Abstract
The smectic X1 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 X1 phase is formed upon cooling from the well-known B2 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 X1 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.