Synthesis and Polymerization of a Chiral Liquid Crystal Diacrylate Exhibiting Smectic A* and C* Phases

The alignment and cross-linking of chiral liquid crystal (LC) phases has been used to generate ordered noncentrosymmetric polymer networks with a variety of interesting optical and transducer properties. Examples of intrinsically chiral LC diacrylates which exhibit chiral smectic phases are rare because of the difficulties associated with the design of such monomers. We are presenting the stereospecific synthesis and subsequent photopolymerization of a chiral smectic diacrylate which is derived from (S)-ethyl lactate. This monomer exhibits an enantiotropic smectic A* phase from 49 to 71 [ddot]C upon heating at 0.5 [ddot]C/min and from 71 to 39 [ddot]C upon cooling at the same rate. The smectic A* phase of the chiral monomer can be homeotropically and homogeneously aligned and subsequently photopolymerized to yield highly uniform, noncentrosymmetric polymer films of predefined symmetry Upon rapid cooling at 5 [ddot]C/min, the monomer also exhibits a metastable, monotropic ferroelectric smectic C* phase from approximately 35 to 33 [ddot]C. The cross-linking of this metastable phase will also be discussed.

Key Words

• ferroelectric liquid crystals,
• cross-linked,
• smectic,
• diacrylates