Conformations of the main chain and structure of comb-shaped liquid-crystalline poly(methacrylates) with a varying molecular mass

The structure and conformations of comb-shaped LC poly(methacrylates) with a varied length of an alkoxy substituent of a phenylbenzoate mesogenic group in isotropic, nematic, and smectic phases were studied by small-angle neutron scattering. The radii of gyration of a polymer chain in direction parallel and perpendicular to the director of a liquid crystal R_∥ and R_⊥ were measured. The anisotropy of the polymer chain shape in the nematic and smectic phases was found to be R_⊥/R_∥ ∼ 1.4 and R_⊥/R_∥ ∼ ·2.7, respectively, thereby indicating the oblate conformation of macromolecules. It was demonstrated that the radii of gyration of the polymer in the smectic phase depends on the degree of polymerization z = 42-406 through the following analytical dependence R_⊥ = (0.78 ± 0.04)z^{(0.59 ± 0.06)} and R_∥ = (1.5 ± 0.4)z^{(0.3 ± 0.08)}. It was demonstrated for the first time that the anisotropy of a polymer coil increases with the increasing molecular mass of the polymers.