| Abstract: | We have studied the temperature dependence of the pyroelectric coefficient, dielectric constant and spacings of polar LB-films building from molecules of p-(p-octadecyloxyphenylazo)benzenesulfonamide (18-OABS) with a large dipole moment. The films were deposited by the Langmuir-Schaefer method. A significant pyroelectric effect in the films proved them to be polar. The periodicity of structure in films was approximately equal to the length of the molecules used. An irreversible transition at 90°C from polar to nonpolar phase has been observed in these films. At this transition the structural period of the films changes (39Å ⟹ 69Å). Also these LB-films exhibited several structure transitions. The films did not show a single solid-to-liquid transition but were liquid-crystalline. In the liquidcrystal state the films have several smectic mesophases. Transitions to the mesophases take place at 124°C (69Å ⇔︁ 63Å) and at 136°C (63Å ⇔︁ 41Å). During the transitions the structural periods of the films and the value of dielectric constant change. |
