Authors:Bin Dong, Christian H. Galka, Lutz H. Gade, Lifeng Chi, and René M. Williams
nanocrystals are formed by self assembly of
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
-Bu substituted analogue of BPP, is used to
develop a model for the internal molecular structure of the rod shaped
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.
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.
Authors:Shaoxu Wang, Zihang Huang, Jianhai Wang, Yansheng Li, and Zhicheng Tan
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 hydrogenbonding action
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 hydrogenbonding.
The contribution of
Authors:Qianqian Xing, Qing Fu, Yu Jin, and Xinmiao Liang
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 hydrogenbonding
Authors:R. Cierpiszewski, D. Rusińska-Roszak, J. Szymanowski, W. Mickler, and E. Uhlemann
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
Authors:S. K. Adhya, P. C. Srivastava, and B. K. Banerjee
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.