Nonstoichiometric Polyelectrolyte Complex of Carboxymethylcellulose and N-Methylated Poly(2-vinylpyridine): Formation of a Gel-Like Structure

The formation of polyelectrolyte complexes between carboxymethylcellulose and N-methylated poly(2-vinylpyridine), at a nonstoichiometric mixing ratio, was studied. Various methods, such as viscometry, turbidimetry, electrophoresis, and optical spectroscopy, were used to investigate the complexes with respect to their composition, structure, and stability in aqueous systems of different ionic strengths. A gel-like structure was proposed for the nonstoichiometric polyelectrolyte complexes. Two steps of complex formation—ionic bond formation followed by its rearrangement—were identified. The conformational change of the polyelectrolyte chains in the complexes, responsible for the slower and latter step, was followed by viscometry, and the results were interpreted on the basis of a model proposed for the kinetics of swelling of hydrogels. A similarity was found between the kinetics of diffusion of polymer segments responsible for the swelling of a macrogel of a nonionic polymer and the rearrangement of ionic bonds leading to the formation of a nonstoichiometric polyelectrolyte complex el. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2288–2295, 2003