Polyampholyte solutions between charged surfaces: Debye–Huckel theory

We calculate the interaction between two identically charged surfaces immersed in a polyampholyte solution in the framework of the linear response approximation. In the case of the randomly charged polyampholyte with equal fractions of positively f+ and negatively f− charged groups the interaction between charged surfaces is similar to that in electrolyte solutions. The screening of the surface potential in the linear response approximation is due to the charge redistribution on the length scales of the polymer coils without the excess of the polymers. In the solution of asymmetric polyampholytes (f+≠f−) the charge density fluctuations result in additional attractive interactions linearly proportional to the charge asymmetry.