Discussion of the Flory theory

To overcome the contradiction, Flory and Ronca (1979) made the following improvement for the three-dimensional lattice 

It is more reasonable to adopt Equation 2.58 instead of Equation 2.28. 

It was pointed out that the approximation form in Equation 2.37 used for Zorient (valid only for high degrees of orientation) leads to the incorrect result that an isotropic phase can exist in a solution of rods in an external orienting field. 

Free energy resulting from the orientational distribution was precisely defined in the Onsager model (Equation 2.19) instead of Equation 2.35 

In this modified Flory model, the liquid crystal-isotropic transition of rods in a solution occurs at 

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