Electric field alignment of nanofibrillated cellulose (NFC) in silicone oil: impact on electrical properties.

This work aims to study how the magnitude, frequency, and duration of an AC electric field affect the orientation of two kinds of nanofibrillated cellulose (NFC) dispersed in silicone oil that differ by their surface charge density and aspect ratio. In both cases, the electric field alignment occurs in two steps: first, the NFC makes a gyratory motion oriented by the electric field; second, NFC interacts with itself to form chains parallel to the electric field lines. It was also observed that NFC chains become thicker and longer when the duration of application of the electric field is increased.

Conformational disorder in 4-(5,5'-dibromo-2'-chloro-4,4'-bipyridyl-2-yl)benzaldehyde: role of pi-pi and halogen interactions.

The crystal packing of the title compound, C(17)H(9)Br(2)ClN(2)O, is governed by strong pi-pi stacking, where molecules are tightly bound within infinite (100) planes; these planes interact mainly through non-optimal pi-pi stacking where arene rings are noticeably displaced from perfect overlap, and also through halogen-halogen interactions. The aldehyde group shows conformational disorder, with a significant population difference between the two conformers; this difference is rationalized by the energetic analysis of the crystal packing using the PIXEL method, which also allows a decomposition of intermolecular interaction energy into Coulombic, polarization, dispersion and repulsion contributions. Using such an analysis, it is found that the main reason for this unequal population of the two conformers in the crystal is two hydrogen bonds that are present only for the major conformer.