STRUCTURE FACTOR OF A SEMIDILUTE SOLUTION OF POLYDISPERSE RODLIKE MACROMOLECULES

The static structure factor of a semidilute solution of polydisperse rodlike macromolecules interacting via a hard core repulsion is calculated in the second virial approximation. A suitable substitution reduces the governing set of coupled integral equations to a single integral equation, which is attacked analytically by applying a variational principle. It is shown that the resulting expression for the structure factor is thermodynamically consistent. By way of example the structure factor of a bidisperse solution of rods is discussed and the marked effect of very small amounts of the higher molecular weight species demonstrated.