  Thermoreversible sol-gel transitions in solutions of rod-like associating
polymers are analyzed by computer simulations and by mean field models. The
sol-gel transition is determined by the divergence of the cluster weight
average. The analytically determined sol-gel transition is in good agreement
with the simulation results. At low temperatures we observe a peak in the heat
capacity, which maximum is associated with the precipitation transition. The
gelation transition is sensitive to the number of associating groups per rod
but nearly insensitive to the spatial distribution of associating groups around
the rod. The precipitation is strongly dependent on both the number and
distribution of associating groups per rod. We find negligible nematic
orientational order at the gelation and precipitation transitions.
