The static deformation of the asymmetric Japanese bow: modelling bow asymmetries with the elastica theory

Meccanica - The static deformation of symmetric bow limbs has been widely studied in the last century. However, asymmetries in shape and length which correspond to a more realistic situation, have...     

A new pyridine-based 12-membered macrocycle functionalised with different fluorescent subunits; coordination chemistry towards Cu(II), Zn(II), Cd(II), Hg(II), and Pb(II)

The coordination chemistry of the new pyridine-based, N2S2-donating 12-membered macrocycle 2,8-dithia-5-aza-2,6-pyridinophane (L1) towards Cu(II), Zn(II), Cd(II), Hg(II), and Pb(II) has been investigated both in aqueous solution and in the solid state. The protonation constants for L1 and stability constants with the aforementioned metal ions have been determined potentiometrically and compared with those of ligand L2, which contains a N-aminopropyl side arm. The measured values show that Hg(II) in water has the highest affinity for both ligands followed by Cu(II), Cd(II), Pb(II), and Zn(II). For each metal ion considered, 1:1 complexes with L1 have also been isolated in the solid state, those of Cu(II) and Zn(II) having also been characterised by X-ray crystallography. In both complexes L1 adopts a folded conformation and the coordination environments around the two metal centres are very similar: four positions of a distorted octahedral coordination sphere are occupied by the donor atoms of the macrocyclic ligand, and the two mutually cis-positions unoccupied by L1 accommodate monodentate NO3- ligands. The macrocycle L1 has then been functionalised with different fluorogenic subunits. In particular, the N-dansylamidopropyl (L3), N-(9-anthracenyl)methyl (L4), and N-(8-hydroxy-2-quinolinyl)methyl (L5) pendant arm derivatives of L1 have been synthesised and their optical response to the above mentioned metal ions investigated in MeCN/H2O (4:1 v/v) solutions.     

Thermoresponsive super water absorbent hydrogels prepared by frontal polymerization

Frontal polymerization was used as an alternative technique for the preparation of super water absorbent hydrogels obtained from acrylamide and 3‐sulfopropyl acrylate, potassium salt (SPAK) in the presence of N,N′‐methylene‐bisacrylamide as a crosslinker. All samples were synthesized in dimethyl sulfoxide, and their swelling behavior in water was investigated. It was found that their features are dependent on the monomer ratio used, which influenced the porous morphology, and consequently, the swelling capability. The swelling ratio ranges from about 1000% for the acrylamide homopolymer up to 14,000% for the sample containing 87.5 mol % of SPAK, thus indicating that this parameter can be easily tuned by using the appropriate monomer ratio. The affinity towards water was eventually confirmed by contact angle analysis. Polymer hydrogels made from at least 62.5 mol % SPAK exhibit a thermoresponsive behavior, with a lower critical solution temperature of ～30 °C. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2486–2490, 2010     

Effect of soy protein isolate on the thermal, mechanical and morphological properties of poly (-caprolactone) and corn starch blends

The development of biodegradable polymers is considered to be a good alternative to decrease the volume of the plastic waste disposed into the environment every year. The use of natural polymers as raw materials to develop polymer blends and composites has increased the demand for renewable sources such as starch and soy protein.In this work, the authors prepared and characterized the thermal, mechanical and morphological properties of blends based on poly (-caprolactone) and modified corn starch, with added soy protein isolate (SPI) and sorbitol. All samples were processed by extrusion in a single-screw extruder and hot pressing. It was observed that the addition of modified corn starch and SPI were responsible for the reduction of thermal and mechanical properties of the materials, compared to pristine PCL. However, with increasing amounts of SPI and the reduction of starch incorporated into the samples, their properties tend to recover. The insertion of soy protein isolate in the formulations was done with the aim of balancing the C/N ratio of the blend, which plays a key role in the biodegradation process of these materials.     

Palladium‐Catalyzed Intramolecular Carbene Insertion into C(sp3)−H Bonds

A palladium‐catalyzed carbene insertion into C(sp³)?H bonds leading to pyrrolidines was developed. The coupling reaction can be catalyzed by both Pd⁰ and Pd^II, is regioselective, and shows a broad functional group tolerance. This reaction is the first example of palladium‐catalyzed C(sp³)?C(sp³) bond assembly starting from diazocarbonyl compounds. DFT calculations revealed that this direct C(sp³)?H bond functionalization reaction involves an unprecedented concerted metalation–deprotonation step.     

Effect of limonene on the frontal ring opening metathesis polymerization of dicyclopentadiene

The frontal ring opening metathesis polymerization (FROMP) of dicyclopentadiene (DCPD) in the presence of limonene, using second generation Grubbs’ catalysts, is reported. The effect of limonene on the amount of catalyst and the typical frontal polymerization parameters, as maximum temperature (T_max) and velocity of the front (V_f), is studied. In addition, the influence of limonene on the mechanical properties of the polymeric samples is reported. Finally, a deep study on the swelling properties of polymers is done. It has been demonstrated that limonene acts as both inhibitor and solvent of the catalyst. The T_max, V_f, T_g, and Young modulus values decrease as the amount of limonene increases, and the polymer samples swell in THF depending on the amount of limonene. All results indicate that the limonene addition on FROMP of results in advantages on the polymerization reaction and its parameters and on the final polymer properties. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 63–68     

Electronic states of a single layer of pentacene: standing-up and flat-lying configurations

The electronic properties of a single layer (SL) of pentacene molecules are investigated by high-resolution UV photoemission and near-edge X-ray absorption spectroscopy in different configurations of the SL, either standing up on an aromatic self-assembled monolayer or planar on a bare Cu(001) substrate. The weakly interacting pentacene molecules in the standing-up SL present a semiconducting character, and the empty states distribution reflects that of gas-phase pentacene, while the planar pentacene-Cu system shows a metallic interface with redistribution of the empty molecular states. The highest-occupied molecular orbital lineshape in the weakly interacting SL shows a double structure, attributed to two nonequivalent molecules in the ordered configuration.     

On the origin of satellite peaks in valence photoemission from CO ON Cu(110)

The valence-level photoelectron spectrum of CO absorbed on copper surfaces exhibits extra features in the region 10–20 eV below E_F which are attributed to multielectron excitations. We have recorded the satellite intensity as a function of photon energy in the system CO/Cu(110) using synchrotron radiation. It is found that the occurrence of all satellites, including some which are observed for the first time, can be explained in terms of the SCF Xα SW model calculations by Messmer et al.     

Existence and Multiplicity Results for the Nonlinear Klein-Gordon Equation

In this work, we study the multiplicity of solutions for a stationary nonhomogeneous problem associated to the nonlinear one-dimensional Klein-Gordon Equation. We prove that the existence of positive solutions is equivalent to the solvability of a scalar equation 2F(M) = 1, where F is a real function depending on V. Moreover, we prove some existence and multiplicity results for the Dirichlet problem in the superlinear case.     

CuPc molecules adsorbed on Au(1 1 0)-(1 × 2): growth morphology and evolution of valence band states

We present the growth morphology, the long-range ordering, and the evolution of the valence band electronic states of ultrathin films of copper phthalocyanine (CuPc) deposited on the Au(1 1 0)-(1 × 2) reconstructed surface, as a function of the organic molecule coverage. The low energy electron diffraction patterns present a (5 × 3) reconstruction from the early adsorption stages. High-resolution UV photoelectron spectroscopy data show the disappearance of the Au surface states related to the (1 × 2) reconstruction, and the presence of new electronic features related to the molecule-substrate interaction and to the CuPc molecular states. The CuPc highest occupied molecular orbital gradually emerges in the valence band, while the interface electronic states are quenched, upon increasing the coverage.