Design and Investigation of a Side-Chain Liquid Crystalline Polysiloxane with a N_tb-Phase-Forming Side Chain

A new mesogenic non-symmetric dimeric monomer with a terminal olefin function, forming a twist bend nematic (N-tb) as well as a nematic (N) phase, was synthesized, using an enhanced synthetic methodology, which avoids isomerization of the terminal double bond in the preparation of the dimer. This monomer was attached to a pentamethyldisiloxane group, resulting in the SmA LC phase behavior of the ensuing material. Linking the monomer to a siloxane main chain resulted in nematic phase behavior. Detailed studies with the N-tb phase forming dimer DTC5C7 show full miscibility of the dimer and the new LC polymer in the LC state, suggesting that the side-chain LC polymer forms a N-tb phase as the low-temperature nematic phase. Copolymerizing the monomer with a cyanobiphenyl-based monomer allows us to tune the glass transition and phase behavior further.