Physicochemical and microstructural study of polyelectrolyte complexes obtained from carboxymethylcellulose sodium salt and quaternized poly(4-vinylpyridine)

This study investigates the complexation of long-chain carboxymethylcellulose sodium salt (NaCMC) with short-chain quaternized poly(4-vinylpyridine) (QP4VP). The novelty of this work lies in how the pH-dependent behavior of the polysaccharide derivative influences its conformation, which, in turn, impacts the polyelectrolyte complexes (PECs) formed. The study uses the polyanion NaCMC below its critical overlap concentration (C * = 0.2 wt%), ensuring the dominance of NaCMC – QP4VP interactions over NaCMC self-associations to yield soluble complexes. Complexation occurs through electrostatic interactions between carboxylate groups (COO¯) and pyridinium sites (4VPH+), along with hydrogen bonding, as validated by UV-visible spectroscopy, conductivity, and pH measurements. The manuscript also discusses the possibilities of interactions between the functional groups of both polyions. These interactions govern the appearance of insoluble zones of complexed segments and soluble zones of non-complexed segments within the material. Transmittance at 500 nm and zeta potential measurements confirm these zones. Those possibilities change based on the pH of NaCMC, which controls the ratio of COOH/COO¯ groups along the NaCMC chains. SEM imaging reveals a 3D porous network with features ranging from 175 nm to 23 µm, and TGA quantifies the contributions of each polyelectrolyte in the PEC.