Synthesis of Novel (Meth)acrylates with Variable Hydrogen Bond Interaction and Their Application in a Clear Viscoelastic Film.

Clear viscoelastic films (CVFs) have many applications in the display industry. Acrylic monomers containing a hydrogen bond (H-monomer) are often used in the preparation of CVF to increase the cohesion and form favorable interactions with the display substrate. Common H-monomers face a counterbalance between the glass transition temperature (Tg) and the hydrogen-bonding association constant (Ka). Strong hydrogen bonding often leads to a high Tg and high modulus, which are unfavorable in certain applications such as foldable display. To solve these problems, four types of hydrogen-bonding (meth)acrylic monomers (carbamate acrylate, carbamate methacrylate, urea acrylate, and urea methacrylate) with different Ka and Tg were readily synthesized. Among them, urea acrylates displayed the highest Ka while still maintaining moderate Tg. These H-monomers were copolymerized with 2-ethylhexyl acrylate (EHA) and cross-linked to obtain a series of copolymers (H-copolymers) as pressure-sensitive adhesives. After the characterization of rheology, optics, and peel adhesion, urea-acrylic H-copolymers showed the best overall performance by combining great optical property (>98% in transmittance, < 1% in haze) and mechanical performance (8-12 N/25 mm in peel adhesion, 84-92% in creep recovery). This work provides a new path to prepare acrylic CVF for flexible display application.

Carbon bowl-confined subnanometric palladium-gold clusters for formic acid dehydrogenation and hexavalent chromium reduction.

Formic acid (FA), a high-value product of CO2 hydrogenation and biomass conversion, is considered a promising liquid organic hydrogen carrier for its high hydrogen content, easy accessibility, and relative stability. The development of an efficient heterogeneous catalyst toward FA dehydrogenation and Cr(VI) reduction by FA is needed to boost its sluggish kinetics but still remains a challenge. Herein, uniformly dispersed subnanometric PdAu alloy clusters (i.e., 0.9 nm) were successfully prepared and confined by amine-functionalized carbon bowls (ACB). By virtue of the tiny size and abundant active sites of PdAu clusters, the promotional effect of surface amine groups, and electronic interaction between subnanometric PdAu clusters and support, this as-prepared PdAu/ACB catalyst exhibits superior catalytic property for additive-free FA dehydrogenation (turnover frequency, 10597 h-1 at 323 K) and Cr(VI) reduction (rate constant, 0.47 min-1 at 298 K) under mild conditions, higher than most of the catalysts reported so far. This study offers insight into the design of efficient and durable catalysts for various catalytic applications in energy and environment.

Chromic hydroxide-decorated palladium nanoparticles confined by amine-functionalized mesoporous silica for rapid dehydrogenation of formic acid.

Formic acid (FA), one of the products of biomass conversion and CO2 reduction, has attracted much attention as a renewable liquid hydrogen carrier with a high hydrogen content (4.4 wt%). Searching for efficient catalysts to realize hydrogen evolution from FA are highly desired but challenging. Herein, ultrafine and mono-dispersed Pd-Cr(OH)3 nanoparticles (1.3 nm) loaded on amine-functionalized mesoporous silica (AFMS) have been prepared and applied as an effective catalyst for rapid hydrogen production from additive-free FA. The as-synthesized Pd-Cr(OH)3/AFMS catalysts exhibited efficient catalytic activity and 100% hydrogen selectivity and conversion toward FA dehydrogenation reaction without additives, giving an initial TOF value of 3112 h-1 at 323 K, which is comparable to most of the highly efficient heterogeneous catalysts reported so far under similar reaction conditions. This work provides a feasible idea for the design metal hydroxide-modified Pd-based efficient heterogeneous catalyst, which is expected to enhance the application of FA in fuel cells.

Highly Stretchable, Soft, and Clear Viscoelastic Film with Good Recoverability for Flexible Display.

The advancement of flexible electronic devices has prompted new material development for the display application. For flexible display, a suitable clear viscoelastic film (CVF) is essential to bond different layers in a display stack in order to improve the visualization and durability during the repeated folding process. However, it is challenging to integrate different properties in the CVF by overcoming many contradictory requirements, such as low modulus/glass transition temperature (Tg) and high adhesion or high recoverability and good stress-relaxation. In this work, a CVF was prepared using an interpenetrating polymer network (IPN) with bimodal chain length distribution, and it exhibited several favorable properties. The bimodal elastomer was composed of short-chain polyurethane (PU) and long-chain polyacrylate. The long-chain polyacrylate network provided a large amount of entanglement that conferred stretchability, adhesion, and stress-relaxation, whereas the short PU chain network acted as an entropy spring and contributed mostly to the recoverability. The experimental data suggested the presence of a hydrogen-bonding interaction and interlocked polymer chains between the two networks. When the components of the IPN are adjusted, the CVF can simultaneously achieve good stress-relaxation, high strain recovery at large strain (1000%), high toughness, clarity, and adhesion. Moreover, the CVF displayed low glass transition temperature (-57 °C) and low storage modulus (20 to 30 kPa at room temperature). To the best of our knowledge, this is the first report using the IPN concept to prepare a CVF with well-balanced properties.

UV Curable Robust Durable Hydrophobic Coating Based on Epoxy Polyhedral Oligomeric Silsesquioxanes (EP-POSS) and Their Derivatives.

Hydrophobic coatings have considerable potential applications in many fields. Ease of operation and high durability are essential for practical use. Fast curing and being solvent-free are a plus, and if they possess certain characteristics (antigraffiti, good adhesion, high hardness, heat resistance, wide range of applicability, etc.) at the same time, it is a dream solution. Herein, a facile one-step approach with the above features was reported for a UV curable robust hydrophobic coating based on Epoxy Polyhedral Oligomeric Silsesquioxanes (EP-POSSs). The structure and surface morphology of these EP-POSSs and their derivatives were systematically studied. Because of the core-in-cage structure which was constructed by repeating units of R-Si(O1/2)3 and the strong covalent bonds of Si-C and Si-O, the coatings displayed high pencil hardness (6-8H), high thermal stability with initial decomposition temperature around 350-400 °C, and a high water contact angle (up to 108.06°) even after outdoor exposure for a month. These POSSs and their derivatives are expected to find uses in various applications such as stain resistance, self-cleaning, scratch resistance, and cigarette moxibustion resistance of wood furniture, kitchenware, and medical and industrial appliances.

Regio- and Diastereoselective Construction of Functionalized Benzo[b]oxepines and Benzo[b]azepines via Recyclable Gold(I)-Catalyzed Cyclizations.

The heterogeneous gold-catalyzed cyclization of (o-alkynyl)phenoxy- or N-(o-alkynylphenyl)tolylsulfonamidoacrylates with alcohols has been developed by using an MCM-41-anchored diphenylphosphine-Au(I) complex [MCM-41-Ph2P-AuNTf2] as the catalyst under mild reaction conditions, yielding diverse functionalized benzo[b]oxepines or benzo[b]azepines with good to high yields and excellent diastereoselectivity. This heterogenized gold(I) catalyst exhibits a comparable activity to homogeneous Ph3PAuNTf2 and can be facilely recovered by a simple filtration of the reaction solution and reused more than seven times with almost a consistent catalytic efficiency.

Rapid Synthesis of Large-Size Fe2O3 Nanoparticle Decorated NiO Nanosheets via Electrochemical Exfoliation for Enhanced Oxygen Evolution Electrocatalysis.

A novel nonprecious Fe2O3 nanoparticle decorated NiO nanosheet (Fe2O3 NPs@NiO NSs) composite has been obtained by a rapid one-pot electrochemical exfoliation method and can be used as an efficient oxygen evolution reaction (OER) catalyst. In the nanocomposite, the Fe2O3 NPs are uniformly anchored on the ultrathin graphene-like NiO nanosheets. At the same time, we also studied the influence of the Fe/Ni molar ratio on the morphology and catalytic activity. The Fe2O3 NPs@NiO NSs nanocomposite possessed a high BET surface area (194.1 m2 g-1), which is very conducive to the charge/mass transfer of electrolyte ions and O2. Owing to the unique two-dimensional (2D) heterostructures and rational Fe content, the as-prepared Fe2O3 NPs@NiO NSs show high catalytic performance, a low overpotential at 10 mA cm-2 (221 mV), a small Tafel slope (53.4 mV dec-1), and 2000 cycle and 20 h long-term durability. The introduction of Fe2O3 NPs is beneficial to accelerating charge transport, increasing the electrochemically active surface area (ECSA), and thus improving the release of oxygen bubbles from the electrode surface.

The first total synthesis of rebaudioside R.

With easily available monosaccharides and steviol as starting materials, the first total synthesis of rebaudioside R with a xylosyl core in the C13-OH linked sugar chain was accomplished via two distinct approaches. The first approach features the stepwise installation of branch-sugar residues via an order of C2-OH first and then C3-OH of the xylosyl core, laying a firm foundation for the synthesis of analogues with different branch sugars, while the second route features the introduction of the C13 trisaccharide sugar chain via a convergent strategy, securing the overall synthetic efficiency. Through the synthetic study, the effect of protecting groups (PGs) at the vicinal hydroxy group on the reactivity of OH acceptors was illustrated.

The Structural Revision and Total Synthesis of Carambolaflavone A.

The synthesis of both enantiomers of carambolaflavone A, the antidiabetic and flavonoid C-glycoside, was achieved for the first time via a 12-longest-linear-step with 16% (l-fucose) and 11% (d-fucose) overall yields. Through the synthetic investigation, the adverse effect of 4A MS in Suzuki C-glycosylation was disclosed, the mechanism of hydrogen-bonded-phenol involved Suzuki C-glycosylation was clarified, and the authentic structure of carambolaflavone A was also determined.

Pd/Cu-catalyzed dual C-H bond carbonylation towards the synthesis of fluorazones.

Pd/Cu catalyzed oxidative dual C-H bond activation/carbonylation still remains a great challenge due to the generation of by-products via C-C bond formation. Herein we developed a straightforward Pd/Cu-catalyzed oxidative dual C-H bond carbonylation process to access biologically and pharmaceutically important fluorazones from easily available N-aryl pyrroles and CO. A wide range of functional groups were well tolerated in this transformation, and O2 could be utilized as the only terminal oxidant to promote the oxidative carbonylation process.

Zn(OTf)2 promoted rearrangement of 1,2-cyclopropanated sugars with amines: a convenient method for the synthesis of 3-polyhydroxyalkyl-substituted pyrrole derivatives.

A rearrangement reaction of 1,2-cyclopropanated sugars with alkylamines or arylamines promoted by Zn(OTf)2 is described. The method offers a series of 3-polyhydroxyalkyl-substituted pyrrole derivatives with multiple chiral centers in moderate to excellent yields. The epimerization is achieved by inverting the stereochemistry at the free hydroxyl group of the resulting pyrrole, which would give access to many more possible stereoisomers.

Palladium-catalysed oxidative cross-esterification between two alcohols.

A simple palladium-catalysed oxidative cross-coupling between two different alcohols was developed. Various benzylic alcohols could couple with aliphatic alcohols in excellent yields. The use of benzyl chloride as the oxidant and the amount of aliphatic alcohol were both important for achieving the reaction selectivity.

3,3-Bis(methyl-sulfan-yl)-1-(4-nitro-phen-yl)prop-2-en-1-one.

In the title compound, C11H11NO3S2, the S-Csp (2) bonds are shorter [1.746 (3) and 1.750 (2) Å] than the S-CH3 bonds [1.794 (3) and 1.806 (3) Å], which we attribute to d-π inter-actions between the S atoms and the C=C bond. The 1,1-bis-(methyl-sulfan-yl)-3-oxo-propyl-ene fragment and the 4-nitro-phenyl group are both almost planar, with the largest deviations from their mean planes being 0.053 (1) and 0.017 (2) Å, respectively. The dihedral angle between the two planes is 35.07 (7)°. Mol-ecules in the crystal are linked into a three-dimensional network by C-H⋯S and C-H⋯O hydrogen bonds.

1-(4-Chloro-phen-yl)-2-(1,3-diazepan-2-yl-idene)ethanone.

In the title compound, C13H15ClN2O, there are two crystallographically independent but conformationally similar (E)-mol-ecules in the asymmetric unit [dihedral angles between the phenyl ring and a common planar fragment of the 1,3-diazepane moiety = 47.34 (16) and 48.00 (16)°]. The seven-membered ring system adopts a chair conformation in both molecules. In the crystal, N-H⋯O hydrogen bonds lead to chains extending along the b-axis direction.

[6-(Furan-2-yl)-7-nitro-2,3,4,6,7,8-hexa-hydro-1H-pyrido[1,2-a]pyrimidin-9-yl](phen-yl)methanone.

The asymmetric unit of the title compound, C19H19N3O4, contains two mol-ecules with very few conformational differences; a C atom in the pyrimidine ring in one of the mol-ecules is disordered in a 0.688 (15):0.312 (15) ratio. In both mol-ecules, the fused pyridine and pyrimidine rings adopt half-chair conformations. The dihedral angles between the furan and benzene rings are 81.00 (13) and 84.99 (10)° in the two mol-ecules. The mol-ecular structure is consolidated by intra-molecular N-H⋯O hydrogen bonding. In the crystal, C-H⋯O hydrogen bonds connect the molecules into a three-dimensional network.

[Survey on recent infection of human immunodeficiency virus among men who have sex with men in Tianjin during 2008 - 2009].

OBJECTIVE: To study the situation of HIV infections among men who have sex with men (MSM) in Tianjin during 2008 - 2009 and to provide reasonable evidence for intervention strategy. METHODS: Transect investigations in MSM were conducted three times during 2008 - 2009. Blood samples were collected and detected to identify the recent HIV infection with IgG-capture BED-enzyme immunoassay (BED-CEIA) before HIV incidence was estimated. RESULTS: 1799 specimens were tested and the HIV prevalence rates of each study were 6.7%, 8.6% and 6.2%, while the incidence rates were 2.7%, 2.5% and 2.8%, respectively. The estimated incidence rates among these testees were 5.36% and 5.52% per year in 2008 and 2009. RESULTS: of this study showed that the HIV incidence stabilized at high level among MSM in Tianjin, calling for the effective interventions be taken for HIV/AIDS control and prevention.