzten Kommerzialisierung dieser Technologie geführt.Ziel dieser Arbeit ist es, einen tieferen Einblick in die zugrunde liegenden Mechanismen der molekularen p-Dotierung von halbleitenden Polymeren in Lösung und im festen Zustand zu geben und dadurch die wissenschaftliche Gemeinschaft näher an die Verwirklichung des Traums heran zu bringen, organische Halbleiter in der Elektronikindustrie alltäglich zu machen. Diese Arbeit zeigt, dass der Dotierungsmechanismus und die Art der gebildeten, dotierungsinduzierten Spezies eher durch die Anordnung des Polymerrückgrats als durch die Form/Größe des Dotierstoffs beeinflusst werden. Die Fähigkeit der Polymerkette, zu aggregieren, stellt sich als entscheidend für einen effizienten Ladungstransfer (d.h. Ionisierung) und die Polaron-Delokalisierung heraus. Gleichzeitig deuten unsere Ergebnisse darauf hin, dass die hohe Ionisationseffizienz eines Dotierstoff-Polymersystems in der Lösung eine Beinträchtigung des effizienten Ladungstransport im festen Zustand nach sich ziehen kann, da der Anteil der Verbindungsketten, die eine effiziente Bewegung von Ladungen zwischen aggregierten Domänen in dünnen Filmen ermöglichen, reduziert wird. Diese Arbeit verdeutlicht die komplexe, vielschichtige Natur der Polymerdotierung und gibt dabei wichtige Hinweise für das zukünftige Design von Dotierstoff-Wirtssystemen und Filmherstellungstechniken. KW - molecular doping KW - organic semiconductors KW - Lewis acid doping KW - optical spectroscopy KW - thin films KW - semiconducting polymer KW - conductivity KW - dip doping KW - polymer aggregation KW - Dotierung KW - Polymer-Halbleiter KW - Leitfähigkeit KW - Lewis-Säure Dotierung KW - organische Halbleiter KW - Polymeraggregation KW - halbleitendes Polymer KW - Dünn film KW - optische Spektroskopie KW - molekulare Dotierung KW - Dip-Dotierung Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-500606 ER -