@misc{BreternitzLehmannBarnettetal.2019, author = {Breternitz, Joachim and Lehmann, Frederike and Barnett, Sarah A. and Nowell, Harriott and Schorr, Susan}, title = {Zur Rolle der Iodid-Methylammonium-Interaktion in der Ferroelektrizit{\"a}t in CH3NH3PbI3}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1}, issn = {1866-8372}, doi = {10.1002/ange.201910599}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-525674}, pages = {7}, year = {2019}, abstract = {Ihre außergew{\"o}hnlich hohen Konversionseffizienzen von {\"u}ber 20 \% und die einfache Zellherstellung machen Hybridperowskite zu heißen Kandidaten f{\"u}r alternative Solarzellenmaterialien. CH3NH3PbI3 als Archetyp dieser Materialklasse besitzt außergew{\"o}hnliche Eigenschaften wie eine sehr effiziente Umwandlung von Solarenergie, wobei besonders Ferroelektrizit{\"a}t als m{\"o}gliche Erkl{\"a}rung in den Fokus ger{\"u}ckt ist. Diese erfordert allerdings eine nicht-zentrosymmetrische Kristallstruktur als notwendige Voraussetzung. Wir stellen hier eine Erkl{\"a}rung des Symmetriebruchs in diesem Material auf kristallographischem, d. h. fernordnungs-basiertem, Wege vor. W{\"a}hrend das Molek{\"u}lkation CH3NH3+ intrinsisch polar ist, ist es extrem fehlgeordnet und kann deshalb nicht die einzige Erkl{\"a}rung darstellen. Es verzerrt allerdings das umgebende Kristallgitter und ruft dadurch eine Verschiebung der Iod-Atome von den zentrosymmetrischen Positionen hervor.}, language = {de} } @misc{BreternitzLehmannBarnettetal.2019, author = {Breternitz, Joachim and Lehmann, Frederike and Barnett, Sarah A. and Nowell, Harriott and Schorr, Susan}, title = {Role of the Iodide-methylammonium interaction in the ferroelectricity of CH3NH3PbI3}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1}, issn = {1866-8372}, doi = {10.25932/publishup-51822}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-518227}, pages = {7}, year = {2019}, abstract = {Excellent conversion efficiencies of over 20\% and facile cell production have placed hybrid perovskites at the forefront of novel solar cell materials, with CH3NH3PbI3 being an archetypal compound. The question why CH3NH3PbI3 has such extraordinary characteristics, particularly a very efficient power conversion from absorbed light to electrical power, is hotly debated, with ferroelectricity being a promising candidate. This does, however, require the crystal structure to be non-centrosymmetric and we herein present crystallographic evidence as to how the symmetry breaking occurs on a crystallographic and, therefore, long-range level. Although the molecular cation CH3NH3+ is intrinsically polar, it is heavily disordered and this cannot be the sole reason for the ferroelectricity. We show that it, nonetheless, plays an important role, as it distorts the neighboring iodide positions from their centrosymmetric positions.}, language = {en} } @phdthesis{Dambowsky2021, author = {Dambowsky, Ina}, title = {Bioinspirierte Komposite - Strukturbildung durch Verkleben von Nano- oder Mesokristallen mit funktionalisierten Poly(2-oxazolin)en}, doi = {10.25932/publishup-52367}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-523671}, school = {Universit{\"a}t Potsdam}, pages = {XII, 220}, year = {2021}, abstract = {Die herausragenden mechanischen Eigenschaften nat{\"u}rlicher anorganisch-organischer Kompositmaterialien wie Knochen oder Muschelschalen entspringen ihrer hierarchischen Struktur, die von der nano- bis hinauf zur makroskopischen Ebene reicht, und einer kontrollierten Verbindung entlang der Grenzfl{\"a}chen der anorganischen und organischen Komponenten. Ausgehend von diesen Schl{\"u}sselprinzipien des biologischen Materialdesigns wurden in dieser Arbeit zwei Konzepte f{\"u}r die bioinspirierte Strukturbildung von Kompositen untersucht, die auf dem Verkleben von Nano- oder Mesokristallen mit funktionalisierten Poly(2-oxazolin)-Blockcopolymeren beruhen sowie deren Potenzial zur Herstellung bioinspirierter selbstorganisierter hierarchischer anorganisch-organischer Verbundstrukturen ohne {\"a}ußere Kr{\"a}fte beleuchtet. Die Konzepte unterschieden sich in den verwendeten anorganischen Partikeln und in der Art der Strukturbildung. {\"U}ber einen modularen Ansatz aus Polymersynthese und polymeranaloger Thiol-En-Funktionalisierung wurde erfolgreich eine Bibliothek von Poly(2-oxazolin)en mit unterschiedlichen Funktionalit{\"a}ten erstellt. Die Blockcopolymere bestehen aus einem kurzen partikelaffinen "Klebeblock", der aus Thiol-En-funktionalisiertem Poly(2-(3-butenyl)-2-oxazolin) besteht, und einem langen wasserl{\"o}slichen, strukturbildenden Block, der aus thermoresponsivem und kristallisierbarem Poly(2-isopropyl-2-oxazolin) besteht und hierarchische Morphologien ausbildet. Verschiedene analytische Untersuchungen wie Turbidimetrie, DLS, DSC, SEM oder XRD machten das thermoresponsive bzw. das Kristallisationsverhalten der Blockcopolymere in Abh{\"a}ngigkeit vom eingef{\"u}hrten Klebeblock zug{\"a}nglich. Es zeigte sich, dass diese Polymere ein komplexes temperatur- und pH-abh{\"a}ngiges Tr{\"u}bungsverhalten aufweisen. Hinsichtlich der Kristallisation {\"a}nderte der Klebeblock nicht die nanoskopische Kristallstruktur; er beeinflusste jedoch die Kristallisationszeit, den Kristallisationsgrad und die hierarchische Morphologie. Dieses Ergebnis wurde auf das unterschiedliche Aggregationsverhalten der Polymere in Wasser zur{\"u}ckgef{\"u}hrt. F{\"u}r die Herstellung von Kompositen nutzte Konzept 1 mikrometergroße Kupferoxalat-Mesokristalle, die eine innere Nanostruktur aufweisen. Die Strukturbildung {\"u}ber den anorganischen Teil wurde durch das Verkleben und Anordnen dieser Partikel erstrebt. Konzept 1 erm{\"o}glichte homogene freistehende stabile Kompositfilme mit einem hohen anorganischen Anteil. Die Partikel-Polymer-Kombination vereinte jedoch ung{\"u}nstige Eigenschaften in sich, d. h. ihre L{\"a}ngenskalen waren zu unterschiedlich, was die Selbstassemblierung der Partikel verhinderte. Aufgrund des geringen Aspektverh{\"a}ltnisses von Kupferoxalat blieb auch die gegenseitige Ausrichtung durch {\"a}ußere Kr{\"a}fte erfolglos. Im Ergebnis eignet sich das Kupferoxalat-Poly(2-oxazolin)-Modellsystem nicht f{\"u}r die Herstellung hierarchischer Kompositstrukturen. Im Gegensatz dazu verwendet Konzept 2 scheibenf{\"o}rmige Laponit®-Nanopartikel und kristallisierbare Blockcopolymere zur Strukturbildung {\"u}ber die organische Komponente durch polymervermittelte Selbstassemblierung. Komplement{\"a}re Analysemethoden (Zeta-Potenzial, DLS, SEM, XRD, DSC, TEM) zeigten sowohl eine kontrollierte Wechselwirkung zwischen den Komponenten in w{\"a}ssriger Umgebung als auch eine kontrollierte Strukturbildung, die in selbstassemblierten Nanokompositen resultiert, deren Struktur sich {\"u}ber mehrere L{\"a}ngenskalen erstreckt. Es wurde gezeigt, dass die negativ geladenen Klebebl{\"o}cke spezifisch und selektiv an den positiv geladenen R{\"a}ndern der Laponit®-Partikel binden und so Polymer-Laponit®-Nanohybridpartikel entstehen, die als Grundbausteine f{\"u}r die Kompositbildung dienen. Die Hybridpartikel sind bei Raumtemperatur elektrosterisch stabilisiert - sterisch durch ihre langen, mit Wasser wechselwirkenden Poly(2-isopropyl-2-oxazolin)-Bl{\"o}cke und elektrostatisch {\"u}ber die negativ geladenen Laponit®-Fl{\"a}chen. Im Ergebnis ließ sich Konzept 2 und damit die Strukturbildung {\"u}ber die organische Komponente erfolgreich umsetzten. Das Laponit®-Poly(2-oxazolin)-Modellsystem er{\"o}ffnete den Weg zu selbstassemblierten geschichteten quasi-hierarchischen Nanokompositstrukturen mit hohem anorganischen Anteil. Abh{\"a}ngig von der frei verf{\"u}gbaren Polymerkonzentration bei der Kompositbildung entstanden zwei unterschiedliche Komposit-Typen. Dar{\"u}ber hinaus entwarf die Arbeit einen Erkl{\"a}rungsansatz f{\"u}r den polymervermittelten Bildungsprozess der Komposit-Strukturen. Insgesamt legt diese Arbeit Struktur-Prozess-Eigenschafts-Beziehungen offen, um selbstassemblierte bioinspirierte Kompositstrukturen zu bilden und liefert neue Einsichten zu einer geeigneten Kombination an Komponenten und Herstellungsbedingungen, die eine kontrollierte selbstassemblierte Strukturbildung mithilfe funktionalisierter Poly(2-oxazolin)-Blockcopolymere erlauben.}, language = {de} } @misc{PerovicQinOschatz2020, author = {Perovic, Milena and Qin, Qing and Oschatz, Martin}, title = {From molecular precursors to nanoparticles}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, issn = {1866-8372}, doi = {10.25932/publishup-51614}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-516140}, pages = {23}, year = {2020}, abstract = {Nanoporous carbon materials (NCMs) provide the "function" of high specific surface area and thus have large interface area for interactions with surrounding species, which is of particular importance in applications related to adsorption processes. The strength and mechanism of adsorption depend on the pore architecture of the NCMs. In addition, chemical functionalization can be used to induce changes of electron density and/or electron density distribution in the pore walls, thus further modifying the interactions between carbons and guest species. Typical approaches for functionalization of nanoporous materials with regular atomic construction like porous silica, metal-organic frameworks, or zeolites, cannot be applied to NCMs due to their less defined local atomic construction and abundant defects. Therefore, synthetic strategies that offer a higher degree of control over the process of functionalization are needed. Synthetic approaches for covalent functionalization of NCMs, that is, for the incorporation of heteroatoms into the carbon backbone, are critically reviewed with a special focus on strategies following the concept "from molecules to materials." Approaches for coordinative functionalization with metallic species, and the functionalization by nanocomposite formation between pristine carbon materials and heteroatom-containing carbons, are introduced as well. Particular focus is given to the influences of these functionalizations in adsorption-related applications.}, language = {en} } @misc{SchoenemannKocAldredetal.2019, author = {Sch{\"o}nemann, Eric and Koc, Julian and Aldred, Nick and Clare, Anthony S. and Laschewsky, Andr{\´e} and Rosenhahn, Axel and Wischerhoff, Erik}, title = {Synthesis of novel sulfobetaine polymers with differing dipole orientations in their side chains, and their effects on the antifouling properties}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1}, issn = {1866-8372}, doi = {10.25932/publishup-52482}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-524820}, pages = {9}, year = {2019}, abstract = {The impact of the orientation of zwitterionic groups, with respect to the polymer backbone, on the antifouling performance of thin hydrogel films made of polyzwitterions is explored. In an extension of the recent discussion about differences in the behavior of polymeric phosphatidylcholines and choline phosphates, a quasi-isomeric set of three poly(sulfobetaine methacrylate)s is designed for this purpose. The design is based on the established monomer 3-[N-2-(methacryloyloxy)ethyl-N,N-dimethyl]ammonio-propane-1-sulfonate and two novel sulfobetaine methacrylates, in which the positions of the cationic and the ionic groups relative to the polymerizable group, and thus also to the polymer backbone, are altered. The effect of the varied segmental dipole orientation on their water solubility, wetting behavior by water, and fouling resistance is compared. As model systems, the adsorption of the model proteins bovine serum albumin (BSA), fibrinogen, and lysozyme onto films of the various polyzwitterion surfaces is studied, as well as the settlement of a diatom (Navicula perminuta) and barnacle cyprids (Balanus improvisus) as representatives of typical marine fouling communities. The results demonstrate the important role of the zwitterionic group's orientation on the polymer behavior and fouling resistance}, language = {en} } @misc{WalkowiakLuGradzielskietal.2020, author = {Walkowiak, Jacek and Lu, Yan and Gradzielski, Michael and Zauscher, Stefan and Ballauff, Matthias}, title = {Thermodynamic analysis of the uptake of a protein in a spherical polyelectrolyte brush}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1}, issn = {1866-8372}, doi = {10.25932/publishup-51730}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-517307}, pages = {10}, year = {2020}, abstract = {A thermodynamic study of the adsorption of Human Serum Albumin (HSA) onto spherical polyelectrolyte brushes (SPBs) by isothermal titration calorimetry (ITC) is presented. The SPBs are composed of a solid polystyrene core bearing long chains of poly(acrylic acid). ITC measurements done at different temperatures and ionic strengths lead to a full set of thermodynamicbinding constants together with the enthalpies and entropies of binding. The adsorption of HSA onto SPBs is described with a two-step model. The free energy of binding Delta Gb depends only weakly on temperature because of a marked compensation of enthalpy by entropy. Studies of the adsorbed HSA by Fourier transform infrared spectroscopy (FT-IR) demonstrate no significant disturbance in the secondary structure of the protein. The quantitative analysis demonstrates that counterion release is the major driving force for adsorption in a process where proteins become multivalent counterions of the polyelectrolyte chains upon adsorption. A comparison with the analysis of other sets of data related to the binding of HSA to polyelectrolytes demonstrates that the cancellation of enthalpy and entropy is a general phenomenon that always accompanies the binding of proteins to polyelectrolytes dominated by counterion release.}, language = {en} } @misc{NicolaiWeishauptBaesleretal.2021, author = {Nicolai, Merle Marie and Weishaupt, Ann-Kathrin and Baesler, Jessica and Brinkmann, Vanessa and Wellenberg, Anna and Winkelbeiner, Nicola Lisa and Gremme, Anna and Aschner, Michael and Fritz, Gerhard and Schwerdtle, Tanja and Bornhorst, Julia}, title = {Effects of manganese on genomic integrity in the multicellular model organism Caenorhabditis elegans}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1173}, issn = {1866-8372}, doi = {10.25932/publishup-52327}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-523275}, pages = {18}, year = {2021}, abstract = {Although manganese (Mn) is an essential trace element, overexposure is associated with Mn-induced toxicity and neurological dysfunction. Even though Mn-induced oxidative stress is discussed extensively, neither the underlying mechanisms of the potential consequences of Mn-induced oxidative stress on DNA damage and DNA repair, nor the possibly resulting toxicity are characterized yet. In this study, we use the model organism Caenorhabditis elegans to investigate the mode of action of Mn toxicity, focusing on genomic integrity by means of DNA damage and DNA damage response. Experiments were conducted to analyze Mn bioavailability, lethality, and induction of DNA damage. Different deletion mutant strains were then used to investigate the role of base excision repair (BER) and dePARylation (DNA damage response) proteins in Mn-induced toxicity. The results indicate a dose- and time-dependent uptake of Mn, resulting in increased lethality. Excessive exposure to Mn decreases genomic integrity and activates BER. Altogether, this study characterizes the consequences of Mn exposure on genomic integrity and therefore broadens the molecular understanding of pathways underlying Mn-induced toxicity. Additionally, studying the basal poly(ADP-ribosylation) (PARylation) of worms lacking poly(ADP-ribose) glycohydrolase (PARG) parg-1 or parg-2 (two orthologue of PARG), indicates that parg-1 accounts for most of the glycohydrolase activity in worms.}, language = {en} } @misc{KopyraWierzbickaTulwinetal.2021, author = {Kopyra, Janina and Wierzbicka, Paulina and Tulwin, Adrian and Thiam, Guillaume and Bald, Ilko and Rabilloud, Franck and Abdoul-Carime, Hassan}, title = {Experimental and theoretical studies of dissociative electron attachment to metabolites oxaloacetic and citric acids}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1156}, issn = {1866-8372}, doi = {10.25932/publishup-52182}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-521829}, pages = {16}, year = {2021}, abstract = {In this contribution the dissociative electron attachment to metabolites found in aerobic organisms, namely oxaloacetic and citric acids, was studied both experimentally by means of a crossed-beam setup and theoretically through density functional theory calculations. Prominent negative ion resonances from both compounds are observed peaking below 0.5 eV resulting in intense formation of fragment anions associated with a decomposition of the carboxyl groups. In addition, resonances at higher energies (3-9 eV) are observed exclusively from the decomposition of the oxaloacetic acid. These fragments are generated with considerably smaller intensities. The striking findings of our calculations indicate the different mechanism by which the near 0 eV electron is trapped by the precursor molecule to form the transitory negative ion prior to dissociation. For the oxaloacetic acid, the transitory anion arises from the capture of the electron directly into some valence states, while, for the citric acid, dipole- or multipole-bound states mediate the transition into the valence states. What is also of high importance is that both compounds while undergoing DEA reactions generate highly reactive neutral species that can lead to severe cell damage in a biological environment.}, language = {en} } @misc{BlockGuenterDuarteRodriguesetal.2021, author = {Block, Inga and G{\"u}nter, Christina and Duarte Rodrigues, Alysson and Paasch, Silvia and Hesemann, Peter and Taubert, Andreas}, title = {Carbon Adsorbents from Spent Coffee for Removal of Methylene Blue and Methyl Orange from Water}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {14}, issn = {1866-8372}, doi = {10.25932/publishup-52165}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-521653}, pages = {20}, year = {2021}, abstract = {Activated carbons (ACs) were prepared from dried spent coffee (SCD), a biological waste product, to produce adsorbents for methylene blue (MB) and methyl orange (MO) from aqueous solution. Pre-pyrolysis activation of SCD was achieved via treatment of the SCD with aqueous sodium hydroxide solutions at 90 °C. Pyrolysis of the pretreated SCD at 500 °C for 1 h produced powders with typical characteristics of AC suitable and effective for dye adsorption. As an alternative to the rather harsh base treatment, calcium carbonate powder, a very common and abundant resource, was also studied as an activator. Mixtures of SCD and CaCO3 (1:1 w/w) yielded effective ACs for MO and MB removal upon pyrolysis needing only small amounts of AC to clear the solutions. A selectivity of the adsorption process toward anionic (MO) or cationic (MB) dyes was not observed.}, language = {en} } @phdthesis{Sanay2021, author = {Sanay, Berran}, title = {Monomers and polymers based on renewable resources for new photopolymer coating}, doi = {10.25932/publishup-51868}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-518684}, school = {Universit{\"a}t Potsdam}, pages = {XXXIII, 124}, year = {2021}, abstract = {The present work focuses on minimising the usage of toxic chemicals by integration of the biobased monomers, derived from fatty acid esters, to photopolymerization processes, which are known to be nature friendly. Internal double bond present in the oleic acid was converted to more reactive (meth)acrylate or epoxy group. Biobased starting materials, functionalized by different pendant groups, were used for photopolymerizing formulations to design of new polymeric structures by using ultraviolet light emitting diode (UV-LED) (395 nm) via free radical polymerization or cationic polymerization. New (meth)acrylates (2,3 and 4) consisting of two isomers, methyl 9-((meth)acryloyloxy)-10-hydroxyoctadecanoate / methyl 9-hydroxy-10-((meth)acryloyloxy)octadecanoate (2 and 3) and methyl 9-(1H-imidazol-1-yl)-10-(methacryloyloxy)octadecanoate / methyl 9-(methacryloyloxy)-10-(1H-imidazol-1-yl)octadecanoate (4), modified from oleic acid mix, and ionic liquid monomers (1a and 1b) bearing long alkyl chain were polymerized photochemically. New (meth)acrylates are based on vegetable oil, and ionic liquids (ILs) have nonvolatile behaviour. Therefore, both monomer types have green approach. Photoinitiated polymerization of new (meth)acrylates and ionic liquids was investigated in the presence of ethyl (2,4,6-trimethylbenzoyl) phenylphosphinate (Irgacure® TPO-L) or di(4-methoxybenzoyl)diethylgermane (Ivocerin®) as photoinitiator (PI). Additionally, the results were discussed in comparison with those obtained from commercial 1,6-hexanediol di(meth)acrylate (5 and 6) for deeper investigation of biobased monomer's potential to substitute petroleum derived materials with renewable resources for possible coating applications. Kinetic study shows that methyl 9-(1H-imidazol-1-yl)-10-(methacryloyloxy)octadecanoate / methyl 9-(methacryloyloxy)-10-(1H-imidazol-1-yl)octadecanoate (4) and ionic liquids (1a and 1b) have quantitative conversion after irradiation process which is important for practical applications. On the other hand, heat generation occurs in a longer time during the polymerization of biobased systems or ILs. The poly(meth)acrylates modified from (meth)acrylated fatty acid methyl ester monomers generally show a low glass transition temperature because of the presence of long aliphatic chain in the polymer structure. However, poly(meth)acrylates containing aromatic group have higher glass transition temperature. Therefore, new 4-(4-methacryloyloxyphenyl)-butan-2-one (7) was synthesized which can be a promising candidate for the green techniques, such as light induced polymerization. Photokinetic investigation of the new monomer, 4-(4-methacryloyloxyphenyl)-butan-2-one (7), was discussed using Irgacure® TPO-L or Ivocerin® as photoinitiator. The reactivity of that monomer was compared to commercial 2-phenoxyethyl methacrylate (8) and phenyl methacrylate (9) basis of the differences on monomer structures. The photopolymer of 4-(4-methacryloyloxyphenyl)-butan-2-one (7) might be an interesting candidate for the coating application with the properties of quantitative conversion and high molecular weight. It also shows higher glass transition temperature. In addition to the linear systems based on renewable materials, new crosslinked polymers were also designed in this thesis. Therefore, isomer mixture consisting of ethane-1,2-diyl bis(9-methacryloyloxy-10-hydroxy octadecanoate), ethane-1,2-diyl 9-hydroxy-10-methacryloyloxy-9'-methacryloyloxy10'-hydroxy octadecanoate and ethane-1,2-diyl bis(9-hydroxy-10-methacryloyloxy octadecanoate) (10) was synthesized by derivation of the oleic acid which has not been previously described in the literature. Crosslinked material based on this biobased monomer was produced by photoinitiated free radical polymerization using Irgacure® TPO-L or Ivocerin® as photoinitiator. Furthermore, material properties were diversified by copolymerization of 10 with 4-(4-methacryloyloxyphenyl)-butan-2-one (7) or methyl 9-(1H-imidazol-1-yl)-10-(methacryloyloxy)octadecanoate / methyl 9-(methacryloyloxy)-10-(1H-imidazol-1-yl)octadecanoate (4). In addition to this, influence of comonomer with different chemical structure on the network system was investigated by analysis of thermo-mechanical properties, crosslink density and molecular weight between two crosslink junctions. An increase in the glass transition temperature caused by copolymerization of biobased monomer 10 with the excess amount of 4-(4-methacryloyloxyphenyl)-butan-2-one (7) was confirmed by both techniques, differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). On the other hand, crosslink density decreased as a result of copolymerization reactions due to the reduction in the mean functionality of the system. Furthermore, surface characterization has been tested by contact angle measurements using solvents with different polarity. This work also contributes to the limited data reported about cationic photopolymerization of the epoxidized vegetable oils in the literature in contrast to the widely investigation of thermal curing of the biorenewable epoxy monomers. In addition to the 9,10-epoxystearic acid methyl ester (11), a new monomer of bis-(9,10-epoxystearic acid) 1,2-ethanediyl ester (12) has been synthesized from oleic acid. These two biobased epoxies have been polymerized via cationic photoinitiated polymerization in the presence of bis(t-butyl)-iodonium-tetrakis(perfluoro-t-butoxy)aluminate ([Al(O-t-C4F9)4]-) and isopropylthioxanthone (ITX) as photinitiating system. Polymerization kinetic of 9,10-epoxystearic acid methyl ester (11) and bis-(9,10-epoxystearic acid) 1,2-ethanediyl ester (12) was investigated and compared with the kinetic of commercial monomers being 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexane carboxylate (13), 1,4-butanediol diglycidyl ether (14), and diglycidylether of bisphenol-A (15). Both biobased epoxies (11 and 12) showed higher conversion than cycloaliphatic epoxy (13), and lower reactivity than 1,4-butanediol diglycidyl ether (14). Additional network systems were designed by copolymerization of bis-(9,10-epoxystearic acid) 1,2-ethanediyl ester (12) and diglycidylether of bisphenol-A (15) in different molar ratios (1:1; 1:5; 1:9). It addresses that, final conversion is dependent on polymerization rate as well as physical processes such as vitrification during polymerization. Moreover, low glass transition temperature of homopolymer derived from bis-(9,10-epoxystearic acid) 1,2-ethanediyl ester (12) was successfully increased by copolymerization with diglycidylether bisphenol-A (15). On the other hand, the surface produced from bis-(9,10-epoxystearic acid) 1,2-ethanediyl ester (12) shows hydrophobic character. Higher concentration of biobased diepoxy (12) in the copolymerizing mixture decreases surface free energy. Network systems were also investigated according to the rubber elasticity theory. Crosslinked polymer derived from the mixture of bis-(9,10-epoxystearic acid) 1,2-ethanediyl ester (12) and diglycidylether of bisphenol-A (15) (molar ratio=1:5) exhibits almost ideal polymer network.}, language = {en} } @phdthesis{Izraylit2021, author = {Izraylit, Victor}, title = {Reprogrammable and tunable actuation in multiblock copolymer blends}, doi = {10.25932/publishup-51843}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-518434}, school = {Universit{\"a}t Potsdam}, pages = {104}, year = {2021}, abstract = {Soft actuators have drawn significant attention due to their relevance for applications, such as artificial muscles in devices developed for medicine and robotics. Tuning their performance and expanding their functionality are frequently done by means of chemical modification. The introduction of structural elements rendering non-synthetic modification of the performance possible, as well as control over physical appearance and facilitating their recycling is a subject of a great interest in the field of smart materials. The primary aim of this thesis was to create a shape-memory polymeric actuator, where the capability for non-synthetic tuning of the actuation performance is combined with reprocessability. Physically cross-linked polymeric matrices provide a solid material platform, where the in situ processing methods can be employed for modification of the composition and morphology, resulting in the fine tuning of the related mechanical properties and shape-memory actuation capability. The morphological features, required for shape-memory polymeric actuators, namely two crystallisable domains and anchoring points for physical cross-links, were embedded into a multiblock copolymer with poly(ε-caprolactone) and poly(L-lactide) segments (PLLA-PCL). Here, the melting transition of PCL was bisected into the actuating and skeleton-forming units, while the cross-linking was introduced via PLA stereocomplexation in blends with oligomeric poly(D-lactide) (ODLA). PLLA segment number average length of 12-15 repeating units was experimentally defined to be capable of the PLA stereocomplexes formation, but not sufficient for the isotactic crystallisation. Multiblock structure and phase dilution broaden the PCL melting transition, facilitating its separation into two conditionally independent crystalline domains. Low molar mass of the PLA stereocomplex components and a multiblock structure enables processing and reprocessing of the PLLA-PCL / ODLA blends with common non-destructive techniques. The modularity of the PLLA-PCL structure and synthetic approach allows for independent tuning of the properties of its components. The designed material establishes a solid platform for non-synthetic tuning of thermomechanical and structural properties of thermoplastic elastomers. To evaluate the thermomechanical stability of the formed physical network, three criteria were appraised. As physical cross-links, PLA stereocomplexes have to be evenly distributed within the material matrix, their melting temperature shall not overlap with the thermal transitions of the PCL domains and they have to maintain the structural integrity within the strain ε ranges further applied in the shape-memory actuation experiments. Assigning PCL the function of the skeleton-forming and actuating units, and PLA stereocomplexes the role of physical netpoints, shape-memory actuation was realised in the PLLA-PCL / ODLA blends. Reversible strain of shape-memory actuation was found to be a function of PLA stereocomplex crystallinity, i.e. physical cross-linking density, with a maximum of 13.4 ± 1.5\% at PLA stereocomplex content of 3.1 ± 0.3 wt\%. In this way, shape-memory actuation can be tuned via adjusting the composition of the PLLA-PCL / ODLA blend. This makes the developed material a valuable asset in the production of cost-effective tunable soft polymeric actuators for the applications in medicine and soft robotics.}, language = {en} } @misc{BaldKeller2014, author = {Bald, Ilko and Keller, Adrian}, title = {Molecular processes studied at a single-molecule level using DNA origami nanostructures and atomic force microscopy}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {9}, issn = {1866-8372}, doi = {10.25932/publishup-47584}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-475843}, pages = {13803 -- 13823}, year = {2014}, abstract = {DNA origami nanostructures allow for the arrangement of different functionalities such as proteins, specific DNA structures, nanoparticles, and various chemical modifications with unprecedented precision. The arranged functional entities can be visualized by atomic force microscopy (AFM) which enables the study of molecular processes at a single-molecular level. Examples comprise the investigation of chemical reactions, electron-induced bond breaking, enzymatic binding and cleavage events, and conformational transitions in DNA. In this paper, we provide an overview of the advances achieved in the field of single-molecule investigations by applying atomic force microscopy to functionalized DNA origami substrates.}, language = {en} } @phdthesis{John2021, author = {John, Leonard}, title = {Neuartige DBD-Fluoreszenzfarbstoffe}, doi = {10.25932/publishup-51048}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-510487}, school = {Universit{\"a}t Potsdam}, pages = {257}, year = {2021}, abstract = {Zusammenfassung zur Dissertation „Neuartige DBD-Fluoreszenzfarbstoffe: Synthese, Untersuchungen und Anwendungen" von Leonard John In dieser Arbeit konnten auf Basis der etablierten [1,3]-Dioxolo[4,5-f][1,3]benzodioxol (DBD) Fluoreszenzfarbstoffe zwei neue Konzepte zur Darstellung unsymmetrisch funktionalisierter DBD-Fluorophore entwickelt werden. Die Variation der elektronenziehenden Reste f{\"u}hrte zu einer Erweiterung des Farbspektrums an DBD-Fluorophoren, wobei alle weiteren spektroskopischen Parameter (Fluoreszenzlebenszeit, -quantenausbeute und STOKES-Verschiebung) unver{\"a}ndert hohe Werte aufweisen. Neben der Variation der elektronenziehenden Reste wurde das "pi"-System des DBD-Farbstoffs mit der Einf{\"u}hrung von Stilben-, und Tolan-Derivaten vergr{\"o}ßert. Stilben-Derivate zeigten {\"a}hnlich gute spektroskopische Eigenschaften wie die bereits etablierten DBD-Farbstoffe. Fluorophore mit langwelliger Emission sind auf Grund der großen Gewebe-Eindringtiefe besonders interessant f{\"u}r biologische Anwendungen. Da der langwelligste Vertreter der O4-DBD-Farbstoffe in polaren Medien nur schwer l{\"o}slich ist, wurde ein Weg zur Einf{\"u}hrung l{\"o}slichkeitsvermittelnder Gruppen gesucht. Hierbei fiel die Wahl auf eine Carbons{\"a}ure-Gruppe zur Steigerung der Hydrophilie. Eine von vier untersuchten Methoden erwies sich als zielf{\"u}hrend, sodass das gew{\"u}nschte Molek{\"u}l isoliert werden konnte. Eine erh{\"o}hte Wasserl{\"o}slichkeit wurde allerdings nicht beobachtet. Zur Erforschung von Fettstoffwechselkrankheiten wie der ALZHEIMER-Krankheit werden fluoreszenzmarkierte Lipide ben{\"o}tigt. Um unterschiedliche Bereiche einer Membran zu untersuchen, war das Ziel, den Fluorophor an unterschiedlichen Stellen innerhalb der Fetts{\"a}ure zu lokalisieren. Hierbei sollte die Gesamtkettenl{\"a}nge des DBD-Lipids einer C18-Kette, analog der Stearins{\"a}ure, entsprechen. Durch die stufenweise Einf{\"u}hrung der Reste gelang es, drei DBD-Lipide herzustellen, wobei sich der Fluorophor an unterschiedlichen Positionen innerhalb der Kette befindet. Die photophysikalischen Eigenschaften der Lipide weichen nur marginal von denen der reinen Fluorophore ab. Eine Einlagerung in giant unilamellar vesicles (GUVs) konnte f{\"u}r zwei Derivate beobachtet werden, wobei keine dom{\"a}nenspezifisch war. Ein weiteres Ziel dieser Arbeit war es, die vier Sauerstoffatome im DBD-Grundk{\"o}rper stufenweise durch Schwefelatome zu ersetzen und die Ringgr{\"o}ßen des DBD-Fluorophors zu variieren. F{\"u}r die Ringgr{\"o}ße zeigte der 1,2-S2-DBD mit jeweils zwei F{\"u}nfringen die besten spektroskopischen Eigenschaften. Durch die Synthese von zwei weiteren schwefelhaltigen DBD-Grundk{\"o}rpern (S1- und 1,4-S2-DBD) konnten insgesamt drei neue Farbstoffklassen zug{\"a}nglich gemacht werden. F{\"u}r alle neuen Chromophore wurden elektronenziehende Reste (Aldehyd, Acyl, Ester, Carboxy) eingef{\"u}hrt und die jeweiligen Derivate spektroskopisch untersucht. Mit steigender Anzahl an Schwefel-Atomen im Grundk{\"o}rper zeigt sich eine bathochrome Verschiebung der Emission, wobei die Werte f{\"u}r die Fluoreszenzlebenszeit- und -quantenausbeute abnehmen. Die optimalen spektroskopischen Eigenschaften aus langwelliger Emission, hoher Fluoreszenzlebenszeit und -quantenausbeute zeigt das 1,4-S2-Dialdehyd-Derivat. F{\"u}r die S1- und 1,2-S2-Dialdehyd- Derivate wurden Konzepte entwickelt, um bioreaktive Reste (Alkin, HOSu, Maleimid) einzuf{\"u}hren und die Fluorophore in biologischen Systemen anwenden zu k{\"o}nnen.}, language = {de} } @phdthesis{Kaestner2021, author = {Kaestner, Pia Isabel}, title = {Neue Polymermaterialien auf der Basis von funktionalisierten ionischen Fl{\"u}ssigkeiten zur potentiellen Anwendung in Membranen}, doi = {10.25932/publishup-50940}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-509403}, school = {Universit{\"a}t Potsdam}, pages = {VI, 164}, year = {2021}, abstract = {Die vorliegende Arbeit thematisiert die Synthese und Charakterisierung von neuen funktionalisierten ionischen Fl{\"u}ssigkeiten und deren Polymerisation. Die ionischen Fl{\"u}ssigkeiten wurden dabei sowohl mit polymerisierbaren Kationen als auch Anionen hergestellt. Zum einen wurden bei thermisch initiierten Polymerisationen Azobis(isobutyronitril) (AIBN) verwendet und zum anderen dienten bei photochemisch initiierten Polymerisationen Bis-4-(methoxybenzoyl)diethylgermanium (Ivocerin®) als Radikalstarter. Mittels Gelpermeationschromatographie konnte das Homopolymer Polydimethylaminoethylmethacrylat untersucht werden, welches erst im Anschluss an die GPC-Messungen polymeranalog modifiziert wurde. Dabei wurden nach einer Quaternisierung und anschließender Anionenmetathese bei diesen Polymeren die Grenzviskosit{\"a}ten bestimmt und mit den Grenzviskosit{\"a}ten der direkt polymerisierten ionischen Fl{\"u}ssigkeiten verglichen. Bei der direkten Polymerisation von Poly(N-[2-(Methacryloyloxy)ethyl]-N-butyl-N,N-dimethyl-ammoniumbis(trifluormethylsulfonyl)imid) lag [η_Huggins] bei 100 mL/g und bei dem polymeranalog hergestellten Polymer betrug [η_Huggins] = 40 mL/g. Die ionischen Fl{\"u}ssigkeiten mit polymerisierbaren funktionellen Gruppen wurden mittels Photo-DSC hinsichtlich der maximalen Polymerisationsgeschwindigkeit (Rpmax), der Zeit, in der dieses Maximum erreicht wurde, tmax, ihrer Glas{\"u}berganstemperatur (Tg) und des Umsatzes an Vinylprotonen untersucht. Bei diesen Messungen wurde zum einen der Einfluss der unterschiedlichen Alkylkettenl{\"a}nge am Ammoniumion und der Einfluss von verschiedenen Anionen bei gleichbleibender Kationenstruktur analysiert. So polymerisierte das ethylsubstituierte Kation mit einer tmax von 21 Sekunden am langsamsten. Die maximale Polymerisationsgeschwindigkeit (Rpmax) betrug 3.3∙10-2 s-1. Die tmax Werte der {\"u}brigen alkylsubstituierten ionischen Fl{\"u}ssigkeiten mit einer polymerisierbaren funktionellen Gruppe hingegen lagen zwischen 10 und 15 Sekunden. Die Glas{\"u}bergangstemperaturen der mittels photoinduzierter Polymerisation hergestellten Polymere lagen mit 44 bis 55 °C nahe beieinander. Alle Monomere zeigten einen hohen Umsatz der Vinylprotonen; er betrug zwischen 93 und 100\%. Mithilfe einer Bandanlage, ausger{\"u}stet mit einer LED (λ = 395 nm), konnten Polymerfilme hergestellt werden. Der Umsatz an Doppelbindungs{\"a}quivalenten dieser Filme wurde anhand der 1H-NMR Spektroskopie bestimmt. Bei der dynamisch-mechanischen Analyse wurden die Polymerfilme mit einer konstanten Heizrate und Frequenz periodisch wechselnden Beanspruchungen ausgesetzt, um die Glas{\"u}bergangstemperaturen zu bestimmen. Die niedrigste Tg mit 26 °C besaß das butylsubstituierte N-[2-(Methacryloyloxy)ethyl]-N-butyl-N,N-dimethyl-ammoniumbis(trifluormethylsulfonyl)imid, welches als Polymerfilm mit Ivocerin® als Initiator hergestellt wurde, wohingegen die h{\"o}chste Tg bei dem gleichen Polymer, welches direkt durch freie radikalische Polymerisation der ionischen Fl{\"u}ssigkeit in Masse mit AIBN hergestellt wurde, 51 °C betrug. Zus{\"a}tzlich wurden die Filme unter dem Aspekt der Topographie mit einem Rasterkraftmikroskop untersucht, welches eine Dom{\"a}nenstruktur des Polymers N-[2-(methacryloyloxy)ethyl]-N-butyl-N,N-dimethyl-ammonium tris(pentafluorethyl)trifluorphosphat offenbarte.}, language = {de} } @phdthesis{Czarnecki2021, author = {Czarnecki, Maciej}, title = {Untersuchungen zur Synthese von (1,7)-Naphthalenophanen {\"u}ber eine Dehydro-DIELS-ALDER-Reaktion als Schl{\"u}sselschritt}, doi = {10.25932/publishup-50867}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-508670}, school = {Universit{\"a}t Potsdam}, pages = {vii, 227, XXX}, year = {2021}, abstract = {Die vorliegende Dissertation behandelt drei thematische Schwerpunkte. Im Ergebnisteil steht die chemische Synthese von sogenannten (1,7)-Naphthalenophanen im Vordergrund, die zur Substanzklasse von Cyclophanen geh{\"o}ren. W{\"a}hrend zahlreiche Synthesemethoden Strategien zum Aufbau von Ringsystemen (wie z. B. von Naphthalenophanen) verfolgen, die Teil einer bereits existierenden aromatischen Struktur der Ausgangsverbindung sind, nutzen nur wenige Ans{\"a}tze Reaktionen, die einen Ringschluss zum gew{\"u}nschten Produkt erst im Zuge der Synthese etablieren. Eine Benzanellierung, die eine besondere Aufmerksamkeit im Arbeitskreis erfahren hat, ist die Dehydro-DIELS-ALDER-Reaktion (DDA-Reaktion). Im Rahmen dieser Arbeit konnte gezeigt werden, dass zw{\"o}lf ausgew{\"a}hlte (1,7)-Naphthalenophane, die teilweise ringgespannt und makrozyklisch aufgebaut waren, mithilfe einer photochemischen Variante der DDA-Reaktion (PDDA-Reaktion) zug{\"a}nglich gemacht werden k{\"o}nnen. Die Versuche, auf thermischem Wege (TDDA-Reaktion) (1,7)-Naphthalenophane herzustellen, misslangen. Die außergew{\"o}hnliche Reaktivit{\"a}t der Photoreaktanten konnte mithilfe quantenchemischer Berechnungen durch eine gefaltete Grundzustandsgeometrie erkl{\"a}rt werden. Dar{\"u}ber hinaus wurden Ringspannungen und strukturelle Spannungsindikatoren der relevanten Photoprodukte ermittelt und Trends in Abh{\"a}ngigkeit der Linkerl{\"a}nge in den NMR-Spektren der Zielverbindungen ermittelt sowie diskutiert. Zudem zeigte eine Variation am Chromophor (Acyl-, Carbons{\"a}ure- und Carbons{\"a}ureester) der Photoreaktanten bei der Bestrahlung in Dichlormethan eine vergleichbare Photokinetik und -reaktivit{\"a}t. Der zweite Abschnitt dieser Dissertation ist dem Design und der Entwicklung zweier Photoreaktoren f{\"u}r UV-Anwendungen im kontinuierlichen Durchfluss gewidmet, da photochemische Transformationen bekanntermaßen in ihrer Skalierbarkeit limitiert sind. Im ersten Prototyp konnten mittels effizienter Parallelschaltung mit bis zu drei UV-Lampen (𝜆𝜆 = 254, 310 und 355 nm) Produktmaterialmengen von bis zu n = 188 mmol anhand eines ausgew{\"a}hlten Fallbeispiels erreicht werden. Im konstruktionstechnisch stark vereinfachten zweiten Photoreaktor wurden alle quarzhaltigen Elemente gegen g{\"u}nstigeres PLEXIGLAS® ersetzt. Das Resultat waren identische Raum-Zeit-Ausbeuten in Bezug auf das zuvor gew{\"a}hlte Synthesebeispiel. Demnach bietet die UV-Photochemie im kontinuierlichen Durchfluss Vorteile gegen{\"u}ber der traditionellen Bestrahlung im Tauchreaktor. Hinsichtlich Reaktionszeit, Produktausbeuten und L{\"o}semittelverbrauch ist sie synthetisch weit {\"u}berlegen. Im letzten Abschnitt der Arbeit wurden diese Erkenntnisse genutzt, um biomedizinisch und pharmakologisch vielversprechende 1-Arylnaphthalen-Lignane mittels einer intramolekularen PDDA-Reaktion (IMPDDA-Reaktion) als Schl{\"u}sselschritt herzustellen. Hierzu wurden drei Konzepte erarbeitet und in der Totalsynthese von drei ausgew{\"a}hlten Zielstrukturen auf Basis des 1-Arylnaphthalengrundger{\"u}sts realisiert.}, language = {de} } @phdthesis{Ebel2021, author = {Ebel, Kenny}, title = {Quantification of low-energy electron induced single and double strand breaks in well-defined DNA sequences using DNA origami nanostructures}, doi = {10.25932/publishup-50449}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-504499}, school = {Universit{\"a}t Potsdam}, pages = {111}, year = {2021}, abstract = {Ionizing radiation is used in cancer radiation therapy to effectively damage the DNA of tumors leading to cell death and reduction of the tumor tissue. The main damage is due to generation of highly reactive secondary species such as low-energy electrons (LEE) with the most probable energy around 10 eV through ionization of water molecules in the cells. A simulation of the dose distribution in the patient is required to optimize the irradiation modality in cancer radiation therapy, which must be based on the fundamental physical processes of high-energy radiation with the tissue. In the present work the accurate quantification of DNA radiation damage in the form of absolute cross sections for LEE-induced DNA strand breaks (SBs) between 5 and 20 eV is done by using the DNA origami technique. This method is based on the analysis of well-defined DNA target sequences attached to DNA origami triangles with atomic force microscopy (AFM) on the single molecule level. The present work focuses on poly-adenine sequences (5'-d(A4), 5'-d(A8), 5'-d(A12), 5'-d(A16), and 5'- d(A20)) irradiated with 5.0, 7.0, 8.4, and 10 eV electrons. Independent of the DNA length, the strand break cross section shows a maximum around 7.0 eV electron energy for all investigated oligonucleotides confirming that strand breakage occurs through the initial formation of negative ion resonances. Additionally, DNA double strand breaks from a DNA hairpin 5'-d(CAC)4T(Bt-dT)T2(GTG)4 are examined for the first time and are compared with those of DNA single strands 5'-d(CAC)4 and 5'- d(GTG)4. The irradiation is made in the most likely energy range of 5 to 20 eV with an anionic resonance maximum around 10 eV independently of the DNA sequence. There is a clear difference between σSSB and σDSB of DNA single and double strands, where the strand break for ssDNA are always higher in all electron energies compared to dsDNA by the factor 3. A further part of this work deals with the characterization and analysis of new types of radiosensitizers used in chemoradiotherapy, which selectively increases the DNA damage upon radiation. Fluorinated DNA sequences with 2'-fluoro-2'-deoxycytidine (dFC) show an increased sensitivity at 7 and 10 eV compared to the unmodified DNA sequences by an enhancement factor between 2.1 and 2.5. In addition, light-induced oxidative damage of 5'-d(GTG)4 and 5'-d((CAC)4T(Bt-dT)T2(GTG)4) modified DNA origami triangles by singlet oxygen 1O2 generated from three photoexcited DNA groove binders [ANT994], [ANT1083] and [Cr(ddpd)2][BF4]3 illuminated in different experiments with UV-Vis light at 430, 435 and 530 nm wavelength is demonstrated. The singlet oxygen induced generation of DNA damage could be detected in both aqueous and dry environments for [ANT1083] and [Cr(ddpd)2][BF4]3.}, language = {en} } @misc{SchwarzeRiemerMuelleretal.2019, author = {Schwarze, Thomas and Riemer, Janine and M{\"u}ller, Holger and John, Leonard and Holdt, Hans-J{\"u}rgen and Wessig, Pablo}, title = {Na+ Selective Fluorescent Tools Based on Fluorescence Intensity Enhancements, Lifetime Changes, and on a Ratiometric Response}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1136}, issn = {1866-8372}, doi = {10.25932/publishup-43748}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-437482}, pages = {13}, year = {2019}, abstract = {Over the years, we developed highly selective fluorescent probes for K+ in water, which show K+-induced fluorescence intensity enhancements, lifetime changes, or a ratiometric behavior at two emission wavelengths (cf. Scheme 1, K1-K4). In this paper, we introduce selective fluorescent probes for Na+ in water, which also show Na+ induced signal changes, which are analyzed by diverse fluorescence techniques. Initially, we synthesized the fluorescent probes 2, 4, 5, 6 and 10 for a fluorescence analysis by intensity enhancements at one wavelength by varying the Na+ responsive ionophore unit and the fluorophore moiety to adjust different K-d values for an intra- or extracellular Na+ analysis. Thus, we found that 2, 4 and 5 are Na+ selective fluorescent tools, which are able to measure physiologically important Na+ levels at wavelengths higher than 500 nm. Secondly, we developed the fluorescent probes 7 and 8 to analyze precise Na+ levels by fluorescence lifetime changes. Herein, only 8 (K-d=106 mm) is a capable fluorescent tool to measure Na+ levels in blood samples by lifetime changes. Finally, the fluorescent probe 9 was designed to show a Na+ induced ratiometric fluorescence behavior at two emission wavelengths. As desired, 9 (K-d=78 mm) showed a ratiometric fluorescence response towards Na+ ions and is a suitable tool to measure physiologically relevant Na+ levels by the intensity change of two emission wavelengths at 404 nm and 492 nm.}, language = {en} } @misc{BauchFudickarLinker2021, author = {Bauch, Marcel and Fudickar, Werner and Linker, Torsten}, title = {Stereoselective [4+2] Cycloaddition of Singlet Oxygen to Naphthalenes Controlled by Carbohydrates}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1116}, issn = {1866-8372}, doi = {10.25932/publishup-49336}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-493361}, pages = {19}, year = {2021}, abstract = {Stereoselective reactions of singlet oxygen are of current interest. Since enantioselective photooxygenations have not been realized efficiently, auxiliary control is an attractive alternative. However, the obtained peroxides are often too labile for isolation or further transformations into enantiomerically pure products. Herein, we describe the oxidation of naphthalenes by singlet oxygen, where the face selectivity is controlled by carbohydrates for the first time. The synthesis of the precursors is easily achieved starting from naphthoquinone and a protected glucose derivative in only two steps. Photooxygenations proceed smoothly at low temperature, and we detected the corresponding endoperoxides as sole products by NMR. They are labile and can thermally react back to the parent naphthalenes and singlet oxygen. However, we could isolate and characterize two enantiomerically pure peroxides, which are sufficiently stable at room temperature. An interesting influence of substituents on the stereoselectivities of the photooxygenations has been found, ranging from 51:49 to up to 91:9 dr (diastereomeric ratio). We explain this by a hindered rotation of the carbohydrate substituents, substantiated by a combination of NOESY measurements and theoretical calculations. Finally, we could transfer the chiral information from a pure endoperoxide to an epoxide, which was isolated after cleavage of the sugar chiral auxiliary in enantiomerically pure form.}, language = {en} } @misc{MachatschekSchoeneRaschdorfetal.2019, author = {Machatschek, Rainhard Gabriel and Sch{\"o}ne, Anne-Christin and Raschdorf, Elisa and Ihlenburg, Ramona and Schulz, Burkhard and Lendlein, Andreas}, title = {Interfacial properties of morpholine-2,5-dione-based oligodepsipeptides and multiblock copolymers}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1106}, issn = {1866-8372}, doi = {10.25932/publishup-46975}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-469755}, pages = {170 -- 180}, year = {2019}, abstract = {Oligodepsipeptides (ODPs) with alternating amide and ester bonds prepared by ring-opening polymerization of morpholine-2,5-dione derivatives are promising matrices for drug delivery systems and building blocks for multifunctional biomaterials. Here, we elucidate the behavior of three telechelic ODPs and one multiblock copolymer containing ODP blocks at the air-water interface. Surprisingly, whereas the oligomers and multiblock copolymers crystallize in bulk, no crystallization is observed at the air-water interface. Furthermore, polarization modulation infrared reflection absorption spectroscopy is used to elucidate hydrogen bonding and secondary structures in ODP monolayers. The results will direct the development of the next ODP-based biomaterial generation with tailored properties for highly sophisticated applications.}, language = {en} } @misc{JiangMansfeldKratzetal.2019, author = {Jiang, Yi and Mansfeld, Ulrich and Kratz, Karl and Lendlein, Andreas}, title = {Programmable microscale stiffness pattern of flat polymeric substrates by temperature-memory technology}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, volume = {9}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1}, issn = {1866-8372}, doi = {10.25932/publishup-46974}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-469745}, pages = {181 -- 188}, year = {2019}, abstract = {Temperature-memory technology was utilized to generate flat substrates with a programmable stiffness pattern from cross-linked poly(ethylene-co-vinyl acetate) substrates with cylindrical microstructures. Programmed substrates were obtained by vertical compression at temperatures in the range from 60 to 100 degrees C and subsequent cooling, whereby a flat substrate was achieved by compression at 72 degrees C, as documented by scanning electron microscopy and atomic force microscopy (AFM). AFM nanoindentation experiments revealed that all programmed substrates exhibited the targeted stiffness pattern. The presented technology for generating polymeric substrates with programmable stiffness pattern should be attractive for applications such as touchpads. optical storage, or cell instructive substrates.}, language = {en} }