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

Abstract

ABSTRACT: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.

Progress in control of microdomain orientation in block copolymers – Efficiencies of various external fields

“…The first report of controlling orientation of block copolymer microdomains appeared in 1998 [57] where a 2.4 T magnetic field was imposed on a diblock copolymer comprising both block chains of liquid-crystalline polymers (LCP). Preferential orientation of microdomains was observed by SAXS.…”

Prediction of long‐term service performance of polymeric materials from short‐term tests: Creep and prediction of the stress shift factor of a longitudinal polymer liquid crystal

“…The reduced volume Q and the other reduced parameters are defined as follows: G = u/v*; T = TIT*: p = P/P* (3) where T and P are the thermodynamic temperature and pressure: T* and P* are the characteristic (hard-core) parameters for a given material. The former is related to the strength of interactions in the material.…”

Highly oriented and ordered double-helical morphology in ABC triblock terpolymer films up to micrometer thickness by solvent evaporation

“…Many techniques have been used to orient the cylindrical structures perpendicular to the substrate in the copolymer film, including surface affinity, 3-6 the application of shear force, 7 electric fields, [8][9][10][11] and magnetic fields. [12][13][14][15][16] In addition, surface roughness is critical for a vertical orientation. 17 However, few of these techniques can maintain the perpendicular orientation in the copolymer thick film over several micrometers.…”