  Recent advances in Generalized Ensemble simulations and microcanonical
analysis allowed the investigation of structural transitions in polymer models
over a broad range of local bending and torsion strengths. It is reasonable to
argue that electrostatic interactions play a significant role in stabilizing
and mediating structural transitions in polymers. We propose a bead-spring
polymer model with randomly distributed charged monomers interacting via a
screened Coulomb potential. By combining the Replica Exchange Wang-Landau
(REWL) method with energy-dependent monomer updates, we constructed the
hyperphase diagram as a function of temperature ($T$) and charged monomer
concentration ($\eta$). The coil-globule and globular-solid transitions are
respectively second and first order for the entire concentration range.
However, above a concentration threshold of $\eta=80\%$, electrostatic
repulsion hinders the formation of solid and liquid globules, and the interplay
between enthalpic and entropic interactions leads to the formation of liquid
pearl-necklace ad solid helical structures. The probability distribution,
$P(E,T)$, indicates that at high $\eta$, the pearl-necklace liquid phase
freezes into a stable solid helix-like structure with a free energy barrier
higher than the freezing globule transition at low $\eta$.
