Synthesis of chiral conjugated polymers bearing azobenzene moieties using cholesterics

The preparation of chiral conjugated polymers bearing bulky groups (azobenzene) from achiral monomers in a cholesteric liquid crystal medium is discussed. The polymers, prepared in this manner, display aggregation and complementary mirror-image Cotton effects. This preparation helps in obtaining optically active polymers with functions such as light isomerization. Such approach allows chiral polymers to be obtained without crystal catalysts or chiral monomers through the use of cholesteric liquid crystal as a chiral polymerization method. The cholesteric liquid crystalline field provides a simple means of molecular design for chiral polymers with functional groups, and the solvent themselves are repeatedly reusable. Chiral conjugated polymers consisting of three thiophene rings with an azobenzene moiety in the monomer repeat unit are also prepared. This new synthetic method can be also be applied for the preparation of chiral polymers having various functions.