The Overlap Concentration in Strong Polyelectrolytes

Understanding strong polyelectrolytes in solution is a major challenge for theory. We have simulated a strong polyelectrolyte in a salt free solution for monomer numbers N =10 to 1600. We calculated the overlap concentration c^* and find that c^*scales as N ^-2.5. Morover, not until very large N ≥ 800 does the end-to-end distance at c^* approach the infinite dilution limit. The chains at large N are fully stretched at c^*, while at small N substantial stretching occurs below c^*. For large N the chains are also rodlike in that the form factor at c^* is almost that of a straight line for lengths corresponding from a few bond lengths to the end-to-end distance.