Dopants nonchiral smectics

In chiral-racemic mixtures, the magnitude of Pg varies essentially linearly with the enantiomeric excess. Important for applications is the more general case of a mixture of a nonchiral smectic-C host with a chiral dopant. The relation between Pg and the concentration of the chiral dopant in such mix-... 

Thus, in order to let Py survive, we can put small propellers on the molecules, i.e., make them chiral. We could for instance synthesize molecules with one or more asymmetric carbon atoms, but it would, in principle, also be sufficient to dissolve some chiral dopant molecule in the nonchiral smectic C in order to remove the mirror plane. This can, symbolically, be written... 

The symmetry approach to ferroelectricity in liquid crystals can be realized not only for individual substances but also for multicomponent systems. For low-molar-mass ferroelectric liquid crystals, most applications use LC mixtures with two main components a nonchiral matrix providing the tilted smectic structure and a chiral dopant [7]. As for the preparation of FLCPs, mixing of a smectic C polymer with a chiral dopant also results in a ferroelectric chiral smectic system [74]. Japanese authors [75,76] have carried out systematic studies on mixing tilted smectic polymers with low-molar-mass ferroelectric liquid crystals. 

There is one more, rather polymer-specific possibility for combining a tilted smectic matrix and a chiral dopant, namely copolymerization. Thus, a nonchiral methacrylate monomer inducing a tilted smectic phase was copolymerized with a chiral comonomer that forms a smectic A homopolymer only [77], The resulting copolymers ... 

In the case of low-molar-mass LCX the phenomenon of induced spontaneous polarization is well known and established in coaunerdal FLC mixtures. By doping smectic C materials with chiral dopants, spontaneous polarization can be induced. Advantages over pure Sr liquid crystals are tunable ferroelectric properties and high switching speed achievable by using a nonchiral. low-viscous Sc basic material and doping with small amounts of Ugh-polarization Sc substances. 

---