title: Inducement by directional fields of rotational and translational phase ordering in polymer liquid-crystals.
abstract: The effects of aligning fields on models of polymer liquid crystals were simulated using the dissipative particle dynamics method. Exposing a liquid crystal of rod-like particles to a directional field causes a stabilization of the phases with orientational order, shifts the isotropic-nematic and nematic-smectic-A phase transitions to higher temperatures, makes the transitions continuous beyond a critical field strength, and induces weak para-nematic alignment in the zero-field isotropic phase. The interplay of liquid-crystalline ordering, microphase separation, and an alignment field endows the diblock and triblock copolymers studied here with rich phase behavior. The simulations suggest that field-induced orientational ordering can give rise to positional ordering. Reversely, positional ordering resulting from rod-coil demixing may be accompanied by orientational ordering, which is enhanced by external fields. For highly asymmetric rod-coil copolymers, the microphase separation pattern formed by the rigid segments can be altered by an aligning field.
authors.affiliation: Department of Physics and Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia. asunaidi@kfupm.edu.sa
authors.forename: A
authors.initials: A
authors.lastname: AlSunaidi
authors.forename: W K
authors.initials: WK
authors.lastname: den Otter
authors.forename: J H R
authors.initials: JH
authors.lastname: Clarke