Homeotropic and planar structures in liquid-crystalline polymer brushes

A theory of polymer systems composed of grafted macromolecules with mesogenic units in the backbone (anisotropic brushes) is formulated within the framework of the mean-field approximation and analyzed using a numerical self-consistent field method. It is shown that two different liquid-crystalline (LC) states, homeotropic and planar, may exist in anisotropic polymer brushes. The free energy of a brush in the homeotropic LC state is always lower compared to that in the planar LC state. However, the results of numerical calculations indicate that both states may be realized when the anisotropic interaction energy of the system increases (on cooling). It is demonstrated that both surfaces of the brush play an important role in establishing of a particular LC state.