Interpolyelectrolyte Complexation in Chloroform

Abstract

Interpolyelectrolyte complexes (IPECs) were formed in chloroform from complementary polyelectrolyte-surfactant complexes (PESCs), i.e., linear polyelectrolytes whose counterions were substituted by surfactants to dissolve them in the low-polarity organic solvent. The interaction between such complementary PESCs was followed by turbidimetry, (1)H NMR, and dynamic light scattering. The experimental results, together with those from transmission electron microscopy and scanning force microscopy, provide evidence on the formation IPECs in the system. This process is apparently driven by the entropically favorable release of the pairs of the oppositely charged surfactant ions. If the mixing base-molar ratio between the complementary PESCs, Z, is below a certain threshold value, their chloroform mixtures are colloidally stable, containing relatively large aggregates. These aggregates are attributed to particles of the formed IPECs stabilized by the fragments of the excess polymeric component. Otherwise, the mixtures of the PESCs undergo phase separation (most pronounced at Z = 1) with the formation of an insoluble top phase (attributed to insoluble IPEC) and a clear bottom phase enriched with the surfactant counterions. Electron and scanning force micrographs indicate a rather broad size distribution of the soluble macromolecular coassemblies with a close to spherical shape.