Polysalt complexes of poly(crown ethers) and sodium carboxymethylcellulose

Insoluble polysalt complexes are formed on mixing aqueous solutions of poly(vinylbenzo‐18‐crown‐6) (P18C6) and sodium carboxymethylcellulose (CMC) in the presence of certain salts. Potassium salts are especially effective, converting the neutral P18C6 into a polycation which then interacts with sodium CMC. Nearly quantitative precipitation can be achieved at low KCl concentration (ca. 0.005M) for a crown/carboxylate ratio of approximately 5, while for 0.1–0.2M KCl the precipitation is close to completion at a crown/CMC ratio of about 2. The precipitates solubilize again on addition of water or concentrated KCl. Precipitation also occurs with CsCl but not with NaCl. Potentiometric measurements were carried out to determine the complex formation constant of the three alkali ions to P18C6. Their values can be used to rationalize the observed phenomena. Charge equivalence appears to play an important role in the formation of the polysalt complexes.