<正> Semi-rigid liquid crystal polymer is a class of liquid crystal polymers different from long rigidrod liquid crystal polymer to which the well-known Onsager and Flory theories are applied. Inthis paper

three statistical models for the semi-rigid nematic polymer were addressed. They arethe elastically jointed rod model

worm-like chain model

and non--homogeneous chain model.The nematic-isotropic transition temperature was examined. The pseudo-second transition tem-perature is expressed analytically. Comparisons with the experiments were made and the agree-ments were found.