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Responsive fluorescent materials offer a high potential for sensing and (bio-)imaging applications. To investigate new concepts for such materials and to broaden their applicability, the previously reported non-fluorescent zinc(II) complex [Zn(L)] that shows coordination-induced turn-on emission was encapsulated into a family of non-fluorescent polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) diblock copolymer micelles leading to brightly emissive materials. Coordination-induced turn-on emission upon incorporation and ligation of the [Zn(L)] in the P4VP core outperform parent [Zn(L)] in pyridine solution with respect to lifetimes, quantum yields, and temperature resistance. The quantum yield can be easily tuned by tailoring the selectivity of the employed solvent or solvent mixture and, thus, the tendency of the PS-b-P4VP diblock copolymers to self-assemble into micelles. A medium-dependent off-on sensor upon micelle formation could be established by suppression of non-micelle-borne emission background pertinent to chloroform through controlled acidification indicating an additional pH-dependent process.

A series of cationic diblock copolymers were synthesized via sequential anionic polymerization of 2-vinylpyridine and ethylene oxide and further quaternization of the resulting diblock copolymers with dimethyl sulfate. Diblock copolymers with a degree of polymerization (DP) of the cationic block equal to 40 and DP of the poly(ethylene oxide) (PEO) block equal to 45, 210 and 450, as well as a cationic homopolymer with DP = 40 (control), were adsorbed on the surface of anionic liposomes of 40–60 nm in diameter. The liposomes were constructed with egg lecithin admixed with 0.1 mole fraction of a doubly anionic lipid, cardiolipin. The liposome–polymer complexes were characterized using electrophoretic mobility measurements, dynamic light scattering, conductivity, fluorescence and UV spectroscopy, and differential scanning calorimetry. Adsorption of the polymers causes the liposomes to aggregate; the only exception is the diblock copolymer with DP of the PEO block of 450, which shows an aggregation-preventing effect. In all cases, the integrity of liposomes is retained upon their complexation with polymers. The diblock copolymer with a short PEO block induces clustering of anionic lipid in the outer leaflet of the membrane; this effect becomes less pronounced with increasing DP of the PEO block. The differences in behaviour of the diblock copolymers are explained in terms of copolymer cluster formation via hydrogen bonding between neighbouring PEO blocks. These observations are important for interpretation of biological effects produced by cationic polymers and selection of cationic polymers for biomedical applications. © 2017 Society of Chemical Industry

Oxidative thermal removal of the polymeric templates is not trivial for molybdenum oxides and hampers mesostructuring of this material. At ambient oxygen fugacity, MoVI is the thermodynamically stable oxidation state and sublimation of MoO3 leads to a quick loss of the mesostructure through Oswald ripening. Taking advantage of the Boudouard equilibrium allows to fix the oxygen fugacity at a level where non-volatile MoO2−x is stable while carbonaceous material may be oxidized by CO2. Mesostructured MoO2−x can be chemically converted into MoO3 or MoN under retention of the mesostructure.

Die heterogene Katalyse an tragerfixierten Nanopartikeln (NP) ist ein uberaus attraktives Forschungsfeld. Eine der grosten Herausforderungen ist jedoch weiterhin die effiziente Stabilisierung der NP ohne Einschrankung ihrer katalytischen Aktivitat. Durch eine Kombination bekannter Top-down- (koaxiales Elektrospinnen) und Bottom-up-Methoden (kristallisationsinduzierte Selbstassemblierung) ist es uns gelungen, Fasermatten mit funktionellen, nanometergrosen Kompartimenten (Patches) auf der Oberflache herzustellen. Diese Patches sind in der Lage, Gold-Nanopartikel (AuNP) selektiv zu binden und zu stabilisieren. Die mit AuNP beladenen Hybridfasermatten zeigten in der Alkoholyse von Dimethylphenylsilan bereits nach vergleichsweise kurzen Reaktionszeiten sowie unter milden Bedingungen quantitativen Umsatz. Die exzellente Wiederverwendbarkeit zeigt sich darin, dass selbst nach 10 aufeinanderfolgenden Zyklen keine Reduktion der katalytischen Aktivitat oder ein “Ausbluten” von Gold beobachtet werden konnte. Die Flexibilitat der vorgestellten Methode erlaubt eine einfache Ubertragung auf andere Tragerfasern und unterschiedliche katalytisch aktive NP, wodurch sich ein breites Anwendungsspektrum in der heterogenen Katalyse eroffnet.

Polymer blends have the potential to be homogenously foamed, since the interface area between their phases can be used as bubble nucleating agents during the foaming process. Immiscible polymer blends of poly(2,6-dimethyl-1,4-phenylene ether) PPE and poly(styrene-co-acrylonitrile) SAN with a weight ratio of 60/40 are compatibilized by different amounts (1–10 wt%) of Janus nanoparticles (JPs). Here, we report on the nucleation effect of JPs and the dispersed PPE phase on the foaming behavior of PPE/SAN blends. The plasticization of CO2 and its solubility and diffusion behavior in the PPE/SAN blend are analyzed and correlated to blend morphologies. It is shown that partial coverage of the raspberry structure results in stress concentration at the blend interface during the saturation step. This formation of new surfaces by cleavage (and maybe microcrazes) results in a higher sorption of the blowing agent, which affects the foaming behavior. Through temperature-induced batch foaming with CO2, the blends are foamed to find the optimum foaming conditions and relationships between the morphology of the compact and foamed blends (cellular structure) and the density are established. Finally, it was concluded that by using Janus particles, homogenous foams with small cell sizes, and relatively high densities are produced.

Eine neue, Templat-gestutzte Synthese monodisperser Nanopartikel stellt keine Anforderungen an die Selbstorganisation und ist hoch reproduzierbar. Hierzu werden masgeschneiderte Polymerkafige fur die Synthese von Nanopartikeln verwendet, die aus vernetzten Makromolekulen mit Thiolendgruppen bestehen. Goldnanopartikel (AuNPs) wurden in verschiedenen Verhaltnissen von Polymerkafig zu Gold in situ in den Polymerkafigen synthetisiert. Die Polymerkafige zeichneten sich dabei durch eine definierte Beladungskapazitat aus, mit exzellenter Kontrolle uber Form und Grose. Dagegen zeigten Kontrollversuche mit linearen Diblockcopolymeren einen linearen Anstieg der Partikelgrosen mit steigendem Goldanteil. Das unterschiedliche Wachstumsverhalten der AuNPs wird durch die Vernetzungsgrad-abhangige Flexibilitat der Polymerketten erklart. Des Weiteren wird die Polymerkafig-gesteuerte In-situ-Synthese auf Silber- (AgNPs), Palladium- (PdNPs) und Platinnanopartikel (PtNPs) ubertragen.

A series of strong polycations is synthesized through the anionic polymerization of 2-vinylpyridine, followed by subsequent quaternization of the resulting polymer. Polycations based on quaternized 2-vinylpyridine (PVPQs) with degrees of polymerization (DP) from 20 to 440 are adsorbed on the surface of small anionic liposomes. Liposome/PVPQ complexes are characterized by using a number of physicochemical methods. All PVPQs are totally adsorbed onto the liposome surface up to a certain concentration at which saturation is reached (which is specific for each PVPQ). The integrity of the adsorbed liposomes remains intact. Short PVPQs interact with anionic lipids localized on the outer membrane leaflet, whereas long PVPQs extract anionic lipids from the inner to outer leaflet. Complexes tend to aggregate, and the largest aggregates are formed when the initial charge of the liposomes is fully neutralized by the charge of the PVPQ. PVPQs with intermediate DPs demonstrate behavioral features of both short and long PVPQs. These results are important for the interpretation of the biological effects of cationic polymers and the selection of cationic polymers for biomedical applications.

The carbon content of mesostructured organic-inorganic hybrid material of a cylindrical block copolymer template of poly(2-vinylpyridine)-block-poly(allyl methacrylate) (P2VP-b-PAMA) and ammonium paramolybdate (APM) could be reduced by thermal depolymerization. By calcination in vacuo at 320 °C the PAMA core can be completely removed while the remaining P2VP brush preserves the mesostructure. The P2VP-APM composite can then be carburized in-situ to MoOxCy in a second pyrolysis step without any additional carbon source but P2VP. The molybdenum oxycarbide nanotubes obtained, form hierarchically porous non-woven structures, which were tested as catalyst in the decomposition of NH3. They proved to be catalytically active at temperatures above 450 °C. The activation energy was estimated from an Arrhenius Plot to be 127 kJ·mol–1.

Polymer-Nanorohrchen mit eingeschlossenen Goldnanopartikeln wurden uber den “Tubes by Fiber Templates”(TUFT)-Prozess hergestellt und als Teebeutel-ahnliches Katalysatorsystem verwendet. Dazu wurden zunachst Poly(L-lactid)-stabilisierte Goldnanopartikel synthetisiert und mit freiem Poly(L-lactid) zu Komposit-Nanofasern elektrogesponnen. Anschliesend wurde das Faservlies aus der Gasphase mit Poly(p-xylylen) beschichtet, und die inneren Templatfasern wurden durch Pyrolyse entfernt. Die so hergestellten Polymer-Rohrchen enthielten immobilisierte Goldnanopartikel und zeigten eine hohe katalytische Aktivitat bezuglich der hydrolytischen Oxidation von Dimethylphenylsilan sowie der entsprechenden Alkoholyse mit n-Butanol. Das makroskopische Rohrchenvlies konnte zur Katalyse analog zu einem Teebeutel verwendet werden und zeigte eine hervorragende Wiederverwendbarkeit.

Gold-containing polymer nanotubes, which showed both catalytic activity and resistance to leaching, were prepared by the "tubes by fiber templates" (TUFT) process. For this purpose, electrospun polymer nonwovens with incorporated poly(L-lactide)-stabilized gold nanoparticles were coated with poly(p-xylylene) by the chemical vapor deposition process, and then the inner fiber templates were removed. The resulting polymer tubes carried encapsulated gold nanoparticles which were shown to be immobilized and featured pronounced catalytic activity towards the hydrolytic oxidation of dimethylphenylsilane and the alcoholysis of dimethylphenylsilane with n-butanol. The macroscopic nonwovens could be used as tea-bag-like catalyst systems and showed excellent reusability.

Living Micrococcus luteus (M. luteus) and Escherichia coli (E. coli) are encapsulated in poly(vinyl alcohol), poly(vinylpyrrolidone), hydroxypropyl cellulose, and gelatin by high-temperature spray drying. The challenge is the survival of the bacteria during the standard spray-drying process at temperatures of 150 °C (M. luteus) and 120 °C (E. coli). Raman imaging and transmission electron microscopy indicate encapsulated bacteria in hollow composite microparticles. The versatility of the spray-dried polymer bacteria microparticles is successfully proved by standard polymer solution-processing techniques such as electrospinning, even with harmful solvents, to water-insoluble polyacrylonitrile, polystyrene, poly(methyl methacrylate), and poly(vinyl butyrate) nanofiber nonwovens, which opens numerous new opportunities for novel applications.

Aqueous solutions of a double responsive P2VP62-b-PEO452-b-P(GME36-co-EGE36) triblock terpolymer were investigated by means of small-angle neutron scattering (SANS) in order to derive information about structural changes going along with the temperature triggered gel-sol-gel transition at pH = 7, and the sol-gel transition at pH = 3.5, respectively, observed by rheology. SANS measurements on dilute samples at different pH and temperature confirmed the formation of core-shell-corona micelles under conditions, where only one of the outer blocks is insoluble. In addition, temperature-dependent scattering experiments were performed for higher volume fractions, that is, the concentration range where hydrogels were formed. This allowed us to identify the structural transitions, being responsible for the gel-sol-gel transition at pH = 7, and the structure of the gel phase formed at low pH and elevated temperatures.

The synthesis of several diblock copolymers with DMAEMA via anionic polymerization is presented; PS-b-PDMAEMA, PB-b-PDMAEMA, poly(p-tert-butoxystyrene)-b-PDMAEMA, and PEO-b-PDMAEMA. The latter was synthesized using sec-butyllithium as initiator in presence of the phosphazene base t-BuP 4 , enabling a facile changeover from an oxyanion to a carbanion. All reactions resulted in narrowly distributed block copolymers (PDI < 1.1). For PEO-b-PDMAEMA, diblock copolymers with a high blocking efficiency and a near-narrow molecular weight distribution (PDI < 1.40) could be prepared. The advantage of the presented one-pot synthesis is a significant higher blocking efficiency compared to commercially available PEO macroinitiators under similar conditions.

Immiscible blends of poly(2,6-dimethyl-1,4-phenylene ether)/poly(styrene-co-acrylonitrile) (PPE/SAN) were batch-foamed using CO2 as a blowing agent as a function of foaming temperature, foaming time, and blend composition. Evaluation of the resulting cellular morphology revealed an enhanced foamability of SAN with PPE contents up to 20 wt% as indicated by a similar volume expansion but a significantly reduced mean cell size. This behavior is related to a heterogeneous nucleation activity by the dispersed PPE phase. A further increasing PPE content, however, leads to increasing foam densities as well as nonuniform foam morphologies. The changes in the foaming behavior can be correlated with the melt rheological properties and the corresponding blend morphology. Shear-rheological investigations revealed an onset of percolation of the dispersed PPE phase between 20 and 40 wt%, and a transition towards cocontinuity at 60 wt%. The materials response under uniaxial elongational flow, as assessed by Rheotens measurements, revealed an increase in elongational viscosity scaling with the PPE content, similar to the shear data. However, the strain hardening behavior was reduced by increasing PPE contents and, at 20 wt%, the drawability revealed a significant drop-both phenomena limiting the foamability of polymers. In summary, the present study discusses fundamental aspects of foaming immiscible PPE/SAN blends. POLYM. ENG. SCI., 48:2111–2125, 2008. © 2008 Society of Plastics Engineers

The isothermal crystallization kinetics of PEO and PE blocks within various triblock terpolymers were studied by DSC. The effect of the geometry of the microdomains was analyzed by studying different compositions of PE-b-PS-b-PEO triblock terpolymers. The crystallization rate decreased for decreasing block content for both crystallizable blocks. The effect of the microdomain geometry, confinement or chain tethering on the crystallization of PEO was extensively studied by comparing pairs of triblock terpolymers with differences either in the nature (crystalline, glassy, amorphous) or in the location of the other blocks in the terpolymer.

A first attempt was made to produce novel ABC triblock terpolymers with three potentially crystallisable blocks: polyethylene (PE), poly(ethylene oxide) (PEO), and poly(e-caprolactone) (PCL). Polybutadiene-b-poly(ethylene oxide) diblock copolymers were synthesized by living anionic polymerization. Then, a non-catalyzed thermal polymerization of e-caprolactone from the hydroxyl end group of the PB-b-PEO diblock precursors was performed. Finally, hydrogenation by Wilkinson catalyst produced PE-b-PEO-b-PCL triblock terpolymers. Side reactions were detected that lead to the formation of undesired PCL-b-PEO diblock copolymers, however, these impurities were successfully removed by purification. A range of triblock terpolymers with PCL and PEO minor components were prepared. Topological restrictions on the PEO middle block prevented this block from crystallizing while the complex crystallization behavior of the PE and PCL blocks was documented by DSC and WAXS measurements.

Fourier-transform near-infrared (FT-NIR) fiber-optic spectroscopy was successfully used to monitor the anionic polymerization of ethylene oxide (EO). Kinetic data are provided for the polymerization of EO with the sec-BuLi/Bu t P 4 initiating system under different initiators and reaction conditions on the polymerization of EO is investigated. Online monitoring using NIR spectroscopy revals an unexpected induction period present in EO homopolymerizations as well as in the synthesis of PEO containing block copolymers with [Li/Bu t P 4 ] + counterions. The resulting polymers are characterized by size exclusion chromatography (SEC). A low-molecular-weight polystyrene-block-poly(ethyelen oxide) (PS-b-PEO) diblock copolymer was synthesized to gain more insight into the observed induction period by matrix-assisted laser desorption ionization time-of-flight mass spectrometrhy (MALDI-ToF MS) on samples taken during EO polymerization. The induction period is believed to be a result of different factors involved in the formation of active centers, for example, the break up of lithium alkoxide aggregates by the phosphazene base Bu t P 4 , and chain lenght effects. It depends on reaction temperature, concentration of the phosphazene base Bu t P 4 , as well as the structure of the initiator.

The influence of different confinements active during crystallization within polybutadiene-block-polyisoprene-block-poly(ethylene oxide) (PB-b-PI-b-PEO) and the corresponding hydrogenated polyethylene-block-poly(ethylene-alt-propylene)-block-poly(ethylene oxide) (PE-b-PEP-b-PEO) triblock copolymers on the self-nucleation behavior of the crystallizable PEO and PE blocks is investigated by means of differential scanning calorimetry (DSC). In triblock copolymers with PEO contents ≤ 20 wt.-% crystallizationof PEO is confined within small isolated microdomains (spheres or cylinders), and PEO crystallization takes place exclusively at high supercoolings. Self-nucleation experiments reveal an anomalous behavior in comparison to the classical self-nucleation behavior found in semicrystalline homopolymers. In these systems, domain II (exclusive self-nucleation domain) vanishes, and self-nucleation can only take place at lower temperatures in domain III SA , when annealing is already active. The self-nucleation behavior of the PE blocks is significantly different compared with that of the PEO blocks. Regardless of the low PE content (10-25 wt.-%) on the investigated PE-b-PEP-b-PEO triblock copolymers a classical self-nucleation behavior is observed, i.e., all three self-nucleation domains, usually present in crystallizable homopolymers, can be located. This is a direct result of the small segmental interaction parameter of the PEP and PE segments in the mel. As a consequence, crystallization of PE occurs without confinement from a homogeneous mixture of PE and PEP segments. Self-nucleation regimes of a block copolymer showing confined crystallization by means of DSC.

We have been able to prepare a molecular complex between the poly(ethylene oxide) block of a poly(ethylene)-b-poly(ethylene-alt-propylene)-b-poly(ethylene oxide) triblock copolymer and p-nitrophenol (PNP). The composition of the copolymer employed was: 24% PE, 57% PEP and 19% PEO in weight percent. The pure copolymer exhibited a nonconventional thermal behavior since the PEO block displayed a fractionated crystallization process during cooling. The PEO block /PNP complex did not show any apparent crystallization during cooling, instead cold crystallization during heating was observed and an approximately 30 °C increase in melting point as compared to the neat PEO block within the copolymer. This caused an overlap in the melting regions of the PE block and the PEO block/PNP complex. The self-nucleation of the PE-b-PEP-b-PEO/PNP complex is very different from that of the neat triblock copolymer. An increased capacity for self-nucleation of the PEO block was produced by the complexation with PNP and therefore the three self-nucleation domains were clearly encountered for both the PE block and for the PEO block/PNP complex. Self-nucleation was able to show that the two crystallizable blocks can be self-nucleated and annealed in an independent way, thereby ascertaining the presence of separate crystalline regions in the triblock copolymer. Through the use of PNP, both the crystallinity and the melting point of the PE-b-PEP-b-PEO block copolymer employed here can be substantially increased. Similar results were obtained by complexation of the same ABC triblock copolymer with resorcinol.

Nature is an intriguing inspiration for designing a myriad of functional materials. However, artificial mimicking of bioinspired structures usually requires different specialized procedures and setups. In this study, a new upscalable concept is presented that allows to produce two bioinspired, bicomponent fiber morphologies (side-by-side and coaxial bead-on-string) using the same electrospinning setup, just by changing the employed spinning solvent. The generated fiber morphologies are highly attractive for thermoresponsive actuation and water harvesting. Another challenge solved in this work is the compositional characterization of complex fiber morphologies. Raman imaging and atomic force microscopy is introduced as a powerful method for the unambiguous characterization of complex bicomponent fiber morphologies. The work opens the way for the construction of heterostructured fiber morphologies based on different polymers combinations, offering high potential for applications as actuators, smart textiles, water management, drug release, and catalysis.

Three approaches to the synthesis of L-leucine selectively labelled with carbon-13 or deuterium in either diastereotopic methyl group as well as at C-3 and C-4 are described. In all three methods the stereogenic centre at C-2 was created with total stereocontrol via a one-pot, two-enzyme catalysed procedure involving hydrolysis and reductive amination of a 2-keto ester. However, the approaches vary in the synthesis of the isotopically labelled 2-keto esters and in the production of the stereogenic centre at C-4 which was achieved either via alkylation of a propionylated Evans’ auxiliary with labelled iodomethane or by the diastereoselective conjugate addition of a labelled organocopper reagent to crotonate tethered to a chiral sultam. The latter approach proved most efficient and using the (1R,2S,3R)-3-[N-phenylsulfonyl-N-(3,5-dimethyldiphenyl)aminobornan-2-ol ester 27, [5-13C]-L-leucine was prepared with >98% de at C-4 and in 49% overall yield from the first labelled intermediate 28.