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The influence of intermolecular hydrogen bonding on some physical constants is clearly shown by comparing some thermal data for simple oxamides and thiooxamides.

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Rod-shaped nanocrystals are formed by self assembly of t -Bu-phenyl substituted tetra(carboxamido)perylenes (BPP) in different solvents. The structure and the dimensions of the nano-rods may be controlled by the choice of the hydrogen-bond accepting capacity of the solvent (DMSO, DMF, DMAc, HMPA), by the concentration and by the composition of solvent-mixture (by adding hydrogen-bond donating solvents), but is independent of the surface used for their deposition (mica, silicon, gold, glass). The different forms of aggregation were examined by AFM and SNOM and were correlated to UV-Vis absorption spectra of the aggregates in solution. The orientation of the transition dipole moment of the molecules in the nanocrystals has been determined by polarized fluorescence microscopy and, in combination with the crystal structure of the t -Bu substituted analogue of BPP, is used to develop a model for the internal molecular structure of the rod shaped aggregates.

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Abstract  

There is ample scope for modification of polyvinyl alcohol (PVA) to derive diverse range of properties because of the presence of hydroxyl group in its chain. In the present work, PVA has been modified to carboxymethylated polyvinyl alcohol (CPVA) — a carboxy-functionalized membrane material. Generally the cohesive energy density has incremental influence on the melting point and mechanical strength of a material but in this case of CPVA even though theoretical cohesive energy density of CPVA is lower than that of PVA but paradoxically its mechanical strength was found to be higher than that of PVA (∼202 vis-à-vis 207°C and ∼174 vis-à-vis ∼58 MPa, respectively). Calorimetric evaluation along with the energy balance concept have provided meaningful information to justify such paradoxical feature as a result of the dominating role of intermolecular hydrogen bonding in CPVA to compensate for its relatively lower cohesive energy density typically 0.05 J m−3/2. Thermal analysis has been made to examine the role of PVA and its carboxymethylated derivative (CPVA) towards moisture. It was observed that PVA membrane surface became sticky on exposure to water at 30°C for a period of 30 min, whereas under the same condition CPVA counterpart remained practically unaffected.

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Abstract  

The thermally induced phase separation behavior of hydrogen bonded polymer blends, poly(n-hexyl methacrylate) (PHMA) blended with poly(styrene-co-vinyl phenol) (STVPh) random copolymers having various vinyl phenol contents, was studied by temperature modulated differential scanning calorimetry (TMDSC).The enthalpy of phase separation was determined to be about 0.5 cal g–1 for one of the blends. A phase diagram was constructed from the TMDSC data for one of the blends. The kinetics of phase separation was studied by determining the phase compositions from the glass transition temperatures of quenched samples after phase separation. Subsequently, the phase separated samples were annealed at temperatures below the phase boundary to observe the return to the homogeneous state.

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Acta Alimentaria
Authors: A. Alberti, R. Amorati, M. Campredon, M. Lucarini, D. Macciantelli, and G. Pedulli

general treatment of hydrogen bond complexation constants in tetrachloromethane. J. Am. Chem. Soc. , 110 , 8534–8536. Guiheneuf G. A general treatment of hydrogen bond

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protonation of HCl-doped PANI [ 19 ]. Comparing to the corresponding peaks of pure PANI at 1308 and 1152 cm −1 , the peaks of the PANI/CeO 2 composite ( Fig. 1 a–d) shift slightly to lower wave numbers. This may be caused by the hydrogen bonding action

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point of a given compound is a function not only of molecular mass and molecular packing but also of intermolecular forces subtly related to the electronegativity/polarity, steric effects, and possible hydrogen bonding. The contribution of

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difference in retention behavior was attributed to that the aglycone in fraction a had one less hydroxyl than that in fraction c ( Figure 4 ). The silica column belonging to the polar stationary phase provided considerable hydrogen bonding

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Abstract  

The rate of copper extraction with individual 4-acyl-5-pyrazolones and the stability of various enolic and keto forms and their monohydrates were studied. The rate of extraction depends mainly upon the structure of substituent at position 4 and falls when the substituent becomes spacy. The effect of the substituent at position 1 is rather low. The enolic form with intramolecular hydrogen bonding is the most stable. It can form hydrates with water molecules without intramolecular hydrogen bond breaking.

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Thermal and infrared spectral studies of the urea-orthoboric acid complex are reported. The complex is formed through the elimination of 0.5 H2O molecule. Infrared spectral data show the presence of hydrogen-bonding and the force constant calculated for the N ... HO bond is found to be 4−5×10−5 dyne cm−1, which is for the order of a single bond and indicates strong hydrogen-bonding in the complex. A tentative structure for the complex is proposed.

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