Electrostrictive Energy Conversion of Polyurethane with Different Hard Segment Aggregations

This work reported the electrostriction of polyurethane (PU) with different aggregations of hard segments (HS) controlled by dissimilar solvents: N,N-dimethylformamide (DMF) and a mixture of dimethyl sulfoxide and acetone denoted as DMSOA. By using atomic force microscopy and differential scanning calorimetry, the PU/DMSOA was observed to have larger HS domains and smoother surface when compared to those of the PU/DMF. The increase of HS domain formation led to the increase of transition temperature, enthalpy of transition, and dielectric constant (0.1 Hz). For the applied electric field below 4 MV/m, the PU/DMSOA had higher electric-field-induced strain and it was opposite otherwise. Dielectric constant and Young’s modulus for all the samples were measured. It was found that PU/DMF had less dielectric constant, leading to its lower electrostrictive coefficient at low frequency. At higher frequencies the electrostrictive coefficient was independent of the solvent type. Consequently, their figure of merit and power harvesting density were similar. However, the energy conversion was well exhibited for low frequency range and low electric field. The PU/DMSOA should, therefore, be promoted because of high vaporizing temperature of the DMSOA, good electrostriction for low frequency, and high induced strain for low applied electric field.

Enthalpy of formation of cubic yttria-stabilized zirconia

Oxide melt solution calorimetric measurements were made to determine the enthalpy of formation of cubic-yttria-stabilized zirconia (c-YSZ) with respect to the oxides m-ZrO2 and C-type YO1.5. The enthalpy of formation can be fit either by a quadratic equation or by two straight line segments about the minimum near x = 0.40. The quadratic fit gives a strongly negative interaction parameter, Ω=-93.7 ± 12.0 kJ/mol, but does not imply regular solution behavior because of extensive short-range order. In this fit, the enthalpy of transition of m-ZrO2 to c-ZrO2, 9.7 ± 1.1 kJ/mol, is in reasonable agreement with earlier estimates and that of C-type to cubic fluorite YO1.5, 24.3 ±14.4 kJ/mol, is consistent with an essentially random distribution of oxide ions and anion vacancies in the high-temperature fluorite phase. The two straight-line segments give 6.1 ± 0.6 kJ/mol and 5.5 ± 2.5 kJ/mol for these transitions, respectively. The latter value would imply strong short-range order in cubic fluorite YO1.5. Clearly more complex solution thermodynamic descriptions need to be developed. The enthalpy of transition from the disordered c-YSZ phase to the ordered δ-phase at 25 °C was also measured and was 0.4 ± 1.6 kJ/mol. No energetic difference between the disordered c-YSZ phase and the ordered δ-phase underscores the importance of short-range order in c-YSZ. Enthalpy data were combined with Gibbs free energy data to calculate entropies of mixing. Using the quadratic fit, negative excess entropy of mixing in the cubic solid solution, relative to a system with maximum randomness on cation and anion sublattices, was found and was another indication of extensive short-range order in c-YSZ.

Kristallstruktur von 1,1'-Dimethyl-4,4'-bipyridinium-octachlorodiantimonat(III) / Crystal Structure of 1,1'-Dimethyl-4,4'-bipyridinium-octachlorodiantimonate(III)

The title compound was prepared by reaction of SbCl3 with 1,1′-dimethyl-4,4′-bipyridinium-chloride in methanol. The single crystal structure gave the following data: [C12H14N2][Sb2Cl8] (1) space group PI, Nr. 1, with a = 570.68(7) pm, b = 938.57(14) pm, c = 1174.27(11)pm, α = 66.72(9)°, β = 89.304(12)°, γ = 78.684(11)°, and Z = 1. The compound has a small SHG effect and a phase transition at 272 °C with an enthalpy of transition of 6.54 kJ mol-1 .

Thermotropic mesomorphism in aqueous dispersions of 1-palmitoyl-2-oleoyl- and 1,2-dilauroyl-phosphatidylglycerols in the presence of excess Na+ or Ca2+

1-Palmitoyl-2-oleoyl-sn-glycero-3-phospho-rac-glycerol (POPG) and 1,2-dilauroyl-sn-glycero-3-phospho-rac-glycerol (DLPG) have been made by the conversion of the appropriate lecithins in the presence of crude phospholipase D and excess glycerol. Aqueous dispersions of the lipids have been examined by differential scanning calorimetry and 31P-nuclear magnetic resonance spectroscopy. When dispersed in excess Na+ at pH 7, POPG and DLPG underwent gel to liquid-crystalline phase transitions at −2.0 ± 1.3 and −3.7 ± 1.9 °C, respectively. The enthalpy of transition for POPG in excess Na+ was 6.2 ± 0.3 kcal∙mol−1 (1 cal = 4.1868 J), but the value for DLPG in Na+ was variable. In the presence of excess Ca2+ at pH 7, both phospholipids displayed complex thermotropic mesomorphism. For DLPG in the presence of excess Ca2+, thermal events did not occur at the same temperatures as did those for POPG in excess Ca2+. The complexity of the observed behaviour may have arisen because of the formation of intermediate forms which slowly interconverted to more stable forms.