A novel class of the liquid crystal polymers with mesogens laterally attached to flexible main chain backbones has been synthesized recently by us. While the flexible backbones tend to take configuration of maximum entropy the mesogenic side groups tend to orientate because of the anisotropie soft dispersion forces. A mean field theory is presented to describe the competition between these two trends which makes it possible for this class of polymers to show anisotropic (liquid crystal) phase within certain temperature range where the polymer main chains and the side chain mesogens will take approximately parellel arrangement

which is different from the mormal side chain liquid crystal polumers.The temperature range of the liquid crystal phase

its ordering and phase transition all depend on the flexibility of the backbone

the strength of the anisotropic forces of the side groups and the hinge elasticity.The results show that the liquid crystalisotropic phase transition is of the first order.The phase diagram

i.e.the dependence of the transition temperature on the structure of the polymers is also given.