NEMATIC PHASE-TRANSITIONS OF FLEXIBLE SPHEROCYLINDRICAL MOLECULES

A torsionally flexible molecule is represented as a spherocylinder tha t undergoes fluctuations in either its cap radius (breathing mode) or its cylinder length (stretching mode). The free energy of the flexible spherocylinder is calculated in analogy with earlier work based on de nsity functional and Onsager theories of the isotropic-nematic transit ion. In the Landau-de Gennes limit of this theory, there are three ord er parameters, corresponding to the molecular alignment, molecular sha pe and an alignment-shape coupling. The effect of flexibility on the p rimary order parameter is addressed as well as the effect of alignment on molecular shape.