Consideration of the spacer length in SmE phase induced by random copolymerization

Abstract

We synthesized series of side-chain liquid crystalline (SCLC) copolymers composed of an azobenzene (Az) monomer with decylene spacer and cyanobiphenyl (CB) monomers with different alkylene spacer lengths. The SCLC copolymers with the binary mesogens exhibit higher isotropic points compared to each homopolymer by differential scanning calorimetry and polarized microscope observation. The SCLC copolymers with relatively long spacer CB formed the highly ordered smectic (Sm) phases such as SmB and SmE which the homopolymer did not exhibit at room temperature by by X-ray scattering measurement. The Copolymers with CB spacer length of less than C8 did not exhibit SmE phase. Moreover, the smectic lamellar spacing of these copolymers was almost constant at 3.5-3.6 nm.