Self-healing polymers
with microphase-separated structure are plagued
with inferior self-healing efficiency at room temperature due to a
lack of dynamic interactions in hard domains. Herein, we describe
a novel strategy of multiphase active hydrogen bonds (H-bonds), toward
realizing fast and efficient self-healing at room temperature, even
under harsh conditions. The core conception is to incorporate thiourea
moieties into microphase-separated polyurea network to form multistrength
H-bonds, which destroy the crystallization of hard domains and, at
the same time, insert the dynamic reversible H-bonds in both hard
and soft segments, accounting for the surprisingly self-healing performances.
The synthesized polymeric material, poly(dimethylsiloxane)–4,4′-methylenebis(phenyl
isocyanate)–1,1′-thiocarbonyldiimidazole, completely
recovers all of the mechanical properties within 4 h at room temperature
after rupture. Significantly, self-healing process can also take place
at low temperature (restoration with an 85% efficiency in 48 h at
−20 °C) or in the water (restoration with a 95% efficiency
in 4 h). Depending on the cleavage/reformation of multiphase H-bonds,
the material exhibits unprecedented ultrastrechability and notch-insensitiveness.
It can be stretched up to 31 500% without fracture and reach
a notch-insensitive stretching of up to 18 000%. These exceptional
characteristics inspired us to fabricate highly stretchable self-healable
underwater conductor and protective self-healing film for suppressing
shuttling of polysulfides and preventing crack propagation in S cathode,
which provide the pathway for applications in underwater electronic
devices or advanced Li–S batteries.
Aktive Kupfer-und Eisenzentren dominieren das Gebiet der biologischen Sauerstoffchemie [1] und spielen wichtige Rollen in der homogenen [2] und der heterogenen Katalyse. [3,4] Kupferproteine sind an der reversiblen Disauerstoff-Koordination (H‰mocyanin), [5] an der mit der Oxidation von Substraten gekoppelten Zwei-Elektronen-Reduktion zu Peroxid (Amin-, Galactose-und Catechol-Oxidasen), [6] an der Aktivierung zur Hydroxylierung (Dopamin-b-Hydroxylase, Peptidylglycin-a-hydroxylierende Monooxygenase, Tyrosinase und partikul‰re Methan-Monooxygenase) [6,7] und an der mit der Substratoxidation einhergehenden Vier-Elektronen-Reduktion zu Wasser (Laccase, Ascorbat-Oxidase, Caeruloplasmin und Fet3p) [7] sowie an Protonen-Pumpen (Cytochrom-c-Oxidase, die auch H‰m-Eisenzentren enth‰lt) beteiligt. [8] Die bislang bekannten, an Disauerstoff-Koordination, -Aktivierung und -Reduktion beteiligten Kupferproteine sind, geordnet nach dem Strukturtyp des aktiven Zentrums, in [*] Prof.
A new bis-β-diketone, 3,3'-bis(4,4,4-trifluoro-1,3-dioxobutyl)biphenyl (BTB), has been designed and prepared for the synthesis of a series of dinuclear lanthanide complexes [Ln(2)(BTB)(3)(C(2)H(5)OH)(2)(H(2)O)(2)] [Ln = Eu (1), Gd (2)], [Ln(2)(BTB)(3)(DME)(2)] [Ln = Nd (3), Yb (4); DME = ethylene glycol dimethyl ether] and [Eu(2)(BTB)(3)(L)(2)] [L = 2,2-bipydine (5); 1,10-phenanthroline (6); 4,7-diphenyl-1,10-phenanthroline (7)]. Complexes 1-7 have been characterized by various spectroscopic techniques and their photophysical properties are investigated. X-ray crystallographical analysis reveals that complexes 1, 3 and 4 adopt triple-stranded dinuclear structures which are formed by three bis-bidentate ligands with two lanthanide ions. The complexes 1 and 3-7 display strong visible red or NIR luminescence upon irradiation at ligand band around 372 nm, depending on the choice of the lanthanide. The solid-state photoluminescence quantum yields and the lifetimes of Eu(3+) complexes are determined and described.
The insertion of an aryne into a C-S bond can suppress the addition of an S nucleophile to the aryne in the presence of palladium. Catalyzed by Pd(OAc)₂, a wide range of α-carbamoyl ketene dithioacetals readily react with arynes to selectively afford functionalized 2-quinolinones in high yields under neutral reaction conditions by a C-S activation/aryne insertion/intramolecular coupling sequence. The attractive feature of the new strategy also lies in the versatile transformations of the alkythio-substituted quinolinone products.
Microcystin-RR (MC-RR) is one of the most common cyanotoxin microcystins in fresh water and is of great concern due to its potential hepatotoxicity. In the present study, Bi(2)WO(6) was synthesized with a hydrothermal method by varying the pH of the reaction solution in the range of 1-11. The surface area of the catalysts decreased, but the crystallinity and crystal size increased with the pH. The adsorption and degradation capacities of the catalysts decreased with increasing the preparation solution pH. The Bi(2)WO(6) prepared at pH 1 (Bi(2)WO(6)-pH1) displayed the highest adsorption and degradation capacity to MC-RR even though it consisted of randomly aggregated particles. Nearly 100% of MC-RR at 10 mg L(-1) was removed after 30 min of irradiation of near-ultraviolet light (300-400 nm) in a solution with Bi(2)WO(6) concentration of 0.2 g L(-1). The photodegradation efficiency of Bi(2)WO(6)-pH1 was greater in acid medium than in basic solutions. Several intermediate products were observed and identified by liquid chromatography/mass spectrometry/mass spectrometry, and a unique photodegradation pathway was proposed. It was assumed that a photo-Kolbe process happened at the site carboxyl acid group of the d-Glu residue by the photogenerated holes, producing a hydroperoxyl product at m/z 513.8. This intermediate could be further decomposed to an alcohol product at m/z 505.8 and a ketone product at m/z 504.8. The aromatic ring and diene bond of the Adda chain could also be attacked by the holes and form phenol and diol products.
A new β-diketone, 2-(2,2,2-trifluoroethyl)-1-indone (TFI), which contains a trifluorinated alkyl group and a rigid indone group, has been designed and employed for the synthesis of two series of new TFI lanthanide complexes with a general formula [Ln(TFI)(3)L] [Ln = Eu, L = (H(2)O)(2) (1), bpy (2), and phen (3); Ln = Sm, L = (H(2)O)(2) (4), bpy (5), and phen (6); bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline]. X-ray crystallographic analysis reveals that complexes 1-6 are mononuclear, with the central Ln(3+) ion eight-coordinated by six oxygen atoms furnished by three TFI ligands and two O/N atoms from ancillary ligand(s). The room-temperature photoluminescence (PL) spectra of complexes 1-6 show strong characteristic emissions of the corresponding Eu(3+) and Sm(3+) ions, and the substitution of the solvent molecules by bidentate nitrogen ligands essentially enhances the luminescence quantum yields and lifetimes of the complexes.
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