Microphase separation in poor‐solvent polyelectrolyte solutions: Phase diagram

Microphase separation in solutions of weakly charged polyelectrolytes in poor solvents is studied in the weak segregation limit within the framework of the mean field approximation using a method first developed by Leibler. As a result a complete phase diagram of the solution near the critical point is obtained. The regions of the stability of the disordered, homogeneous phase and of body-centered cubic (bcc), triangular and lamellar microdomain structures, as well as the phase separation regions are determined. The most striking difference in comparison with the corresponding diagram for block-copolymer melts is the existence of broad phase separation regions even for monodisperse systems. As the quality of solvent becomes poorer, the triangular microdomain structure remains the most stable among microdomain phases of other symmetry.