Piezoelectricity and the structure of ferroelectric smectic C* liquid crystalline side-chain polymers

Abstract We discuss the local and global symmetry of chiral smectic C side-chain polymers. We argue on the basis of simple Ginzburg-Landau expansions that in polymeric systems the local symmetry can be C1 (compared to the conventional C2 symmetry), which gives globally (i.e. if averaged over many helical pitches) a C∞ symmetry (compared to the conventional D∞ symmetry). As a consequence ferroelectricity (or antiferroelectricity) has a non-vanishing component along the layer normal, thus allowing longitudinal piezoelectric and pyroelectric effects.