First-order conformational transition of annealed polyelectrolytes in a poor solvent

We present Monte Carlo simulations on annealed polyelectrolytes in poor solvent. Increasing the chemical potential of the charges, which is equal to the p H of the solution except for a trivial additive constant, we find the first-order phase transition between a weakly charged globule and a highly charged extended chain predicted by theory. Starting from an elongated highly charged conformation and increasing the coupling strength u = λ B / b , the degree of stretching of the chain at first increases similarly to quenched polyelectrolytes. However, on reaching some upper threshold u *, the chain collapses back into a weakly charged state.