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10-Undecenal, derived by pyrolysis and reduction from castor oil, was almost quantitatively transformed into the corresponding aldol condensation product under basic conditions. This alpha,omega-diene monomer was polymerized using acyclic diene metathesis (ADMET) polymerization. In a catalyst screening, four of nine different ruthenium-based metathesis catalysts showed good reactivity under neat conditions at 80 degrees C in the presence of 1,4-benzoquinone and polymers with molecular weights up to 11 kDa were formed. Furthermore, the (1)H NMR spectra showed that the metathesis catalysts tolerate the alpha,beta-unsaturated aldehyde function and due to the addition of benzoquinone, the degree of double bond isomerization was low. Further experiments investigating reduced catalyst amounts (down to 0.2 mol%) and the temperature dependence of these ADMET polymerizations gave also satisfying results for the formation of poly-alpha,beta-unsaturated aldehydes. Moreover, ADMET polymerizations with different amounts of methyl 10-undecenoate as chain-stopper were performed and the integrals of the corresponding (1)H NMR spectra allowed the determination of an absolute degree of polymerization. Finally, a reduction of a poly-alpha,beta-unsaturated aldehyde with sodium borohydride was accomplished. The resulting poly-(allyl alcohol) could be a useful compound in the generation of polymer networks like polyesters, polyurethanes, and polycarbonates and thus be of high interest in materials research.
Functional hybrid materials on the basis of inorganic hosts and ionic liquids (ILs) as guests hold promise for a virtually unlimited number of applications. In particular, the interaction and the combination of properties of a defined inorganic matrix and a specific IL could lead to synergistic effects in property selection and tuning. Such hybrid materials, generally termed ionogels, are thus an emerging topic in hybrid materials research. The current article addresses some of the recent developments and focuses on the question why silica is currently the dominating matrix used for (inorganic) ionogel fabrication. In comparison to silica, matrix materials such as layered simple hydroxides, layered double hydroxides, clay-type substances, magnetic or catalytically active solids, and many other compounds could be much more interesting because they themselves may carry useful functionalities, which could also be exploited for multifunctional hybrid materials synthesis. The current article combines experimental results with some arguments as to how new, advanced functional hybrid materials can be generated and which obstacles will need to be overcome to successfully achieve the synthesis of a desired target material.
The synthesis of Co-NPs and Mn-NPs by microwave-induced decomposition of the metal carbonyls Co-2(CO)(8) and Mn-2(CO)(10), respectively, yields smaller and better separated particles in the functionalized IL 1-methyl-3-(3-carboxyethyl)-imidazolium tetrafluoroborate [EmimCO(2)H][BF4] (1.6 +/- 0.3 nm and 4.3 +/- 1.0 nm, respectively) than in the non-functionalized IL 1-n-butyl-3-methylimidazolium tetrafluoroborate [Bmim][BF4]. The particles are stable in the absence of capping ligands (surfactants) for more than six months although some variation in particle size could be observed by TEM.
Gold(III) bromide is a suitable catalyst for the stereoselective cyclization of 2-C-malonyl carbohydrates to the anomeric center under retention of one ester group. Reopening of the lactones with alcohols in the presence of TMSOTf affords allyl, propargyl and benzyl glycosides with high alpha-selectivity.
Novel fluorescent nanosensors, based on a naphthyridine receptor, have been developed for the detection of guanosine nucleotides, and both their sensitivity and selectivity to various nucleotides were evaluated. The nanosensors were constructed from polystyrene nanoparticles functionalized by (N-(7-((3-aminophenyl) ethynyl)-1,8-naphthyridin- 2-yl) acetamide) via carbodiimide ester activation. We show that this naphthyridine nanosensor binds guanosine nucleotides preferentially over adenine, cytosine, and thymidine nucleotides. Upon interaction with nucleotides, the fluorescence of the nanosensor is gradually quenched yielding Stern-Volmer constants in the range of 2.1 to 35.9mM(-1). For all the studied quenchers, limits of detection (LOD) and tolerance levels for the nanosensors were also determined. The lowest (3 sigma) LOD was found for guanosine 3',5'-cyclic monophosphate (cGMP) and it was as low as 150 ng/ml. In addition, we demonstrated that the spatial arrangement of bound analytes on the nanosensors' surfaces is what is responsible for their selectivity to different guanosine nucleotides. We found a correlation between the changes of the fluorescence signal and the number of phosphate groups of a nucleotide. Results of molecular modeling and zeta-potential measurements confirm that the arrangement of analytes on the surface provides for the selectivity of the nanosensors. These fluorescent nanosensors have the potential to be applied in multi-analyte, array-based detection platforms, as well as in multiplexed microfluidic systems.
Point-of-care testing (POCT) systems which allow for a sensitive, quantitative detection of protein markers are extremely useful for the early detection and therapy progress monitoring of cancer. However, currently commercially available POCT devices are mainly limited to the qualitative detection of protein markers. In this study we demonstrate the successive miniaturization of a sensitive and fast assay for the quantitative detection of prostate-specific antigen (PSA) using a well established and clinically approved homogeneous time-resolved fluoroimmunoassay technology (TRACE (R)) on a commercial plate-reader system (KRYPTOR (R)). Regarding the initial requirements for the development of POCT devices we applied a 30-fold assay volume reduction (150 mu L to 5 mu L) to achieve a reasonable lab-on-a-chip volume and a 24-fold and 120-fold excitation pulse energy reduction to achieve reasonable pulse energies for low-cost miniature excitation sources. Due to highly efficient optimization of key POCT parameters our miniaturized PSA assay achieved a 30% increased sensitivity and a 2-fold improved limit of detection compared to the standard plate-reader method. Our results demonstrate the successful implementation of key parameters for a significant miniaturization and for cost reduction in the clinically approved KRYPTOR (R) platform for protein detection. The technological alterations required are easy-to-implement and can be immediately adapted for more than 30 diagnostic protein markers already available for the KRYPTOR (R) platform. These features strongly recommend our assay format to be utilized in innovative, sensitive, quantitative POCT of protein markers.
Examining the UV-vis absorption of RAFT chain transfer agents and their use for polymer analysis
(2011)
The absorption characteristics of a large set of thiocarbonyl based chain transfer agents (CTAs) were studied by UV-vis spectroscopy in order to identify appropriate conditions for exploiting their absorbance bands in end-group analysis of polymers prepared by reversible addition-fragmentation chain transfer (RAFT) polymerisation. Substitution pattern and solvent polarity were found to affect notably the wavelengths and intensities of the pi-pi*- and n-pi*-transition of the thiocarbonyl bond of dithioester and trithiocarbonate RAFT agents. Therefore, it is advisable to refer in end group analysis to the spectral parameters of low molar mass analogues of the active polymer chain ends, rather than to rely on the specific RAFT agent engaged in the polymerisation. When using appropriate conditions, the quantification of the thiocarbonyl end-groups via the pi-pi* band of the thiocarbonyl moiety around 300-310 nm allows a facile, sensitive and surprisingly precise estimation of the number average molar mass of the polymers produced, without the need of particular end group labels. Moreover, when additional methods for absolute molar mass determination can be applied, the quantification of the thiocarbonyl end-groups by UV-spectroscopy provides a good estimate of the degree of active end group for a given polymer sample.
Wave energy harvesting could be a substantial renewable energy source without impact on the global climate and ecology, yet practical attempts have struggled with the problems of wear and catastrophic failure. An innovative technology for ocean wave energy harvesting was recently proposed, based on the use of soft capacitors. This study presents a realistic theoretical and numerical model for the quantitative characterization of this harvesting method. Parameter regions with optimal behavior are found, and novel material descriptors are determined, which dramatically simplify analysis. The characteristics of currently available materials are evaluated, and found to merit a very conservative estimate of 10 years for raw material cost recovery.
Using cationic polyelectrolytes with different molecular architectures, only hyperbranched poly(ethyleneimine) with maltose shell is suited to tailor the morphological transformation of anionic vesicles into tube-like networks. The interaction features of those materials partly mimic biological features of tubular proteins in nature.