Dino Ferri

Phase and orientational behaviors in liquid crystalline main‐chain/side‐group block copolymers

The phase and orientational behaviors of a series of liquid crystalline (LC) AB-type diblock copolymers comprising thermotropic main-chain (MC) polyester and side-group (SG) polymethacrylate blocks were investigated by X-ray diffraction. The MC and SG blocks were phase separated and gave rise to their individual mesophases that coexisted at equilibrium. The samples were oriented by using either a magnetic field or a mechanical field. In magnetically aligned samples both the MC and SG microphases were oriented with their smectic planes orthogonal to the magnetic field direction, independent of the copolymer composition. Mechanically aligned, fiber samples showed different orientations of the MC and SG smectic planes for different sample compositions. In this case the disposition of the smectic planes of the MC and SG blocks was driven by the relative length of the two blocks. Some features of the X-ray patterns of the copolymers were compared to those of the MC and SG homopolymers. In addition, the MC smectic domains crystallized on annealing without affecting the orientation that had been achieved by applying a magnetic field.

On the Peculiar Dynamic-Mechanical Behavior of an Azobenzene-Containing Mesomorphic Polyacrylate

Abstract The phenomenology of the α relaxation process in an amorphous and crystallized specimen of a side-chain LC polyacrylate, based on the azobenzene mesogenic unit, was investigated by thermal and dynamic-mechanical methods. A frequency and temperature analysis was performed. The relaxation behavior of the amorphous sample was described by the WLF equation. The α process of the semicrystalline sample was structured into two components α′ and α″, both following Arrhenius type activation law. This peculiar behavior has been tentatively related to the multidomain structure of the semicrystalline sample.