POLYMERIC SALTS - STATIC AND DYNAMIC DEBYE-HUCKEL THEORY

We study polymeric salts formed by connecting ionic end groups by a so luble polymeric backbone: this can be done either by linking similarly charged ions (anions and cations) and then mixing positively charged and negatively charged chains or by linking oppositely charged ions. T his last case where the chains are globally neutral is of special inte rest: due to the connectivity constraint, the polymeric solution behav es as a dielectric at large length scales (in the absence of any small free ions) but it locally screens the electrostatic interactions such as a salt. In a suited range of end charge and chain length the stren gth of the macroscopic long-range interaction between test charges can be monitored by tuning the polymeric salt concentration. The relaxati on of thermal fluctuations in the solution has three eigenmodes: a fas t plasmon mode corresponding to the relaxation of charge fluctuations, and two modes independent of the strength of the electrostatic intera ction, one being the cooperative mode found in usual semidilute soluti ons. The plasmon mode resembles that in free salt solutions except tha t the chain connectivity restricts the size of the charge fluctuations to the coil size.