Mesogene-polymer backbone coupling in side-chain polymer liquid crystals, studied by high magnetic-field-induced alignment

Phys Rev Lett. 2003 Jan 17;90(2):025501. doi: 10.1103/PhysRevLett.90.025501. Epub 2003 Jan 14.

Abstract

We show that cooling side chain polymer liquid crystals in a magnetic field, from the isotropic to nematic and subsequently to the glass phase, results in a macroscopically ordered, transparent, and strongly birefringent material. The aligned samples retain their properties after the field is removed and can be dealigned only by heating them to the isotropic phase. To induce alignment, a threshold field B(th) is necessary, which strongly depends on the chemical structure details. B(th) reflects the strength of mesogene-polymer backbone coupling, and we will show that this interaction is responsible for the stability of the induced alignment at zero field.