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Pasel J.,Jülich Research Center | Wang Y.,Jülich Research Center | Hurter S.,Jülich Research Center | Dahl R.,Jülich Research Center | And 3 more authors.
Journal of Membrane Science | Year: 2012

This paper investigates pervaporation, a membrane separation process for the removal of sulfur-containing components from jet fuel. To this end, one type of commercial membrane from PolyAn GmbH was applied. The influence of the crucial reaction parameters of the pervaporation process, such as feed temperature, permeate pressure, and permeate temperature, on the characteristic pervaporation measures such as permeate flux and enrichment factor was tested experimentally. Fuels with different sulfur mass fractions were applied and the long-term stability of the membranes used was studied. Different spectroscopic methods were applied to investigate correlations between membrane performance and material properties of the membrane. It was found that an increased feed temperature had a positive effect on the permeate flux while it had a negative effect on the enrichment factor. At 100°C, the permeate flux amounted to 5.44kg/(hm 2), while it was only 1.16kg/(hm 2) at a feed temperature of 80°C. At a feed temperature of 80°C, the enrichment factor was 0.47, while it amounted to 0.64 at a feed temperature of 100°C. In the case of the permeate pressure, the trends were also antagonistic. Low permeate pressure enhanced the permeate flux but deteriorated the enrichment factor. At a value of 20mbar, the permeate flux amounted to 5.44kg/(hm 2), while it was only 0.16kg/(hm 2) at 100mbar. The enrichment factor was 0.64 at 20mbar and decreased to 0.35 at 100mbar. Different permeate temperatures and sulfur mass proportions had only a minor effect on the permeate flux and the enrichment factor. Experiments on the long-term stability of the membranes used showed that fortunately the pervaporation process could be run for more than 500h using membranes from PolyAn GmbH while still showing a measurable permeate flux and a remarkable reduction of the sulfur mass fraction in the permeate. However, a significant deactivation with time on stream was observed. The permeate flux continuously decreased from 3.5kg/(hm 2) to 0.5kg/(hm 2) after 532h of time on stream. The enrichment factor increased from 0.5 to 0.6. Long-term experiments with pretreated membranes revealed that interaction between the hydrocarbon matrix in kerosene Jet A-1 and the membrane material itself was not responsible for the observed degradation of performance. Spectroscopic investigations were used to show that the reduction of the permeate flux was probably caused by an irreversible inclusion of polar - mostly aromatic - molecules in the polymeric separation layer of the membrane. The probable influence of unknown additives on the permeate flux could not be proven but should be considered. No degradation of the membrane material itself was found. © 2011 Elsevier B.V.


Dimroth J.,TU Berlin | Dimroth J.,PolyAn GmbH | Keilitz J.,Free University of Berlin | Schedler U.,PolyAn GmbH | And 2 more authors.
Advanced Synthesis and Catalysis | Year: 2010

Catalyst immobilization through covalent attachment onto a support is one strategy to provide recyclable systems. Here, soluble and surface-functionalized solid polymers were used as supports for a modified tethered rhodium(III)-p-toluenesulfonyl-1,2-diphenylethylenediamine [Rh(III)-TsDPEN] complex. The supported catalysts were applied to the asymmetric transfer hydrogenation of phenyl ketones in aqueous solution of sodium formate. High ee values (up to 99%) and good activities were achieved. It was discovered that the solid polymer-supported catalyst could be recycled at least four times without a significant decrease of the activity when a mixture of sodium formate and formic acid was used as the hydrogen source. This catalytic system provides a promising approach towards an ecologically and economically rational production of enantioenriched building blocks. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Dimroth J.,TU Berlin | Schedler U.,PolyAn GmbH | Keilitz J.,Free University of Berlin | Haag R.,Free University of Berlin | Schomacker R.,TU Berlin
Advanced Synthesis and Catalysis | Year: 2011

Heterogenization is a powerful approach for the generation of easily recyclable catalysts. In this study, a modified tethered rhodium(III)- p-toluenesulfonyl-1,2-diphenylethylenediamine (Rh-TsDPEN) complex immobilized on polymeric supports was applied to kinetic and up-scaling experiments on the asymmetric transfer hydrogenation of acetophenone in water. Study of the catalyst has helped in understanding some aspects of its operating mode. The results indicate that, in the investigated range, a simple second-order model describes the enantioselective conversion of acetophenone to phenylethanol. Optimal reaction conditions were determined, and particularly the solution pH was found to play a decisive role for the activity and reusability of the catalyst. The good performance under optimized conditions emphasizes the practical usefulness of this recyclable catalytic system for environmentally benign asymmetric transfer hydrogenation processes. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Dietrich P.M.,BAM Federal Institute of Materials Research and Testing | Hennig A.,BAM Federal Institute of Materials Research and Testing | Holzweber M.,BAM Federal Institute of Materials Research and Testing | Thiele T.,PolyAn GmbH | And 5 more authors.
Journal of Physical Chemistry C | Year: 2014

We report a surface analytical study of poly(methyl methacrylate) (PMMA) microparticles (beads) with a grafted shell of poly(acrylic acid) (PAA) with thicknesses up to 4 nm using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and near-edge X-ray adsorption fine structure (NEXAFS) spectroscopy. These polymer microparticles were analyzed before and after reaction of the surface carboxyl (CO2H) groups with 2,2,2-trifluoroethylamine (TFEA) to gain a better understanding of methods with use of covalently bound probe molecules for surface group analysis. The results obtained with chemical derivatization XPS using TFEA are discussed in terms of surface quantification of reactive CO2H groups on these PAA-coated microparticles. A labeling yield of about 50% was found for TFEA-derivatized particles with amounts of surface-grafted CO2H groups of 99 μmol/g or more, which is consistent with predicted reaction yields for homogeneously dispersed PAA hydrogels. © 2014 American Chemical Society.


Rodiger S.,TU Brandenburg | Liebsch C.,TU Brandenburg | Schmidt C.,TU Brandenburg | Lehmann W.,Attomol GmbH | And 3 more authors.
Microchimica Acta | Year: 2014

Microbead-based technologies represent elegant and versatile approaches for highly parallelized quantitative multiparameter assays. They also form the basis of various techniques for detection and quantification of nucleic acids and proteins. Nucleic acid-based methods include hybridization assays, solid-phase PCR, sequencing, and trapping assays. Microbead assays have been improved in the past decades and are now important tools in routine and point-of-care diagnostics as well as in life science. Its advances include low costs, low workload, high speed and high-throughput automation. The potential of microbead-based assays therefore is apparent, and commercial applications can be found in the detection and discrimination of single nucleotide polymorphism, of pathogens, and in trapping assays. This review provides an overview on microbead-based platforms for biosensing with a main focus on nucleic acid detection (including amplification strategies and on selected probe systems using fluorescent labeling). Specific sections cover chemical properties of microbeads, the coupling of targets onto solid surfaces, microbead probe systems (mainly oligonucleotide probes), microbead detection schemes (with subsections on suspension arrays, microfluidic devices, and immobilized microbeads), quantification of nucleic acids, PCR in solution and the detection of amplicons, and methods for solid-phase amplification. We discuss selected trends such as microbead-coupled amplification, heterogeneous and homogenous DNA hybridization assays, real-time assays, melting curve analysis, and digital microbead assays. We finally discuss the relevance and trends of the methods in terms of high-level multiplexed analysis and their potential in diagnosis and personalized medicine. Contains 211 references. [Figure not available: see fulltext.] © 2014 Springer-Verlag Wien.


Hennig A.,BAM Federal Institute of Materials Research and Testing | Borcherding H.,PolyAn GmbH | Jaeger C.,BAM Federal Institute of Materials Research and Testing | Hatami S.,BAM Federal Institute of Materials Research and Testing | And 6 more authors.
Journal of the American Chemical Society | Year: 2012

The amount of grafted poly(acrylic acid) on poly(methyl methacrylate) micro- and nanoparticles was quantified by conductometry, 13C solid-state NMR, fluorophore labeling, a supramolecular assay based on high-affinity binding of cucurbit[7]uril, and two colorimetric assays based on toluidine blue and nickel complexation by pyrocatechol violet. The methods were thoroughly validated and compared with respect to reproducibility, sensitivity, and ease of use. The results demonstrate that only a small but constant fraction of the surface functional groups is accessible to covalent surface derivatization independently of the total number of surface functional groups, and different contributing factors are discussed that determine the number of probe molecules which can be bound to the polymer surface. The fluorophore labeling approach was modified to exclude artifacts due to fluorescence quenching, but absolute quantum yield measurements still indicate a major uncertainty in routine fluorescence-based surface group quantifications, which is directly relevant for biochemical assays and medical diagnostics. Comparison with results from protein labeling with streptavidin suggests a porous network of poly(acrylic acid) chains on the particle surface, which allows diffusion of small molecules (cutoff between 1.6 and 6.5 nm) into the network. © 2012 American Chemical Society.


Heise C.,PolyAn GmbH | Ehrentreich-Forster E.,Fraunhofer Institute for Biomedical Engineering | Bier F.F.,Fraunhofer Institute for Biomedical Engineering
Journal of Chemical Technology and Biotechnology | Year: 2012

BACKGROUND: The fluorescence dye 5-dimethylamino-1-naphthalenesulfonyl chloride (Dansyl chloride) is commonly used for labeling the N-terminus of proteins and peptides. Apart from the fluorescence, the -SO 2-NH-bonds formed are susceptible to photolytic cleavage and will subsequently restore free amines. Consequently, Dansyl amides could act as a fluorescent photoprotecting group with novel application in solid phase synthesis or in microarray technologies. RESULTS: Commercial microscope glass slides were silanized with (3-aminopropyl) triethoxysilane, exposed amines were activated with 1,4-phenylene diisothiocyanate and subsequently reacted with dansylated polyethylene imine (PEI). The resulting fluorescence of the surface was determined and used as a measure of the homogeneity of the introduced functional groups. Using a mask, Dansyl-PEI modified slides were locally exposed to photolytic cleavage within irradiation energy of 100 J cm -2. Inscribed structures would be easily recognized due to their loss of fluorescence. The restored amines in deprotected areas were reacted with phosphorylated capture oligonucleotides followed by hybridization with complementary Cy5-labeled targets. CONCLUSIONS: Capture probes immobilized precisely in structures exposed to UV-light while non-irradiated areas remained blocked. Such pre-structured surfaces allow the production of highly reproducible microarrays without any specific problems of spotting imperfections. Gridding and segmentation of the determined sample allocation facilitate spot finding and spot analysis. © 2012 Society of Chemical Industry.


Hennig A.,BAM Federal Institute of Materials Research and Testing | Hoffmann A.,BAM Federal Institute of Materials Research and Testing | Borcherding H.,PolyAn GmbH | Thiele T.,PolyAn GmbH | And 2 more authors.
Chemical Communications | Year: 2011

We introduce a method to determine the number of accessible functional groups on a polymer microsphere surface based on the interaction between the macrocyclic host cucurbit[7]uril (CB7) and a guest reacted to the microsphere surface. After centrifugation, CB7 in the supernatant is quantified by addition of a fluorescent dye. The difference between added and detected CB7 affords the number of accessible surface functional groups. © 2011 The Royal Society of Chemistry.


Hennig A.,BAM Federal Institute of Materials Research and Testing | Hoffmann A.,BAM Federal Institute of Materials Research and Testing | Borcherding H.,PolyAn GmbH | Thiele T.,PolyAn GmbH | And 2 more authors.
Analytical Chemistry | Year: 2011

We present a novel, simple, and fast colorimetric method to quantify the total number of carboxy groups on polymer microparticle and nanoparticle surfaces. This method exploits that small divalent transition metal cations (M2+ = Ni2+, Co2+, Cd2+) are efficiently bound to these surface functional groups, which allows their extraction by a single centrifugation step. Remaining M2+ in the supernatant is subsequently quantified spectrophotometrically after addition of the metal ion indicator pyrocatechol violet, for which Ni2+ was identified to be the most suitable transition metal cation. We demonstrate that the difference between added and detected M2+ is nicely correlated to the number of surface carboxy groups as determined by conductometry, thereby affording a validated measure for the trueness of this procedure. The variation coefficient of ∼5% found in reproducibility studies underlines the potential of this novel method that can find conceivable applications for the characterization of different types of poly(carboxylic acid)-functionalized materials, e.g., for quality control by manufacturers of such materials. © 2011 American Chemical Society.


Heise C.,PolyAn GmbH | Schedler U.,PolyAn GmbH | Wettmarshausen S.,BAM Federal Institute of Materials Research and Testing | Friedrich J.F.,BAM Federal Institute of Materials Research and Testing
Journal of Applied Polymer Science | Year: 2014

Activators regenerated by electron transfer-atom radical transfer polymerization (ATRP) as a controlled living polymerization are distinguished by their acceptance of small amounts of transition-metal complexes and oxygen and by their tolerance of reducing agents at a high concentration. The precondition of all ATRP applications is the use of homolytic or heterolytic cleavable halides as a dormant species; this allows the propagation of monomer chains. Hence, alkyl bromides are slightly cleavable and are the preferred initiators for ATRP. The bromination of polymer slides used as macroinitiators was carried out under gentle bromoform plasma conditions. This led to an oxidation-resistant stable bromine layer. More than 20 bromines per 100 carbons on the polymer scaffold were permanently bound to the substrate after plasma treatment. The resulting amounts of secondary and tertiary bromines on the polymer scaffold exhibited a suitable macroinitiator concentration for the surface-initiated polymerization of methyl methacrylate and glycidyl methacrylate. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40662. Copyright © 2014 Wiley Periodicals, Inc.

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