Membrane gas separation technologies (air separation, hydrogen recovery from dehydrogenation processes, etc.) use traditionally the glassy polymer membranes with dominating permeability of “small” ...gas molecules. For this purposes the membranes based on the low free volume glassy polymers (e.g., polysulfone, tetrabromopolycarbonate and polyimides) are used. On the other hand, an application of membrane methods for VOCs and some toxic gas recovery from air, separation of the lower hydrocarbons containing mixtures (in petrochemistry and oil refining) needs the membranes with preferable penetration of components with relatively larger molecular sizes. In general, this kind of permeability is characterized for rubbers and for the high free volume glassy polymers. Data files accumulated (more than 1500 polymeric materials) represent the region of parameters “inside” of these “boundaries.” Two main approaches to the prediction of gas permeability of polymers are considered in this paper: (1) the statistical treatment of published transport parameters of polymers and (2) the prediction using model of ≪diffusion jump≫ with consideration of the key properties of the diffusing molecule and polymeric matrix. In the frames of (1) the paper presents N-dimensional methods of the gas permeability estimation of polymers using the correlations “selectivity/permeability.” It is found that the optimal accuracy of prediction is provided at
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The new correlations suggested demonstrate that the available free volume of polymeric matrix plays an important role in providing of rate and selectivity of gas diffusion for glassy-like polymers; the rate and selectivity of gas diffusion in rubbers is affected mainly by cohesion energy density (CED) the both polymer parameters being calculated by traditional additive group contributions technique.
Results of present study are demonstrated by calculation of expected permeability parameters in relation to lower hydrocarbons and some toxic gases for polynorbornene based polymers, PIM and PTMSP outlining potential of practical application for new membrane polymers.
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►New N-dimensional approach for prediction of gas permeability parameters of polymers ►Corrected Stuart's diameters of penetrant's molecules can be used for calculation of permanent gases, linear lower hydrocarbons and some toxic gas permeability for polymers when these data are even unavailable. ►Expected gas permeability for set of modern polymers is calculated.
This discussion comments on the approximately 20years history of writings on the prescriptive theory called Empowerment Evaluation. To do so, involves examining how “Empowerment Evaluation Theory” ...has been defined at various points of time (particularly 1996 and now in 2015). Defining a theory is different from judging the success of a theory. This latter topic has been addressed elsewhere by Michael Scriven, Michael Patton, and Brad Cousins. I am initially guided by the work of Robin Miller (2010) who has written on the issue of how to judge the success of a theory. In doing so, she provided potential standards for judging the adequacy of theories. My task is not judging the adequacy or success of the Empowerment Evaluation prescriptive theory in practice, but determining how well the theory is delineated. That is, to what extent do the writings qualify as a prescriptive theory.
Radical cyclization reactions at a peri position were used for the synthesis of polyaromatic compounds. Depending on the choice of reaction conditions and substrate, this flexible approach led to ...Bu3Sn‐substituted phenalene, benzanthrene, and olympicene derivatives. Subsequent reactions with electrophiles provided synthetic access to previously inaccessible functionalized polyaromatic compounds.
Radikalische Cyclisierungen an einer peri‐Position wurden zur Synthese polyaromatischer Verbindungen genutzt. Abhängig von der Wahl der Reaktionsbedingungen und des Substrats führt dieser flexible Ansatz zu Bu3Sn‐substituierten Phenalen‐, Benzanthren‐ und Olympicen‐Derivaten (siehe Schema). Anschließende Umsetzungen mit Elektrophilen lieferten vormals unzugängliche funktionalisierte Polyarene.
This manuscript describes the preparation of polytriazole/clay nanocomposites through in situ polymerization of PTA, using click chemistry, in the presence of a propargyl-modified clay. The clay ...layers became exfoliated and dispersed well in the PTA matrix, thereby improving the thermal and mechanical properties of the clay. This approach can be extended to combine propargyl-modified clays with other azide- and alkyne-containing polymers.
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An enantioselective Mannich‐type reaction of 3‐butynol and nitrones is described, which affords dihydrofuran‐3‐ones in good yields and with excellent enantioselectivities. The reaction is initiated ...by gold‐catalyzed alkyne oxidation and modification of the resulting gold carbene species with a tethered hydroxy group to form enolate species; the reaction terminates with an enantioselective Mannich‐type addition with the assistance of chiral phosphoric acid (CPA) and hydrogen bonding. This novel pattern of alkyne transformation involving chemical bond cleavage, and a fragment modification and reassembly process, provides an atom‐ and step‐economic method, and is the first example of cooperative asymmetric catalysis in gold‐catalyzed alkyne oxidations via an α‐oxo gold carbene route.
Golden Oldie: Ein Katalysatorsystem aus Gold(I) und chiraler Phosphorsäure (CPA) katalysiert kooperativ eine Mannich‐Reaktion. Der asymmetrische Abfang eines Goldenolat‐Zwischenprodukts, das an Alkinoxidationen beteiligt ist, erfolgt über eine α‐Oxo‐Goldcarben‐Route. Die Alkin‐Transformation umfasst 1) eine chemische N‐O‐Spaltung, 2) Fragmentmodifizierung und 3) Zusammenbau.
DNA–DNA cross‐linking agents constitute an important family of chemotherapeutics that non‐specifically react with endogenous nucleophiles and therefore exhibit undesirable side effects. Here we ...report a cationic Sondheimer diyne derivative “DiMOC” that exhibits weak, reversible intercalation into duplex DNA (Kd=15 μm) where it undergoes tandem strain‐promoted cross‐linking of azide‐containing DNA to give DNA‐DNA interstrand crosslinks (ICLs) with an exceptionally high apparent rate constant kapp=2.1×105 m−1 s−1. This represents a 21 000‐fold rate enhancement as compared the reaction between DIMOC and 5‐(azidomethyl)‐2′‐deoxyuridine (AmdU) nucleoside. As single agents, 5′‐bispivaloyloxymethyl (POM)‐AmdU and DiMOC exhibited low cytotoxicity, but highly toxic DNA‐DNA ICLs were generated by metabolic incorporation of AmdU groups into cellular DNA, followed by treatment of the cells with DiMOC. These results provide the first examples of intercalation‐enhanced bioorthogonal chemical reactions on DNA, and furthermore, the first strain‐promoted double click (SPDC) reactions inside of living cells.
Zusammengeknipst: Ein auf dem Sondheimer‐Diin basierendes Interkalationsreagens vermittelt sehr schnelle, spannungsgeförderte Doppelklick(SPDC)‐Reaktionen zwischen Azidgruppen und gegenüberliegenden DNA‐Strängen unter Bildung von Interstrangverknüpfungen. Diese Ergebnisse repräsentieren die ersten Beispiele von interkalationsverstärkten bioorthogonalen chemischen Reaktionen von DNA.
A modular synthesis of short chain length and medium chain length poly(3‐hydroxyalkanoate)s‐b‐poly(ethylene glycol) (PHAs‐b‐PEG) diblock copolymers is described. First, length‐controlled oligomers of ...hydrophobic poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBHV), poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) (PHBHHx), and poly(3‐hydroxyoctanoate‐co‐hydroxyhexanoate) (PHOHHx) containing a carboxylic acid end group were obtained by thermal treatment, with molar masses ranging from 3 800 to 15 000 g · mol−1. After quantitative functionalization with propargylamine, ligation with azide‐terminated poly(ethylene glycol) of 5 000 g · mol−1 was accomplished using the copper (I) catalyzed azide alkyne cycloaddition (CuAAC). Well‐defined diblock copolymers were obtained up to 93% yield, with molar masses ranging from 9 900 to 23 100 g · mol−1. All products were fully characterized using 1H NMR, COSY, SEC, TGA, and DSC.
The synthesis of a series of short chain length and medium chain length poly(3‐hydroxyalkanoate)s‐ b‐poly(ethylene glycol) (PHAs‐ b‐PEG) diblock copolymers is presented. Length‐controlled PHAs oligomers were prepared by thermal treatment and subsequently alkyne‐functionalized. Ligation of azide‐terminated PEG was accomplished using the copper (I) catalyzed azide alkyne cycloaddition (CuAAC) leading to well‐defined copolymers, as proven by NMR and SEC analyses.
•Empowerment evaluation celebrates its 21st anniversary.•It operates in over 16 countries, from squatter settlements to Google.•Donaldson, Scriven, Patton, and Alkin comment on the ...approach.•Contributors and proponents of empowerment evaluation adopt a critical friend’s perspective.
This special topic edition of E&PP presents the insights of luminaries in the field who have helped shape empowerment evaluation with their critiques, concerns, and congratulations. We celebrate their contributions to empowerment evaluation. This special topic edition of E&PP presents their comments about an evaluation approach that, according to president Stewart Donaldson, has “gone viral” across the globe (Donaldson, 2015).
To set the stage for these critical friends’ comments, additional context for their discussion is provided. In addition, this special topic edition concludes with a brief comment on their thoughts.
Cu(I) kataliziranim reakcijama sulfonil- odnosno fosforil-azida i terminalnih alkina nastaje intermedijar ketenimin koji reagira s nukleofilima kao što su voda, alkoholi, amini, piroli ili indoli, ...pri čemu nastaju odgovarajući amidi, imidati, amidini i supstituirani heterocikli, u jednom reakcijskom koraku. Te selektivne reakcije zbivaju se pri blagim reakcijskim uvjetima (sobna temperatura, prisustvo zraka i vode), bez steričkog i elektronskog utjecaja supstituenata na ishod reakcije.
Ge‐streckte Isomere: Die anorganischen Bi‐ und Tricyclohexanderivate A–C weisen neuartige Koordinationsweisen von Nitrosoarenen an Metalle auf. DFT‐Rechnungen zeigen, dass die Stukturen A und B zwei ...von drei möglichen stabilen Isomeren der diradikalischen Stammverbindung mit unterschiedlichen Ge‐Ge‐Bindungslängen entsprechen.
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