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wszystkich: 2102
wybranych: 1919
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wyświetlamy 1000 najlepszych wyników Pomoc
Wyniki wyszukiwania dla: emerging organic pollutants
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Amine-Catalyzed Direct Aldol Reactions of Hydroxy- and Dihydroxyacetone: Biomimetic Synthesis of Carbohydrates
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Bypassing the stereoselectivity issue: transformations of Kinugasa adducts from chiral alkynes and non-chiral acyclic nitrones
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A Unique and Stable Polyproline I Helix Sorted out from Conformational Equilibrium by Solvent Polarity
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Practical Method for the Absolute Configuration Assignment of tert/tert 1,2-Diols Using Their Complexes with Mo2(OAc)4
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The Oxolane Ring Opening of Some Muramic Acid Derivatives Under Acidic Conditions
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Chemical Reduction of 2,4,6-Tricyano-1,3,5-triazine and 1,3,5-Tricyanobenzene. Formation of Novel 4,4‘,6,6‘-Tetracyano-2,2‘-bitriazine and Its Radical Anion
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Toward an Understanding of the Chemiluminescence Accompanying the Reaction of 9-Carboxy-10-methylacridinium Phenyl Ester with Hydrogen Peroxide
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Application of Monoferrocenylsumanenes Derived from Sonogashira Cross-Coupling or Click Chemistry Reactions in Highly Sensitive and Selective Cesium Cation Electrochemical Sensors
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Correction to Aromatic Dendrimers Bearing 2,4,6-Triphenyl-1,3,5-triazine Cores and Their Photocatalytic Performance
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Supramolecular Interactions between β-Cyclodextrin and the Nucleobase Derivatives of Ferrocene
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Aromatic Dendrimers Bearing 2,4,6-Triphenyl-1,3,5-triazine Cores and Their Photocatalytic Performance
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Pincer Complexes Based on Phosphinoaminopyridines: Synthesis, Structural Characterization and Catalytic Applications
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Influence of Carbohydrate Residues on Antibacterial Activity of Vancomycin
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Nonisothermal cure kinetics of epoxy/MnxFe3-xO4 nanocomposites
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Lower rim substituted p-tert-Butylcalix[4]arenes: Part XI. New ester derivatives of calix[4]arene, their ionophoric properties and x-ray structure studies
PublikacjaPrzedstawiono syntezę 6-ciu nowych estrowych pochodnych kaliks[4]arenuw konformacji stożkowej. Pierwsze badania kompleksowania jonów metali przeprowadzone w membranach elektrod jonoselektywnych (ISE) potwierdziły kompleksowanie jonów sodu w sposób selektywny. Zaprezentowano strukturę rentgenowską monokryształów związku 6.
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Solid phase microextraction combined with chromatography - a powerful tool for determination of warfare agents and related compounds
PublikacjaOpisano zastosowanie mikroekstrakcji do fazy stacjonarnej do izolacji wzbogacania środków bojowych i produktów ich degradacji w powietrzu, wodzie i glebie oraz próbkach bilogicznych. Na etapie oznaczeń końcowych stosuje się najczęściej chromatografię gazową. Anality można pobierać przez bezpośrednie zanurzenie włókna w próbce ciekłej i gazowej oraz w fazie nadpowierzchniowej. Stosując SPME-GC można osiągnąć niskie granice oznaczalności...
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Multispectral impedance quality testing of coil-coating system using principal component analysis
PublikacjaThe task of quality checking of the coil-coated system was undertaken using impedance spectroscopy. In order to properly characterize the system the new impedance spectrum was calculated as an averaged result of 12 experimental spectra obtained from 12 different places of the sample at the same time of immersion in 3% of NaCl. The experimental spectra were recorded for a 24-h period at 1 h intervals between starting points of each...
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Enantiomeric Resolution of N,N'-Dimethyldithiodianthranilide through Diastereomeric silver(I) complex. Chiroptical spectra, racemization barrier and molecular self-assembly
PublikacjaN,N'-dimetyloditiodiantranilid, związek o chiralności płaszczyznowej, rozdzielono na enancjomery. Optycznie czynne molekuły uzyskano w wyniku tworzenia chiralnego kompleksu N,N'-dimetyloditiodiantranilidu z solą srebrową kwasu (1S)-kamforosulfonowego. W oparciu o badania rentgenostrukturalne monokryształu uzyskanego kompleksu określono absolutną konfigurację przykoordynowanego ligandu jako (R). Enancjomery N,N'-dimetyloditiodiantranilid...
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Conformation Properties, Chiroptical Spectra, and Molecular Self-Assembly of 2,3-Piperazinodiones and Their Dithiono Analogues
PublikacjaRodzina chiralnych cyklicznych oksamidów została otrzymana przez kondensację optycznie czynnych 1,2-diamin ze szczawianem dietylu. Tionowanie produktów odczynnikiem Lawessona doprowadziło do chiralnych 2,3-dipiperazynodionów. Geometrie cząsteczkowe badano z użyciem obliczeń kwantowo-mechanicznych DFT i porównano z wynikami analizy krystalograficznej. Sześcioczłonowy pierścień heterocykliczny przyjmuje konformację półkrzesłową,...
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Determination of time dependence of coated metal electrical and electrochemical parameters during exposure using principal component analysis
PublikacjaThe use of the principal component analysis (PCA) permits the complex and quantitative analysis of the time dependence of electrical and electrochemical parameters of coated metal obtained by fitting impedance data. So far, changes in electrical and electrochemical parameters during exposure were analyzed independently. In this way, some of the information contained in the relationship between changes in parameters over time are...
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Towards β-selectivity in functional estrogen receptor antagonists
PublikacjaBased on the benzo[b]naphtho[1,2-d]furan and benzo[b]naphtho[1,2-d]thiophene frameworks, a series of ligands with different basic side chains (BSCs) has been synthesized and pharmacologically evaluated. Also, their binding modes have been modelled using docking techniques. It was found that the introduction of a BSC in these systems brings about a decrease of affinity for both estrogen receptors α and β in an in vitro competitive...
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Assessment of protective properties of rubber lining in absorbers of flue gas desulphurization systems.
PublikacjaResults of research on degradation of rubber lining which is the main protection of absorbers in flue gas desulphurization (FGD) systems were presented. The power plant where the system operated is lignite-fired. Owing to measurements using electrochemical impedance spectroscopy and gravimetric determination of water content in the lining, the areas of the system which are most exposed to degradation were shown. The results obtained...
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Synthesis and structural investigation of N-acyl selenophosphoramides
PublikacjaN-acylowane amidy kwasu O,O-neopentylidenomonoselenofosforowego, w zależności od podstawnika na atomie azotu, krystalizują jako konformery zawierające selen w pozycji ekwatorialnej bądź aksjalnej. Wyniki tych eksperymentów wyjaśniono działaniem efektu anomerycznego.
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Investigation of morphological and electrical properties of the PMMA coating upon exposure to UV irradiation based on AFM studies
PublikacjaCelem badania było określenie wpływu promieniowania ultrafioletowego na morfologię powierzchni powłoki i na jej właściwości elektryczne. Cienka powłoka z polimetakrylanu metylu została nałożona na podłoże stalowe metodą zanurzeniową. Oceny stanu przed ekspozycją UV i w jej trakcie dokonywano przy użyciu mikroskopu sił atomowych. Na obrazach AFM zaobserwowano pojawienie się mikropęknięć. Celem zweryfikowania czy wykryte nieciągłości...
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Fate of Ionic Liquids in Soils and Sediments
PublikacjaZrozumienie losu cieczy jonowych w glebach i osadach dennych jest istotnym elementem ich implementacji z zachowaniem idei zrównoważonego rozwoju. Niniejsza publikacja zawiera analizę i podsumowanie danych dotyczących oddziaływań cieczy jonowych w roztworach wodnych oraz agregacji na powierzchniach stałych. Zaobserwowano, że silnie lipofilowe ciecze jonowe zawierające długi łańcuch węglowodorowy lub duży organiczny anion wykazują...
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Properties of nano-Fe3O4 incorporated epoxy coatings from Cure Index perspective
PublikacjaThe mission of an advanced epoxy-based nanocomposite coating is to provide a given substrate with protection against an unwelcome guest; e.g. corrosive molecules/media, environmental stress, flame, thermal degradation or microorganisms. In such systems, the degree to which superior properties can be guaranteed depends on the state of network formation in the epoxy in the presence of nanoparticles. For low-filled epoxy nanocomposite coatings,...
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Cure Index demonstrates curing of epoxy composites containing silica nanoparticles of variable morphology and porosity
PublikacjaAn image was taken by Cure Index on curability of epoxy with silica nanoparticles having variable morphology and porosity. Three kinds of silica nanoparticles with non-porous curved-rod, non-porous spherical, and mesoporous spherical microstructures were synthesized and characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy (SEM) and Brunauer–Emmett–Teller analyses. Epoxy nanocomposites containing...
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Curing epoxy with electrochemically synthesized Zn Fe3-O4 magnetic nanoparticles
PublikacjaCathodic electrodeposition (CED) was applied in synthesis of undoped and zinc (Zn) doped Fe3O4 nanoparticles. Changes in the lattice structure of nanoparticles were monitored using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) supported by dispersive X-ray spectrometry (EDS), and vibrating sample magnetometry (VSM). Detailed analyses explored the formation of ZnxFe3–xO4 nanoparticles with x ≈ 0.1,...
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Curing epoxy with ethylenediaminetetraacetic acid (EDTA) surface-functionalized Co Fe3-O4 magnetic nanoparticles
PublikacjaIn this work, the bulk and surface composition of Fe3O4 supermagnetic nanoparticles were modified for efficient epoxy curing. The bare, ethylenediaminetetraacetic acid (EDTA) capped, and cobalt (Co)-doped EDTA capped Fe3O4 nanoparticles were synthesized electrochemically. The crystalline structure and phase information, surface capping, morphology and magnetization behavior of nanoparticles were studied by X-Ray diffraction (XRD),...
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Unconditionally blue: Curing epoxy with polyethylene glycol (PEG) surface-functionalized Zn Fe3-O4 magnetic nanoparticles
PublikacjaNanoparticles govern early (chemical-controlled) and late (diffusion-controlled) stages of epoxy crosslinking, respectively. Surface functionalization of nanoparticles with macromolecules was recognized as an effective route to compensate for inadequate diffusion-controlled crosslinking. However, the effect of bulk composition amended with cations having catalytic effect towards epoxy ring opening has remained hitherto undescribed....
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Degradation of protective coatings in steel chimneys of flue gas desulfurisation system
PublikacjaThis paper presents problems associated with corrosion of steel stacks and changes in philosophy of corrosion protection when implemented into flue gas desulphurization systems. In-situ tests were taken by means of electrochemical impedance spectroscopy at the stack which discharges flue gas before wet lime/limestone desulphurization. A very quick electrolyte absorption by the spherical infill vinylester coating was found using...
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An attempt to mechanistically explain the viscoelastic behavior of transparent epoxy/starch-modified ZnO nanocomposite coatings
PublikacjaThe effects of bare and starch-modified ZnO (ZnO-St) nanoparticles on viscoelastic and mechanical properties are studied by dynamic mechanical and tensile analyses. Transparent epoxy-based nanocomposite films are prepared by incorporating bare or starch-modified ZnO particles into the epoxy matrix. The results demonstrated that ZnO particles hindered the curing reactions and hence the final properties of the cured epoxy. As a result,...
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Flame retardant epoxy/halloysite nanotubes nanocomposite coatings: Exploring low-concentration threshold for flammability compared to expandable graphite as superior fire retardant
PublikacjaEpoxy nanocomposites containing halloysite nanotubes (HNTs) were developed and their low-concentration thresholds for thermal stability and flame retardancy were compared with that of epoxy system containing expandable graphite (EG), as a reference with superior flame retardancy. The effects of HNTs and EG on the peak of Heat Release Rate (pHRR), Total Heat Release (THR), and Time-To-Ignition (TTI) of the prepared samples were...
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Cure kinetics of epoxy/MWCNTs nanocomposites: Isothermal calorimetric and rheological analyses
PublikacjaA combinatorial route has been applied in cure kinetics study of epoxy nanocomposites containing multi-walled carbon nanotubes (MWCNTs) based on differential scanning calorimetry and rheokinetic analyses under isothermal conditions. Pristine and amine-modified MWCNTs bearing primary and secondary amines were used at very low concentrations (0.1 and 0.3 wt.% based on epoxy weight). Model-free and model-fitting methods were applied...
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Transparent nanocomposite coatings based on epoxy and layered double hydroxide: Nonisothermal cure kinetics and viscoelastic behavior assessments
PublikacjaLayered double hydroxide (LDH) has a particular place in clay family because of its flame retardant action. The nanoplatelet-like structure of LDH makes possible development of polymer composites with cationic or anionic nature structures in which macromolecules are positioned in between nanoplatelet galleries. In this work, neat epoxy and its transparent nanocomposite coatings with sodium dodecylbenzene sulfonate (SDBS)-modified...
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The changes of crosslink density of polyurethanes synthesised with using recycled component. Chemical structure and mechanical properties investigations.
PublikacjaThis paper aims at the utilisation of glycerolysate (Gly) obtained in polyurethane recycling process by means of crude glycerine, which has in its structure hydroxyl end groups that allow for further processing. Polyurethanes (PUs) were synthesised using prepolymer method with the mixture of neat polyol and glycerolysate, in different ratios, with 4,4-diphenylmethane diisocyanate (MDI). The prepolymer was subsequently extended...
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Curing behavior of epoxy/Fe 3 O 4 nanocomposites: A comparison between the effects of bare Fe 3 O 4 , Fe 3 O 4 /SiO 2 /chitosan and Fe 3 O 4 /SiO 2 /chitosan/imide/phenylalanine-modified nanofillers
PublikacjaIn this study, Fe3O4 magnetic nanoparticles (MNPs) were synthesized (B-MNP) and then modified with SiO2 to form Fe3O4/SiO2 core/shell MNPs. The Fe3O4/SiO2 MNPs were chemically functionalized with chitosan so as to gain Fe3O4/SiO2/Chitosan (CH-MNP). The CH-MNP was functionalized with a macromolecule containing imide and phenylalanine precursors to gain Fe3O4/SiO2/Chitosan/imide/phenylalanine based MNPs (CH-IM-MNP). The differences...
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Stereoselective Alkylation of Indole with 5-Arylidene-Meldrum’s Acids in the Presence of Organocatalysts
PublikacjaBackground: Indole motif is frequently present in biologically active compounds. Enantiomerically pure or enriched 2,2-dimethyl-5-(aryl(1H-indol-3-yl)methyl)-1,3-dioxane-4,6-diones can be considered as a convenient starting point for the synthesis of a indole ring fused with cyclic ketones with biological activity. Preparation of chiral 2,2-dimethyl-5-(aryl(1H-indol-3-yl)methyl)-1,3-dioxane- 4,6-diones requires the reaction of...
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Acid-aided epoxy-amine curing reaction as reflected in epoxy/Fe3O4 nanocomposites: Chemistry, mechanism, and fracture behavior
PublikacjaThis work seeks to answer the question whether or not the presence of acid functional groups accelerate epoxyamine curing reaction. Epoxy/Fe3O4 nanocomposite was considered as a case, where discussions are based on chemistry, mechanism behind curing reactions and fracture behavior influenced by acid assistance to crosslinking. Fe3O4 magnetic nanoparticles (MNPs) with nanosilica decorative layer (B-MNP) were synthesized and subsequently...
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5-Bromo-2′-deoxycytidine—a potential DNA photosensitizer
PublikacjaA double-stranded oligonucleotide, 80 base pairs in length, was multiply labeled with 5-bromo-2′-deoxycytidine (BrdC) using polymerase chain reaction (PCR). The modified oligonucleotide was irradiated with 300 nm photons and its damage was assayed by employing DHPLC, LC-MS and denaturing polyacrylamide gel electrophoresis (PAGE). Two types of damage were demonstrated, namely, single strand breaks (SSBs) and intrastrand cross-links...
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Curing epoxy resin with anhydride in the presence of halloysite nanotubes: the contradictory effects of filler concentration
PublikacjaEpoxy resins can be cured with a wide variety of curing agents such as amines and anhydrides, but anhydride curing would be more favorable for research purpose because of epoxy-anhydride curing taking place slowly at room temperature. Incorporation of natural nanosized minerals into epoxy is of environmental importance. Halloysite nanotubes (HNTs) display chemical properties similar to those of silica and alumina, and hydroxyl...
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Developing electrochemical measurements in order to assess anti-corrosive coatings more effectively
PublikacjaCelem pracy było sprawdzenie powtarzalności wyników uzyskanych metodą pomiaru szumu (Electrochemical Noise method - ENM) elektrochemicznego wykonanych na powłokach organicznych w konfiguracji bez połączenia z podłożem metalowym (NOCS - No Connection to the Substrate). NOCS polega na wykonaniu pomiarów na trzech teoretycznie takich samych obszarach badanego układu. W takim układzie nie jest wymagane połączenie elektryczne z metalowym...
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Stratification of nano-pigments in anti-corrosive coatings by means of magnetic field
PublikacjaThe concept of self-stratification of coatings, although attractive, causes difficulties in its practical use, especially when pigments are added to the resins. An alternative way of obtaining a multilayer structure in a single step was presented. Using the inhomogeneous magnetic field and magnetically active components of the coating, the possibility of vertically graded differentiation of the one layer properties has been verified....
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Novel application of dynamic electrochemical impedance monitoring to a cataphoretic coating process
PublikacjaThe paper presents a novel method of on-line impedance monitoring of cataphoretic coating application process. Utilization of dynamic electrochemical impedance spectroscopy (DEIS) overcame the fundamental problem connected with non-stationarity of the aforementioned coating deposition process, which eliminates classical impedance spectroscopy technique from a real-time description of cataphoresis. The paper illustrates selected examples...
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Sensing the onset of epoxy coating degradation with combined Raman spectroscopy/atomic force microscopy/electrochemical impedance spectroscopy
PublikacjaThe paper presents the results of investigation on epoxy resin durability upon 12-week exposure to UV radiation. The aim was early determination of the onset of epoxy degradation and for this purpose an epoxy film on steel substrate systems were periodically inspected using Raman spectroscopy, atomic force microscopy and electrochemical impedance spectroscopy. The behaviour of examined polymer could be divided into three periods: immunity,...
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Benzophosphol-3-yl Triflates as Precursors of 1,3-Diarylbenzophosphole Oxides
PublikacjaAsimplemethodforthesynthesisof3-arylbenzophospholeoxidesunderSuzuki−Miyauracouplingconditionshasbeenpresented.Itemploysbenzophosphol-3-yltriflatestartingmaterialswhich,priortoourwork,hadnotbeenusedforthesynthesisof3-arylbenzophospholeoxides.Thereactionsproceedover24handprovidealibraryof3-arylbenzophospholeoxides.Thesyntheticaccesstothebenzophosphol-3-yltriflateshasbeenimproved.Thepreliminaryphotophysicalpropertiesofsome3-arylbenzophospholeoxideshavebeeninvestigatedbyabsorptionandemissionmeasurements.Thetheoreticalcalculationswereperformedtoestablishstructure−propertyrelationships.
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Ring Opening of Triflates Derived from Benzophospholan-3-one Oxides by Aryl Grignard Reagents as a Route to 2‑Ethynylphenyl(diaryl)phosphine Oxides
PublikacjaA new simple method for the synthesis of 2-ethynylphenyl(diaryl)phosphine oxides via ring opening of benzophosphol-3-yl triflates has been developed. This process occurs via nucleophilic attack of a Grignard reagent at the phosphorus center, which results in ring opening and cleavage of a leaving group. The reaction proceeds under mild conditions and, within 15−60 min, leads to a library of previously unavailable 2-ethynylphenylphosphine...
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Helicity discrimination in N,N'-dibenzoyl-1,2,3,4,7,8,9,10-octahydro-1,10-phenanthrolines and their thiono- and selenocarbonyl analogues by inclusion complexation with chiral diols
PublikacjaX-ray crystallographic analysis of the title compounds revealed that they assume a folded helical con- formation of an approximate C2 symmetry in the solid state. Dithioamide, diselenoamide and monoselenoamide were resolved to enantiomers by inclusion crystallization with optically active diols (TADDOLs). The absolute configuration of the guest molecules in the complexes was assigned as P. The optical activity of the resolved compounds...
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Bio-based semi-aromatic polyesters for coating applications
PublikacjaLinear and branched bio-based semi-aromatic (co)polyesters were evaluated as resins for solvent-basedand powder coatings. Dimethyl-2,5-furandicarboxylate (DMF), 2,3-butanediol and various multifunc-tional comonomers were used to synthesize amorphous hydroxyl-end-capped (co)polyesters. The resinswere cross-linked using the -caprolactam blocked trimer of isophorone diisocyanate. Both the solvent-based and powder coatings proved to...
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Multivariate analysis of impedance data obtained for coating systems of varying thickness applied on steel
PublikacjaElectrochemical impedance spectroscopy (EIS) has proven to be a valuable test method for the electrochemical characterization of protective coatings on metals. The common way of analysis in impedance spectroscopy is to model the impedance spectrum by means of an equivalent circuit and to extract the quantity of interest using optimization techniques. A model, corresponding to the behavior of the sample under testing, is important...