  We study suspensions of semi-flexible colloidal rods and biopolymers using an
Onsager-type second-virial functional for a segmented-chain model. For
suspensions of thin and thick fd virus particles we calculate phase diagrams in
quantitative agreement with experimental observations, and we find their
effective state-point dependent shape to be much shorter and thicker than the
actual shape. We also calculate the stretching of worm-like micelles in a host
fd virus solution, again finding agreement with experiments. For both systems,
our results show that the fd virus stiffness can play a key role in system
behavior.
