Conformations of polyampholytes

Polyampholytes are polymers composed of positive and negative charges randomly quenched along the chain. We examine configurations of such macromolecules by Monte Carlo simulations and analytical arguments. Polyampholytes with an overall constraint of charge neutrality are found to collapse into compact globules. Without such a constraint, on lowering temperature, the chain initially reduces its size and then becomes stretched due to a net charge imbalance. Experimental preparation conditions (water or organic solvent) determine if the polymer is overall neutral or randomly charged.