On the Origins of Spontaneous Polarization in Tilted Smectic Liquid Crystals

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Science  03 Nov 1995:
Vol. 270, Issue 5237, pp. 783-786
DOI: 10.1126/science.270.5237.783


The rapid electrooptic response of ferroelectric liquid crystals-stratified (smectic) melts exhibiting spontaneous electric polarization-makes them candidates for the next generation of electrooptic shutters and liquid crystal displays. The model advanced here suggests that polarity is indigenous to tilted smectics and that spontaneous polarization derives from the packing constraints mesogens experience, a tilt-dependent correlation of molecular conformation with orientation. First-rank orientational order parameters (CxX) are nonzero with a tilt- (temperature-) dependent magnitude, and under certain packing conditions, the sign of CxX varies with tilt. These results have a direct bearing on experimental observations because most ferroelectric liquid crystals exhibit a tilt-dependent spontaneous polarization and some show an inversion of the sign of the polarization.