Synthesis and Properties of Smeclic Side-Chain Polymers

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Abstract
In the chiral smectic phase (i.e. the C phase), the molecules are arranged randomly in layers and tilted with respect to the normal layer. The symmetry plane of the ordinary smectic C structure is absent because the molecules are chiral. The only symmetry element is a twofold rotation axis which allows molecules to “flip-flop” head-to-tail. If there is any transverse electric molecular dipole moment, its component along this axis cannot be averaged to zero and so each Layer is spontaneously polarized. However, on passing from layer to layer the tilt direction of the molecules is turned through a small angle about an axis perpendicular to the layers and hence a helical structure is formed. The spontaneous polarization is rotated from one layer to the next about the helical axis and averages to zero in a bulk sample. Hence, the chiral smectic phase is ferroelectric only if the helical arrangement is suppressed.