Phase diagrams and optical properties of new menthyl-containing LC copolymers forming chiral mesophases

New comb-shaped LC copolymers based on phenyl benzoate and menthyl-containing monomers were synthesized. Phase behaviour, optical properties and structure of the synthesized copolymers with different compositions were studied. Specific features of the development of helical nematic and smectic mesophases (N*,N-B*,N-cyb*,N-re*,SmA*,SmF*, blue phases) were revealed. Special attention was paid to studying the structure and optical properties of the new chiral N-B* mesophase. For this unusual type of mesophase, a model accounting for the arrangement of the mesogenic group is suggested. It is stressed that the subscript B does not mean biaxial (a biaxial N phase is usually denoted N-b) and B refers to the hexagonal ordering of the side groups, similar to that in a SmB phase. An alternative nomenclature would be N-h, where subscript h refers to hexagonal as in Col(h0) for a hexagonally ordered columnar phase of a discogen.