Enthalpy of formation of crystalline surfactant molecular complexes

The standard enthalpy of formation of novel chemical species — crystalline cationic surfactant molecular complexes — was studied to elucidate the bonding nature, serially scanning over the different surfactant chain-length homologs and various additive species. The enthalpy was not large, but was obviously dependent on the surfactant chain length and the chemical nature of the additive species. The typical complexes comprising long alkyl chain surfactants were formed endothermally, while in short alkyl chain homologs the process was exothermic. By examining the thermal aspect, it was suggested that the typical complexes of long alkyl-chain surfactants were derived not from attractive energetic force factors, but rather from entropic factors associated with the occurrence of severe disorder caused by heavy thermal agitation in the complex crystalline state.     

Nuclear magnetic resonance studies of helical dipyrromethene-zinc complexes

[formula: see text] Analysis of helical chirality within dinuclear dipyrromethene-Zn(II) complexes has been achieved with the use of 1H NMR spectroscopy. The use of AgFOD and chiral lanthanide shift reagents gives fully resolved resonances attributable to two diastereomeric helical complexes.     

Influence of the crystalline phase on the molecular mobility of PVDF

Dielectric relaxation and pyrocurrent of PVDF were studied by thermostimulated current spectroscopy. The transition spectrum of the material was investigated by differential scanning calorimetry. Two well-resolved relaxation peaks have been observed in the temperature range [?100–100°C]. The molecular mechanisms of these phenomena have been discussed, based on a comparative study of α-PVDF. and β-PVDF. The β relaxation mode is located at ?41°C in α-PVDF and is slightly shifted toward higher temperatures in the stretched material. This mode has been ascribed to the dielectric manifestation of the glass transition (T_g) of PVDF. It is comprised of two components corresponding to the free and constrained amorphous phases, respectively, in the order of increasing temperatures. The α_c transition/relaxation has been associated with molecular motions in the crystalline/amorphous interphase. At higher temperatures, a compensation phenomenon corresponding to cooperative movements liberated at the Curie transition has been observed in β-PVDF. © 1993 John Wiley & Sons, Inc.     

Nuclear magnetic resonance of oriented molecules in lyotropic liquid crystalline media: p-cresol

Proton-proton distance ratios and order parameters for partially oriented p-cresol in a lyotropic mesophase derived from potassium laurate are obtained. The order parameters are the largest yet found for an ordered solute in a nematic-like lyotropic system. The dipolar couplings and structural data were independent of the rotational potential from 0–200 cal mol^?1.     

Nuclear magnetic resonance study of low molecular weight polychlorotrifluoroethylene

The molecular motion of low molecular weight polychlorotrifluroethylene of different molecular weights between 500 and 1300 was investigated by means of broad-line nuclear magnetic resonance measurements. The line width and second moment of the resonant absorption lines were obtained at temperatures from 77 to 300°K. The line narrowing for low molecular weight samples takes place in one step. In samples higher than 900 in molecular weight, however, there appears to be a glass transition process, and the line narrowing tends to occur in three steps. The line narrowing due to local molecular motion becomes observable with increasing molecular weight.     

Theoretical investigation of the halogen bonded complexes between carbonyl bases and molecular chlorine

The halogen bonded complexes between six carbonyl bases and molecular chlorine are investigated theoretically. The interaction energies calculated at the CCSD(T)/aug‐cc‐pVTZ level range between ?1.61 and ?3.50 kcal mol^?1. These energies are related to the ionization potential, proton affinity, and also to the most negative values (V_s,min) on the electrostatic potential surface of the carbonyl bases. A symmetry adapted perturbation theory decomposition of the energies has been performed. The interaction results in an elongation of the Cl? Cl bond and a contraction of the CF and CH bonds accompanied by a blue shift of the ν(CH) vibrations. The properties of the Cl₂ molecules are discussed as a function of the σ*(Cl? Cl) occupation, the hybridization, and the occupation of the Rydberg orbitals of the two chlorine atoms. Our calculations predict a large enhancement of the infrared and Raman intensities of the ν(Cl? Cl) vibration on going from isolated to complexed Cl₂. © 2015 Wiley Periodicals, Inc.     

Local modes of molecular mobility in comb-shaped liquid crystalline ionomers containing alkaline metal ions

Molecular mobility of the comb-shaped copolymer poly(4-[6-(acryloyloxy)hexyloxy]benzoic acid-co-butyl acrylate) and Li- and Rb-containing LC ionomers based on this polymer was studied at low temperatures by the methods of dielectric spectroscopy and thermally stimulated depolarization current. The above copolymers are shown to experience the γ₂, γ₁, and β-processes, which are related by the reorientation of the end СООН groups, by the mobility of a spacer, and by the reorientation of mesogenic fragments (dimers of oxybenzoic acids) with respect to a long axis, respectively. The formation of multiplet structures in ionomers leads to a suppression of the intensity of the β-process that relates with a partial breakdown of hydrogen-bonded dimmers and with a decrease of their molecular mobility.