Abstract
By suitable assignment of parameters such as persistence length and chain diameter it is possible to obtain quantitative agreement between the critical polymer volume fraction (v'2) measured for poly(n-hexylisocyanate) in toluene and calculated using the Khokhlov-Semenov and Odijk elaboration of Onsager theory. While the performance of the KSO theory with the most rigid chains is a satisfactory one, the above result is not of general validity and (v'2)theor/(v'2)exp is larger than unity for a variety of more flexible mesogens. Possible reasons for the discrepancy are indicated.