Transient periodic dissipative structures in nematics confined between coaxial cylinders

The onset of transient periodic dissipative structures (TPDS) is studied us ing the linear perturbation approximation when a sufficiently strong magnet ic field (B) is impressed on the uniformly aligned director (n(0)) of a nem atic confined to the annular space between two coaxial cylinders of radii R -2 and R-1 (R-2 > R-1). Only TPDS with axial or azimuthal periodicity is co nsidered. An approximate expression for the magnetic body force density is employed. The solutions mainly concern rigid anchoring. When n(0) is along the common axis, a radial field or an azimuthal field causes TPDS with peri odicity along the axis when the calamitic nematic has positive diamagnetic anisotropy (c(A) > 0); an axial field has a similar effect when c(A) < 0. T he dependence of the rise time as wed as the periodicity wavevector are stu died as functions of the applied field strength and the ratio of the radii (R-21 = R-2/R-1). A weakening of director anchoring has a deleterious effec t on the formation of TPDS. When n(0) is azimuthal and chi(A) > 0 a radial or an axial field may induce TPDS having an azimuthal periodicity wavevecto r which is an integer and related to the number of domains; continuous chan ges in control Variables cause discontinuous changes in the wavevector. Usi ng hypothetical material parameters, it is shown that an axial (or an azimu thal) field may induce TPDS with a continuously varying (or discontinuously varying) wavevector in a radially aligned discotic nematic having c(A) > 0 . If c(A) < 0, a radial field may induce TPDS with modulation along both th e axial and the azimuthal directions in a discotic nematic. When R-21 is cl ose to unity, the results of this work go over to those obtained for a flat sample.