A variational principle for liquid crystals subject to the thermal and elec
tromagnetic interactions is proposed in order to obtain the complete system
of field equations. The ideas suggested by Natanson and Sedov are applied.
Problems concerning the description of dissipative processes are discussed
. The polynomial form of the nonequilibrium constitutive equations of nemat
ic liquid crystals in the Lagrange description is considered. (C) 1999 Else
vier Science Ltd. All rights reserved.