Synthesis of novel boronic acid-decorated poly(2-oxazoline)s showing triple-stimuli responsive behavior

Boronic acid-functionalized (co)polymers have gained increasing attention in the field of responsive polymers and polymeric materials due to their unique characteristics and responsiveness towards both changes in pH and sugar concentrations. This makes these (co)polymers excellently suited for various applications including responsive membranes, drug delivery applications and sensor materials. Unfortunately, boronic acid-based polymer research is also notorious for its challenging monomer synthesis and polymerization and its overall difficult polymer purification and manipulation. In light of this, many research groups have focused their attention on the optimization of various polymerization techniques in order to expand the field of BA-research including previously unexplored monomers and polymerization techniques. In this paper, a new post-polymerization modification methodology was developed allowing for the synthesis of novel boronic acid-decorated poly(2-alkyl-2-oxazoline) (PAOx) copolymers, utilizing the recently published PAOx methyl ester reaction platform. The developed synthetic pathway provides a straightforward method for the introduction of pH- and glucose-responsiveness, adding this to the already wide variety of possible responsive PAOx-based systems. The synthesized BA-decorated PAOx are based on the thermoresponsive poly(2-n-propyl-2-oxazoline) (PnPropOx). This introduces a pH and glucose dependence on both cloud and clearance point temperatures of the copolymer in aqueous and pH-buffered conditions, yielding a triply-responsive (co)polymer that highlights the wide variety of obtainable properties using this pathway

Achievements and state of the art of hydrogen fuelled IC engines after twenty years of research at Ghent University

Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.Hydrogen could be “the” fuel for the future, not only for fuel cells but certainly for internal combustion engines. The research on hydrogen started at Ghent University in 1990 with the adaptation of a Valmet diesel engine to hydrogen operation (atmospheric, carbureted version) to prove the capability of hydrogen as a fuel for IC engines. Since then several engines were modified for hydrogen use with the state of the art technologies (sequential injection, electronic management units). With European (Craft, Brite) and Belgian grants three buses demonstrated on several levels the application of hydrogen IC engines. At the moment the laboratory test proves an operation with a power output higher than the gasoline engine, with an equal efficiency of the diesel engine and with very low emissions (NOx less than 100 ppm). The interests of the research group of Ghent University was not only for the experimental work, but also the combustion process is simulated (GUEST code). The estimated formula of the laminar flame speed of hydrogen by Verhelst is worldwide used in other research studies. At the moment a doctoral study examines the heat transfer in hydrogen engines, which is so different from the already not very accurate heat transfer models in gasoline and diesel engines. In our laboratory tests, the hydrogen engine is ready for mass production (backfire safe, high power output, high efficiency, very low emissions). But storage on the vehicle recently and infrastructure of the fuel delivery are the bottle-necks for a real implementation of the hydrogen economy. From hydrogen, methanol can be produced on a sustainable way. Methanol is a liquid (no storage problem on het vehicle) and with minor modifications the same infrastructure can be used as for gasoline. Methanol has very good engine characteristics. Will methanol based on hydrogen be then “the” fuel of the future?mp201

Development and validation of A quasi-dimensional model for (M)Ethanol-Fuelled SI engines

RESEARCH OBJECTIVE - The use of methanol and ethanol in spark-ignition engines forms an interesting approach to decarbonizing transport and securing domestic energy supply. Experimental work has produced promising results, however, the full potential of light alcohols in modern engine technology remains to be explored. Today, this can be addressed at low cost using system simulations of the whole engine, provided that the employed models account for the effect of the fuel on engine operation. The goal of current work is to develop an engine cycle model that can accurately predict performance, efficiency, pollutant emissions and knock onset in state-of-the-art neat alcohol engines. METHODOLOGY - Two-zone thermodynamic engine modeling, in combination with 1D gas dynamics, is put forward as a useful tool for cheap and fast optimization of engines. Typically, this model class derives the mass burning rate of fuel from turbulent combustion models. A fundamental building block of turbulent combustion models is an expression for the laminar burning velocity of the fuel-air-residuals mixture at instantaneous cylinder pressure and temperature. This physicochemical property basically groups the contribution of the chemical reactions (of the fuel) to combustion. Consequently, an important part of our study consisted of calculating (using chemical kinetics) and measuring the laminar burning velocity of methanol and ethanol at engine-like conditions. In order to validate the developed engine model, its predictions were compared against a database of experimental results obtained on three different flex-fuel and dedicated alcohol engines. RESULTS - Comparison of the experimental and simulated cylinder, intake and exhaust pressure traces confirmed the predictive power of our engine model for methanol-fuelled engines. A wide variety of engine operating points were accurately reproduced thanks to a new laminar burning velocity correlation, which correctly accounts for changes in pressure, temperature, mixture richness and residual ratio. The Flame Closure Model of Zimont-Lipatnikov emerged as the most widely applicable model from a comparison of several turbulent combustion models. With regard to the gas dynamics it proved necessary to include a fuel puddling submodel to take the cooling effect due to alcohol injection into consideration. LIMITATIONS - The developed model was successfully validated for normal combustion in port-injected neat methanol engines. The validation of the routines for ethanol combustion and engines with direct injection is part of ongoing work. Now that normal combustion can be accurately simulated, further work will look at the prediction of pollutant emissions and knock onset in these engines. NOVELTY - This paper presents the first recent attempt to model the application of neat alcohols in modern and anticipated future engine technologies. Compared to previous work the effects of in-cylinder and mixture conditions on the combustion are more accurately predicted thanks to the inclusion of a new and widely validated laminar burning velocity correlation. In contrast to other studies, the current experimental database also includes measurements on turbocharged, high compression ratio engines with elevated amounts of EGR, which is representative of future dedicated alcohol engines. CONCLUSIONS - The current work focused on adapting the various submodels of quasi-dimensional engine codes to the properties of light alcohols. The developed simulation tools can be used with confidence to optimize current and future engines running on neat methanol and ethanol. This work also forms the starting point for an extension of the modelling concepts to alcohol-gasoline blends, which hold more industrial relevance

Theoretical study of the electronic spectra of small molecules that incorporate analogues of the copper-cysteine bond

The copper-sulphur bond which binds cysteinate to the metal centre is a key factor in the spectroscopy of blue copper proteins. We present theoretical calculations describing the electronically excited states of small molecules, including CuSH, CuSCH_3, (CH_3)_2SCuSH, (imidazole)-CuSH and (imidazole)_2-CuSH, derived from the active site of blue copper proteins that contain the copper-sulphur bond in order to identify small molecular systems that have electronic structure that is analogous to the active site of the proteins. Both neutral and cationic forms are studied, since these represent the reduced and oxidised forms of the protein, respectively. For CuSH and CuSH^+, excitation energies from time-dependent density functional theory with the B97-1 exchange-correlation functional agree well with the available experimental data and multireference configuration interaction calculations. For the positive ions, the singly occupied molecular orbital is formed from an antibonding combination of a 3d orbital on copper and a 3pπ orbital on sulphur, which is analogous to the protein. This leads several of the molecules to have qualitatively similar electronic spectra to the proteins. For the neutral molecules, changes in the nature of the low lying virtual orbitals leads the predicted electronic spectra to vary substantially between the different molecules. In particular, addition of a ligand bonded directly to copper results in the low-lying excited states observed in CuSH and CuSCH_33 to be absent or shifted to higher energies

Theoretical investigation of the electronic structure of Fe(II) complexes at spin-state transitions

The electronic structure relevant to low spin (LS)high spin (HS) transitions in Fe(II) coordination compounds with a FeN6 core are studied. The selected [Fe(tz)6]2+(1) (tz=1H-tetrazole), [Fe(bipy)3]2+(2) (bipy=2,2’-bipyridine) and [Fe(terpy)2]2+ (3) (terpy=2,2’:6’,2’’-terpyridine) complexes have been actively studied experimentally, and with their respective mono-, bi-, and tridentate ligands, they constitute a comprehensive set for theoretical case studies. The methods in this work include density functional theory (DFT), time-dependent DFT (TD-DFT) and multiconfigurational second order perturbation theory (CASPT2). We determine the structural parameters as well as the energy splitting of the LS-HS states (ΔEHL) applying the above methods, and comparing their performance. We also determine the potential energy curves representing the ground and low-energy excited singlet, triplet, and quintet d6 states along the mode(s) that connect the LS and HS states. The results indicate that while DFT is well suited for the prediction of structural parameters, an accurate multiconfigurational approach is essential for the quantitative determination of ΔEHL. In addition, a good qualitative agreement is found between the TD-DFT and CASPT2 potential energy curves. Although the TD-DFT results might differ in some respect (in our case, we found a discrepancy at the triplet states), our results suggest that this approach, with due care, is very promising as an alternative for the very expensive CASPT2 method. Finally, the two dimensional (2D) potential energy surfaces above the plane spanned by the two relevant configuration coordinates in [Fe(terpy)2]2+ were computed both at the DFT and CASPT2 levels. These 2D surfaces indicate that the singlet-triplet and triplet-quintet states are separated along different coordinates, i.e. different vibration modes. Our results confirm that in contrast to the case of complexes with mono- and bidentate ligands, the singlet-quintet transitions in [Fe(terpy)2]2+ cannot be described using a single configuration coordinate

Catalytic Cycle of Multicopper Oxidases Studied by Combined Quantum- and Molecular-Mechanical Free-Energy Perturbation Methods

We have used combined quantum mechanical and molecular mechanical free-energy perturbation methods in combination with explicit solvent simulations to study the reaction mechanism of the multicopper oxidases, in particular the regeneration of the reduced state from the native intermediate. For 52 putative states of the trinuclear copper cluster, differing in the oxidation states of the copper ions and the protonation states of water- and O2-derived ligands, we have studied redox potentials, acidity constants, isomerisation reactions, as well as water- and O2 binding reactions. Thereby, we can propose a full reaction mechanism of the multicopper oxidases with atomic detail. We also show that the two copper sites in the protein communicate so that redox potentials and acidity constants of one site are affected by up to 0.2 V or 3 pKa units by a change in the oxidation state of the other site