Transmission Electron Microscope Observation by Surface Replica Method for Layer Undulation in Solid X₁ Phase of Banana Molecule

Abstract

The smectic X 1 phase formed from the banana 4-bromo-1,3-phenylenebis[4-(4-n-tetradecanoxyphenyliminomethyl)benzoate] (4Br-P-14-O-PIMB) molecule, possesses a distinct two-dimensional structure with a long-range density modulation of $17:5 nm along the layer. The X 1 phase is formed upon cooling from the well-known B 2 phase, and then its characteristic modulated structure is retained at room temperature. A transmission electron microscopic (TEM) observation was performed for shadowed replica film which imprints the surface structure of the homeotropically aligned X 1 phase. The modulation was detected as clear stripes with periodicities ranging from 15 to 18 nm, which agree with the modulation length determined by X-ray measurement. The results confirm that the periodicity along the layer is not due to the simple density modulation occurring within a smooth layer, but can be explained by the layer undulation that creates the crests and troughs.

Atomic Force Microscope Observation of Nano-Ordered Undulation Structure Formed by Bent-Shaped Molecules

“…This periodicity is well-matched with the estimated periodicities by the X-ray experiment 15) and TEM observation. 16) The amplitude of undulation which has not been determined in previous studies was estimated as 2:7 AE 0:5 nm. This value is roughly half the layer thickness of the B2 phase.…”

“…A filmy replica method of transmission electron microscope (TEM) measurement has provided the undulation mode, the width of which is comparable to that estimated from the Xray methods. 16) Here, we have performed an atomic force microscopy (AFM) in order to investigate the material-air surface morphology for homeotropically aligned samples. The AFM observation coupled with the microscopic one can be expected for giving us straight information of the fluctuation of layers, i.e., periodic distance and amplitude between crests and troughs in the undulation mode of layers.…”

“…This value is roughly half the layer thickness of the B2 phase. 16) Figure 4 illustrates the layer undulation occurring in the two dimensional lattice of a ¼ 17:5 nm, c ¼ 5:34 nm, and ¼ 81:1 that is determined from the X-ray study.…”

Banana-shaped molecular architecture: Formation of large columns composed of two concentrically enclosed layers

“…8,9 Recently, we have investigated the banana-shaped molecules having a bromine atom on the central core of P-n-O-PIMB, the so-called 4Br-P-n-O-PIMB (n: carbon number of the alkoxy tail, n ¼ 4-14). [10][11][12][13] For these homologous molecules, we found three room-temperature solid phases with interesting dissipation structures (see Fig. S1 in ESI †).…”

“…4 A, and g ¼ 81.1 was determined from a SR X-ray pattern. [11][12][13] The X2 phase revealed as a B4 phase because it exhibited characteristic dark and chiral domain textures in addition to the typical wide angle X-ray diffraction (WAXD) pattern. However, the structure of the X3 phase has not yet been examined in detail.…”