Polyelectrolyte gels in poor solvent: Elastic moduli

We study theoretically using scaling arguments the behavior of polyelectrol yte gels in poor solvents. Following the classical picture of Katchalsky, o ur approach is based on single-chain elasticity but it accounts for the rec ently proposed pearl necklace structure of polyelectrolytes in poor solvent s. The elasticity both of gels at swelling equilibrium and of partially swo llen gels is studied when parameters such as the ionic strength or the frac tion of charged monomers are varied. Our theory could be useful to interpre t recent experiments performed in Strasbourg that show that if identical ge l samples are swollen to the same extent at different pH the sample with th e highest charge has the lowest shear modulus.