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Abstract: The present work reports an experimental investigation on the influence of glycine (NH2CH2COOH) substitution in the polar properties and the critical dynamics of the molecular ferroelectric betaine arsenate, (CH3)3NCH2COO·H3AsO4. The dielectric dispersion (20Hz<ν<3MHz) and the thermally induced displacement currents are investigated in detail over the extended Curie region of the system (130K

The heat capacity of the [[N(C2H5)4]2CdBr4 crystal is measured by the calorimetric method in the temperature range from 80 to 300 K. It is revealed for the first time that the temperature dependence of the heat capacity C p ( T) exhibits an anomaly associated with the first-order phase transition occurring at the temperature T 1 = 226.5 K. A long relaxation of the temperature of the crystal is observed in the temperature range 150–165 K. [ABSTRACT FROM AUTHOR]

The heat capacity of [(C2H5)2NH2]2CuCl4 crystals, both nonirradiated and γ-irradiated to a dose of 107 R, was studied in the temperature interval 90–330 K by adiabatic calorimetry. The temperature dependence of Cp(T) was found to have a peak-shaped anomaly in the region of the thermochromic phase transition (PT) at T = 322.7 K. Smoothened experimental heat capacity data were used to calculate the changes in the thermodynamic functions. The changes in the entropy and enthalpy of the thermochromic PT were determined to be ΔS = 42 J K–1mol–1 and ΔH = 13 653 J mol–1 for the nonirradiated crystals and ΔS = 39 J K–1mol–1 and ΔH = 12 120 J mol–1 for the irradiated crystals, respectively. Irradiation of a [(C2H5)2NH2]2CuCl4 crystal by γ rays to a dose of 107 R was shown to shift the PT point toward lower temperatures by ΔT≈1.7 K. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

The heat capacity of dimethylammoniumgallium sulfate crystals was measured using adiabatic calorimetry in the range 80–300 K before and after gamma irradiation with doses of 107 and 108 R. Heat-capacity anomalies were revealed around the ferroelastic-ferroelectric (135 K) and ferroelectric-paraelectric (119 K) phase transitions. Gamma irradiation was found to reduce the temperature stability range of the ferroelectric phase. [ABSTRACT FROM AUTHOR]

The heat capacity of a [NH2(CH3)2]5Cd3Cl11 crystal was studied calorimetrically in the temperature interval 100–300 K. The Cp(T) dependence indicates that, as the temperature is lowered, phase transitions occur at temperatures T1 = 176.5 K and T2 = 123.5 K. The thermodynamic characteristics of this crystal were determined. It is shown that the transition at T2 = 123.5 K is an incommensurate–commensurate phase transformation and that the transition at T1 = 176.5 K is a normal–incommensurate phase transition. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

The unit cell parameters a and c of nonirradiated [N(C2H5)4]2ZnBr4 crystals in the temperature region 90–300 K and of samples irradiated with γ rays to doses of 106 and 5 × 106 R in the 270-to 300-K interval were measured using x-ray diffraction. The data obtained were used to derive the thermal expansion coefficients αa and αc. It is shown that the parameter a increases and the parameter c decreases with increasing temperature. In the vicinity of the phase transition (PT) at T = 285 K, the temperature dependences of a( T) and c( T) reveal anomalies in the form of jumps and the αa( T) and αc( T) curves have a maximum and a minimum, respectively. The heat capacity of nonirradiated and irradiated [N(C2H5)4]2ZnBr4 samples was measured by adiabatic calorimetry. A maximum was found in the C p( T) curve at T = 285 K. Both x-ray diffraction and heat capacity measurements showed that the PT temperature decreased after γ irradiation. [ABSTRACT FROM AUTHOR]

In-plane aligned nanofibers of organic 2-methyl-4-nitroaniline (MNA) were produced by the electrospinning technique using a 1:1 weight ratio with poly(l-lactic acid). The fibers are capable of enormous efficient optical second harmonic generation as strong as pure MNA crystals in powder form. Structural, spectroscopic, and second harmonic generation polarimetry studies show that the MNA crystallizes within the fibers in an orientation in which the aromatic rings of MNA are predominantly orientated edge-on with respect to the plane of the fiber array and with their dipole moments aligned with the fiber axis. The results show that the electrospinning technique is an effective method to fabricate all-organic molecular functional devices based on polymer nanofibers with guest molecules possessing strong nonlinear optical and/or polar properties.

All the residues of the title compound, (C(5)H(6)N(3)O(2))[ReO(4)]·H(2)O, are located on general crystallographic positions. The 2-amino-5-nitro-pyridinium cation has a typical planar conformation with one of the nitro O atoms -0.058 (5) Å out of plane; the amine H atoms are also a little out of the main ring plane towards the opposite side of the aforementioned O atom [by 0.02 (4) and 0.04 (4) Å]. The perrhenate anion is nearly ideally tetra-hedral. Three distinct N-H⋯O hydrogen bonds give rise to C(8) zigzag chains running along [100]. R(4) (4)(12) rings involving the two hydrogen bonds in which the water mol-ecules inter-act with the perrhenate anions are also present.