Chiral smectic liquid-crystalline polyacrylates with variously spaced and substituted biphenylene units

Abstract

Four new classes of Chiral liquid-crystalline polyacrylates A-n to D-n based on variously spaced and substituted biphenylene mesogens have been prepared. Spacer segments of n(= 5 – 11) methylene groups were used, and the chiral substituents were the (S)-2-methylbutoxy (A-n), (S)-1-methylheptyloxy (B-n), (S)-2-chloro-3-methylbutanoyloxy (C-n), or (2S,3S)-2-chloro-3-methylpentanoyloxy (D-n) groups. The polyacrylates exhibited a strong tendency to form the smectic A mesophase, sometimes in polymorphic sequences. In particular, on varying the length of the alkylene spacer of polyacrylates A-n the structure of the chiral smectic A phase evolved from bilayer (n⩽ 6) to interdigitated (n= 7) and to monolayer (n > 7). Depending on the nature of the chiral substituent, chiral smectic C and chiral nematic mesophases were also observed in a few samples. The polyacrylates appeared to be suitable candidates for studies of the electroclinic response in the chiral smectic A phase.