A capacitive humidity sensor using cross-linked cellulose acetate butyrate

This paper reports on the fabrication of a new capacitive humidity sensor having good characteristics and being robust enough to be considered as a component in industrial processes.This sensor is manufactured using a mixture of three cellulose acetate butyrates cross-linked by a melamine formaldehyde resin as sensing material. Details of the fabrication process and sensor characteristics such as linearity, sensitivity, hysteresis, response time, maximum operating temperature or physical and chemical stresses influence are included

Fragility of a thermoplastic polymer. Influence of main chain rigidity in polycarbonate

We present new data on a vitreous polycarbonate (PC) and its fragility index. Measurements have been performed by means of differential scanning calorimetry (DSC). A comparison with other data already published in this field and concerning other linear polymers is made. We show that when experiments are performed by means of DSC, the use of the glass-forming liquid fragility concept does not lead to large enough variations of the fragility index values. Thus, any correlation with structural characteristics of linear polymers, is not possible, except in the case of main chain rigidity

9-(Dicyano­methyl­idene)fluorene–tetra­thia­fulvalene (1/1)

The title compound, C16H8N2·C6H4S4, crystallizes with the fluorene derivative placed in a general position and two half tetra­thia­fulvalene (TTF) mol­ecules, each completed to a whole mol­ecule through an inversion center. The fluorene ring system is virtually planar (r.m.s. deviation from the mean plane = 0.027 Å) and the dicyano group is twisted from the fluorene plane by only 3.85 (12)°. The TTF mol­ecules are also planar, and their central C=C bond lengths [1.351 (8) and 1.324 (7) Å] compare well with the same bond length in neutral TTF (ca 1.35 Å). These features indicate that no charge transfer occurs between mol­ecules in the crystal; the compound should thus be considered a cocrystal rather than an organic complex. This is confirmed by the crystal structure, in which no significant stacking inter­actions are observed between mol­ecules

Study of poly(bisphenol A carbonate) relaxation kinetics at the glass transition temperature

In this work, the variations of the relaxation times are investigated above and below the glass transition temperature of a model amorphous polymer, the polycarbonate. Three different techniques (calorimetric, dielectric and thermostimulated currents) are used to achieve this goal. The relaxation time at the glass transition temperature was determined at the temperature dependence convergence of the relaxation times calculated with dynamic dielectric spectroscopy (DDS) for the liquid state and thermostimulated depolarisation currents (TSDC) for the vitreous state. We find a value of s(Tg) = 110 s for PC samples. The knowledge of the temperature dependence, s(T), and the value s(Tg) enables to determine the glass-forming liquid fragility index, m. We find m = 178 ± 5

(S)-(+)-N-Benzyl­idene-1-(1-naphth­yl)ethyl­amine

In the title chiral aldimine, C19H17N, the azomethine group is not fully conjugated with the phenyl substituent: the dihedral angle between phenyl and C*—N=C mean planes is ϕ3 = 23.0 (2)°. Compared with the earlier DFT-B3LYP/6–31 G(d) computations from the literature, the C=N—C*—C(naph­thyl) torsion angle, found at ϕ2 = −118.0 (2)° in the X-ray structure, does not match the angle calculated for the potential minimum energy at ϕ2 = 0°. However, this angle is close to the second potential energy minimum at ϕ2 = −120° which is ca. 8.5 kJ mol−1 above the global energy minimum. Thus, the reported X-ray structure corresponds to the second most likely (according to DFT) conformer, allowing the existence of other polymorphs to be anti­cipated

Chloridotris(penta­fluoro­benzene­thiol­ato-κS)[tris­(4-fluoro­phen­yl)phosphine-κP]osmium(IV)

The title complex, [Os(C6F5S)3Cl(C18H12F3P)], displays a trigonal-bipyramidal OsIV coordination geometry with the S atoms of three thiol­ate ligands occupying the equatorial positions. The thiol­ate penta­fluoro­phenyl substituents are all placed above the equatorial plane, forming a claw-like cavity which accommodates the chloride ligand with a normal Os—Cl bond length. The phosphine ligand trans to the chloride ligand reveals a short Os—P bond length compared to other chloride–phosphine OsIV complexes (average = 2.40 Å). This strong bonding indicates that the inductive effect of the F atoms in the phosphine does not affect significantly its basicity, compared to triphenyl­phosphine. This feature is also consistent with the known poor trans influence of Cl−. The crystal packing involves π–π contacts between inversion-related thiol­ate C6F5 rings, with a centroid–centroid separation of 3.659 (8) Å

Diallyl 5-[(4-hexyl­oxyphen­yl)imino­meth­yl]-m-phenyl­ene dicarbonate

The title mol­ecule, C27H31NO7, an imine derivative bearing both carbonate and allyl functionalities, was synthesized in the hope of obtaining a mesogenic polymerizable material. The allyl­carbonate arms are fully disordered over two sets of sites, reflecting a large degree of rotational freedom about σ bonds [occupancies: 0.665 (9)/0.335 (9) for one substituent, 0.564 (9)/0.436 (9) for the other]. In contrast, the hexyl chain is ordered, and presents the common all-trans extended conformation. The benzene rings connected via the imine group make a dihedral angle of 9.64 (11)°. In the crystal, the Y-shaped mol­ecules are weakly associated into centrosymmetric dimers through pairs of C—H⋯O(hex­yl) contacts. The resulting layers of dimers, approximately parallel to (25), are closely packed in the crystal, allowing π⋯π inter­actions between benzene rings of neighboring layers: the separation between the centroid of the benzene ring substituted by allyl­carbonate and the centroid of the benzene ring bearing the hex­yloxy group in the adjacent layer is 3.895 (1) Å

2,2′-(Propane-1,3-di­yl)bis­(2H-indazole)

The title mol­ecule, C17H16N4, is a bis-indazole crystallized in the rare 2H-tautomeric form. Indazole heterocycles are connected by a propane C3 chain, and the mol­ecule is placed on a general position, in contrast to the analogous compound with a central C2 ethane bridge, which was previously found to be placed on an inversion center in the same space group. In the title mol­ecule, indazole rings make a dihedral angle of 60.11 (7)°, and the bridging alkyl chain displays a trans conformation, resulting in a W-shaped mol­ecule. In the crystal, mol­ecules inter­act weakly through π–π contacts between inversion-related pyrazole rings, with a centroid–centroid separation of 3.746 (2) Å

Specific heat studies of pure Nb3Sn single crystals at low temperature

Specific heat measurements performed on high purity vapor-grown Nb$_3$Sn crystals show clear features related to both the martensitic and superconducting transitions. Our measurements indicate that the martensitic anomaly does not display hysteresis, meaning that the martensitic transition could be a weak first or a second order thermodynamic transition. Careful measurements of the two transition temperatures display an inverse correlation between both temperatures. At low temperature specific heat measurements show the existence of a single superconducting energy gap feature.Comment: Accepted in Journal of Physics: Condensed Matte

(–)-(S)-N,N′-Bis[1-(1-naphth­yl)eth­yl]­oxalamide

The title mol­ecule, C26H24N2O2, displays C 2 symmetry, with the mol­ecule located on a twofold axis perpendicular to the plane of the oxalamide unit –NH—CO—CO—NH–. The oxalamide core deviates from planarity, as reflected by the O=C—C=O and N—C—C—N torsion angles of 164.3 (5) and 163.2 (5)°, respectively. The naphthyl groups are oriented toward the same face of the oxalamide mean plane and make a dihedral angle of 43.76 (8)°. This conformation is suitable for the formation of inter­molecular N—H⋯O hydrogen bonds, giving noncentrosymmetric dimers incorporating R 2 2(10) ring motifs. These nonbonding inter­actions propagate along the 61 screw axis normal to the mol­ecular twofold axis, resulting in a single-stranded right-handed helix parallel to [001]. In the crystal, Δ helices are arranged side-by-side and inter­act through π–π contacts between naphthyl groups. The shortest centroid–centroid separation between inter­acting benzene rings is 3.623 (4) Å