Complex formation between poly(4-vinylpyridinium chloride) and poly[sodium(2-acrylamido-2-methyl propane sulfonate)] in dilute aqueous solution

Polyelectrolyte complexes (PEG) have been formed by mixing dilute aqueous solutions of the oppositely charged polyelectrolytes poly[sodium(2-acrylamido-2-methyl propane sulfonate)] (PAMPSNa) and poly(4-vinylpyridinium chloride) (PVPHCl). Over the entire range of feed compositions examined, a compact precipitate resulted. For many feed compositions, gravimetric analysis of the complex coupled with ultraviolet analysis of supernatant liquids demonstrated departures from stoichiometry. It was established that the composition of the complex was dependent upon the order of mixing: when PVPHCl was added to PAMPSNa, complexes contained approximately equimolar quantities of each precursor, whereas the complex comprised a significantly greater ratio of polycationic to polyanionic units when the order of addition was reversed. PEC formation in the presence of added salts was investigated also. Non-reacting solutions having a total polymer concentration of 12.3 gdm(-3) could be prepared in ca. 1.8 molal aqueous solutions of NaCl, NaBr and LiBr, but at lower salt concentrations PEC were formed due to insufficient shielding of ionic charges. Analysis of PVPHCl, PAMPSNa and PEC via differential scanning calorimetry and nuclear magnetic resonance spectroscopy established glass transition temperatures for the precursors only. It was concluded that glass transition temperatures for the complexes could not be detected due to the high density of ionic crosslinking.