Mechanism of Chain Collapse of Strongly Charged Polyelectrolytes

We perform extensive molecular dynamics simulations of a charged polymer in a good solvent in the regime where the chain is collapsed. We analyze the dependence of the gyration radius R-g on the reduced Bjerrum length l(B) and find two different regimes. In the first one, called a weak electrostatic regime, R-g similar to l(B)(-1/2), which is consistent only with the predictions of the counterion-fluctuation theory. In the second one, called a strong electrostatic regime, we find R-g similar to l(B)(-1/5). To explain the novel regime we modify the counterion-fluctuation theory.