Regular undulation and polarization modulation on the film surface of a planarly aligned SmC* polymer

Abstract

Chiral smectic C (SmC*) in a main-chain type of polymer exhibits undulations on its glassy film surface; these undulations are produced by the helical assembly of polymer conforming to the helical field of SmC*. In this study, we have found a polarization modulation superimposed on the undulation from the combined observations of Kelvin force microscopy (KFM) and atomic force microscopy (AFM) images. This modulation is caused by the spontaneous polarization of each smectic layer; its direction is parallel to the layer and perpendicular to the tilt direction of molecules within a layer, and rotates around the helical axis. The polarization modulation length corresponds perfectly to the undulation length, i.e., helical pitch of SmC*. By clarifying the relative direction of the spontaneous polarization to the tilt direction of mesogens, we described how the polymers are accommodated to produce such a regular undulation and polarization modulation.