Highlight Publications 2018

Fast Access to Amphiphilic Multiblock Architectures by the Anionic Copolymerization of Aziridines and Ethylene Oxide
Tassilo Gleede, Elisabeth Rieger, Jan Blankenburg, Katja Klein, and Frederik R. Wurm
Fast Access to Amphiphilic Multiblock Architectures by the Anionic Copolymerization of Aziridines and Ethylene Oxide
An ideal system for stimuli-responsive and amphiphilic (block) polymers would be the copolymerization of aziridines with epoxides. However, to date, no copolymerization of these two highly strained three-membered heterocycles had been achieved. We report the combination of living oxy- and azaanionic ring-opening polymerization of ethylene oxide (EO) and sulfonamide-activated aziridines. In a single step, well-defined amphiphilic block copolymers are obtained by a one-pot copolymerization. The highest difference of reactivity ratios ever reported for an anionic copolymerization (with r1=265 and r2=0.004 for 2-methyl-N-tosylaziridine/ EO) led to the formation of block copolymers in a closed system. The amphiphilic diblock copolymers were used a novel class of nonionic and responsive surfactants. In addition, this unique comonomer reactivity allowed fast access to multiblock copolymers: we prepared the first amphiphilic penta- or tetrablock copolymers containing aziridines in only one or two steps, respectively. These examples render the combination of epoxide and aziridine copolymerization to a powerful strategy to sophisticated macromolecular architectures and nanostructures.
© MPI-P (2018)
Block copolymers of aziridines and ethylene oxide are prepared in a closed-reactor without sequential monomer addition.
Plastics of the future? The impact of biodegradable polymers on the environment and on society
Tobias Haider, Carolin Völker, Johanna Kramm, Katharina Landfester, Frederik R. Wurm
Plastics of the future? The impact of biodegradable polymers on the environment and on society
We are living in a plastic age. For most of us, life without polymers and plastics is unthinkable. However, in recent years the littering of plastics and the problems related to their persistence in the environment have become a major focus in research and the news. Biodegradable polymers might be a suitable alternative to commodity plastics to minimize the impact of plastics on the environment. However, their degradation rates crucially depend on the environments they end up in, such as soil or marine water, or when used in biomedical devices. We show that biodegradation tests carried out in artificial environments lack transferability to real conditions and, therefore, highlight the necessity of environmentally authentic and relevant field‐testing conditions. In addition, we focus on ecotoxicological implications of biodegradable polymers. We also consider the social aspects and ask how biodegradable polymers influence consumer behavior and municipal waste management. Taken together, this study is intended as a contribution towards evaluating the potential of biodegradable polymers as alternative materials to commodity plastics.
© Wiley VCH (2018)
Biodegradable polymers. Currents materials and future perspectives are discussed.
Evidence for auto-catalytic mineral dissolution from surface-specific vibrational spectroscopy
Jan Schaefer, Ellen H. G. Backus & Mischa Bonn
Evidence for auto-catalytic mineral dissolution from surface-specific vibrational spectroscopy
In nature, many geologically relevant processes are driven by non-equilibrium interfacial effects: Water typically flows and doesn’t stand still. A key example is the dissolution of minerals, like silica, in water. By using time-dependent surface specific spectroscopy in the presence and absence of flow of water, we determine the dissolution kinetics of silica in a direct way. The interfacial insights of this approach reveal that the macroscopic dissolution process of silica is limited by diffusion. The molecular dissolution mechanism appears autocatalytic: the presence of dissolved silicate close to the interface speeds up the dissolution process.
© Nature (2018)
Interfacial spectroscopy reveals: Silica dissolution is self-accelerating and limited by diffusion.
Vibrational coupling between organic and inorganic sub‐lattices of hybrid perovskites
Maksim Grechko Simon A. Bretschneider Laura Vietze Heejae Kim Mischa Bonn
Vibrational coupling between organic and inorganic sub‐lattices of hybrid perovskites
The excellent photovoltaic performance of perovskite solar cells has inspired significant interest in the fundamental photophysical properties of this promising material. One of the most challenging fundamental issues is coupling between different motions of electrons and nuclei in the lattice of perovskite semiconductors. In the present work, we reveal direct coupling between phonon vibrations of inorganic sub-lattice and high-frequency molecular vibrations of organic sub-lattice of hybrid organic-inorganic perovskites. Mixing of the phonon and molecular vibrations can provide additional energy relaxation pathways for photoexcited electrons in the conduction band and, thus, elucidate the faster hot-carrier cooling rates in the MA/FAPbI3 as compared to the CsPbI3 perovskites.
© Wiley VCH (2018)
A newly developed spectroscopy reveals coupling between low-frequency phonon modes and high-frequency molecular vibrations in a hybrid organic – inorganic perovskite.
Red-Light-Controlled Release of Drug–Ru Complex Conjugates from Metallopolymer Micelles for Phototherapy in Hypoxic Tumor Environments
Wen Sun, Yan Wen, Raweewan Thiramanas, Mingjia Chen, Jianxiong Han, Ningqiang Gong, Manfred Wagner, Shuai Jiang, Michael S. Meijer, Sylvestre Bonnet, Hans-Jürgen Butt, Volker Mailänder, Xing-Jie Liang, and Si Wu
Red-Light-Controlled Release of Drug–Ru Complex Conjugates from Metallopolymer Micelles for Phototherapy in Hypoxic Tumor Environments
Amphiphilic metallopolymers, which contain photocleavable drug-Ru complex conjugates, self-assemble into micelles. The micelles are biocompatible and carry the conjugates into tumor cells. Subsequent red light irradiation induces intracellular release of the drug-Ru complex conjugates. Because the photoinduced release is oxygen-independent, the novel metallopolymer provides a new platform for phototherapy against hypoxic tumors in vivo.
© Wiley (2018)
Layered Thiadiazoloquinoxaline Containing Long Pyrene‐fused N‐Heteroacenes
Ben-Lin Hu, Ke Zhang, Cunbin An, Dieter Schollmeyer, Wojciech Pisula, and Martin Baumgarten
Layered Thiadiazoloquinoxaline Containing Long Pyrene‐fused N‐Heteroacenes
Three thiadiazoloquinoxaline containing long pyrene-fused N-heteroacenes with 8, 13 and 18 rings were designed and synthesized, which show high electron affinities (EAs) of ~4.1 eV derived from the onset of reductive peaks in cyclic voltammetry. Crystal structure analysis demonstrated in-plane extension through close contacts of thiadiazoles and layered packing enabling in-plane and interlayer electron transport. Organic field-effect transistor devices provided electron mobilities, which supplies a potential way to enhance the charge transport in long N-heteroacenes.
© Wiley VCH (2018)
Efficient Hot Electron Transfer in Quantum Dot-Sensitized Mesoporous Oxides at Room Temperature
Hai I. Wang, Ivan Infante, Stephanie ten Brinck, Enrique Cánovas, and Mischa Bonn
Efficient Hot Electron Transfer in Quantum Dot-Sensitized Mesoporous Oxides at Room Temperature
The efficiency of a single bandgap solar cell, such as silicon, is limited to ~31%. This limit is primarily the result of very rapid relaxation of electrons, once they are generated by a photon. For photons that have energies exceeding the bandgap energy, this excess energy is lost in this relaxation process. In order to circumvent such losses, and increase solar cell efficiency, the extraction of hot carriers towards selective contacts is required to be faster than thermalization in the absorber. Quantum dot (QD)-sensitized oxides have long been proposed as an appealing system to harvest hot carriers for solar energy conversion. Previous work has demonstrated the possibility of hot electron extraction in quantum dot (QD)-sensitized systems, but only at low temperatures (e.g. 77 Kelvin). Here, we demonstrate a room-temperature hot electron transfer with unity quantum efficiency in strongly coupled PbS quantum dot-sensitized mesoporous oxide. Such achievement is realized by enhancing the electronic coupling between QDs and oxides, which ensures an ultrafast hot electron transfer process (sub-100 fs) that can effectively compete with the hot carrier thermalization processes. These results provide new insights into circumventing thermal losses in sensitized systems, with potential relevance for low-cost solar energy conversion schemes.
© ACS (2018)
Room-temperature hot electron transfer with unity quantum efficiency in strongly coupled PbS quantum dot-sensitized mesoporous oxide
 
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