Supramolecular systems constructed by crown ether-based cryptands

Cryptands, seen as a kind of crown ether derivatives, have attracted much attention because of their three dimensional spatial structures and additional binding sites. Moreover, by changing functional groups on the third arm, various stimuli-responsive host–guest systems were obtained, which have played key roles in the construction of functional supramolecular systems. The recent advances in supramolecular systems constructed by crown ether-based cryptands, and further applications, especially in supramolecular polymers are summarized in this digest paper.     

Competing through altering the environment: A cross-diffusion population model coupled to transport–Darcy flow equations

We consider an evolution model describing the spatial population distribution of two salt tolerant plant species, such as mangroves, which are affected by inter- and intra-specific competition (Lotka–Volterra), population pressure (cross-diffusion) and environmental heterogeneity (environmental potential). The environmental potential and the Lotka–Volterra terms are assumed to depend on the salt concentration in the root region, which may change as a result of mangroves’ ability to uptake fresh water and leave the salt of the solution behind, in the saturated porous medium. Consequently, partial differential equations modelling the population dynamics on the surface are coupled with Darcy–transport equations modelling the salt and pressure-velocity distribution in the subsurface. We prove the existence of weak solutions of the coupled problem and provide a numerical discretization based on a stabilized mixed finite element method, which we use to numerically demonstrate the behaviour of the system.     

Stable All‐Organic Radicals with Ambipolar Charge Transport

A series of neutral long‐lived purely organic radicals based on the stable [4‐(N‐carbazolyl)‐2,6‐dichlorophenyl]bis(2,4,6‐trichlorophenyl)methyl radical adduct (Cbz‐TTM) is reported herein. All compounds exhibit ambipolar charge‐transport properties under ambient conditions owing to their radical character. High electron and hole mobilities up to 10^?2 and 10^?3 cm² V^?1 s^?1, respectively, were achieved. Xerographic single‐layered photoreceptors were fabricated from the radicals studied herein, exhibiting good xerographic photosensitivity across the visible spectrum.     

Sulfonated dendrimer‐ and hyperbranched polyglycerol‐PBIOO® blend membranes for fuel cells

A new sulfonated dendrimer with an arylene ether sulfone backbone has been synthesized, fully characterized, and blended with PBIOO^® to prepare acid‐base proton‐conducting membranes under different conditions and with different composition ratios. Water‐soluble sulfonated hyperbranched polyglycerols of different molecular weights were also used as the acidic components. Membrane properties such as ion‐exchange capacity, water uptake, thermal stability, proton conductivity, and morphology have been studied and discussed. The nature of the acidic component and the morphology of the membranes had a marked influence on the final properties. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 69–80     

Electrophoretic characterization of insulin growth factor (IGF-1) functionalized magnetic nanoparticles

The synthesis of composite nanoparticles consisting of a magnetite core coated with a layer of the hormone insulin growth factor 1 (IGF-1) is described. The adsorption of the hormone in the different formulations is first studied by electrophoretic mobility measurements as a function of pH, ionic strength, and time. Because of the permeable character expected for both citrate and IGF-1 coatings surrounding the magnetite cores, an appropriate analysis of their electrophoretic mobility must be addressed. Recent developments of electrokinetic theories for particles covered by soft surface layers have rendered possible the evaluation of the softness degree from raw electrophoretic mobility data. In the present contribution, the data are quantitatively analyzed based on the theoretical model of the electrokinetics of soft particles. As a result, information is obtained on both the thickness and the charge density of the surrounding layer. It is shown that IGF-1 adsorbs onto the surface of citrate-coated magnetite nanoparticles, and adsorption is confirmed by dot-blot analysis. In addition, it is also demonstrated that the external layer of IGF-1 exerts a shielding effect on the surface charge of citrate-magnetite particles, as suggested by the mobility reduction upon contacting the particles with the hormone. Aging effects are demonstrated, providing an electrokinetic fingerprint of changes in adsorbed protein configuration with time.     

New light on the ring-chain equilibrium of a hydrogen-bonded supramolecular polymer based on a photochromic dithienylethene unit and its energy-transfer properties as a storage material

A novel, bifunctional, quadruple hydrogen-bonding ureido-pyrimidinone (UPy) unit bridged by photochromic dithienylethene (1) has been synthesized, which affords linear assemblies in solution and undergoes concentration-dependent ring-opening polymerization. The two UPy functional groups of 1 can dimerize intramolecularly to form a cyclic monomer with the two thienyl rings fixed in a parallel conformation, which prohibits its photocyclization. We exploited the photochemical reactivity and resonance difference of the linker of the bis-UPy derivative as well as using the more typical (1)H NMR, DOSY, and Ubbelohde viscometry methods to investigate for the first time the ring-chain polymerization mechanism. Moreover, we fabricated a mixed polymer film with a fluorescent dye noncovalently endcapping the linear photochromic assemblies through quadruple hydrogen bonds, which showed nondestructive fluorescent read-out ability for data storage by fluorescence resonance energy transfer (FRET) from the fluorescent dye to the closed form of the diarylethene.     

Re-examination of the anion derivatives of isoflavones by radical fragmentation in negative electrospray ionization tandem mass spectrometry: experimental and computational studies

This paper reports theoretical and experimental studies of gas‐phase fragmentation reactions of four naturally occurring isoflavones. The samples were analyzed in negative ion mode by direct infusion in ESI‐QqQ, ESI‐QqTOF and ESI‐Orbitrap systems. The MS/MS and MSⁿ spectra are in agreement with the fragmentation proposals and high‐resolution analyses have confirmed the formulae for each ion observed. As expected, compounds with methoxyl aromatic substitution have showed a radical elimination of ?CH₃ as the main fragmentation pathway. A second radical loss (?H) occurs as previously observed for compounds which exhibit a previous homolytic ?CH₃ cleavage (radical anion) and involves radical resonance to stabilize the anion formed. However, in this study we suggest another mechanism for the formation of the main ions, on the basis of the enthalpies for each species. Compounds without methoxy substituent dissociate at the highest energies and exhibit the deprotonated molecule as the most intense ion. Finally, energy‐resolved experiments were carried out to give more details about the gas‐phase dissociation reaction of the isoflavones and the results are in agreement with the theoretical approaches. Copyright © 2011 John Wiley & Sons, Ltd.