STRUCTURE FORMATION IN DOPED DISCOTIC POLYMERS AND LOW MOLAR MASS MODEL SYSTEMS

Doping of low molar mass materials or polymers, possessing disc-like units, with electron acceptors leads to the stabilization of columnar discotic phases or even to the induction of such phases in compounds which either display a nematic discotic phase or only an amorphous phase in the absence of the electron acceptor. The induced columnar phase corresponds frequently to a hexagonally ordered one. We have observed, however, in addition the induction of new columnar phases such as the rectangularly ordered (D(ro)) and the columnar nematic phase (N(c)). The enhancement of the tendency towards the formation of columnar phases is a consequence of electron acceptor-electron donor complex formation. Using a model proposed by de Jeu to describe the induction of smectic phases by complex formation we are able to account qualitatively for the experimental findings.