Polyelectrolyte complexation between cationic and anionic polyelectrolytes with complementary polymer-bound reactive groups of amine and acetoacetate: effect of mono- and divalent salts

Abstract

The copolymers of methacrylic acid with 0–50 % of 2-(methacryloyloxy)ethyl acetoacetate, and the copolymers of 2-(methacryloyloxy)ethyl trimethyl ammonium chloride with 0–50 % of 2-aminoethyl methacrylate were prepared by free radical polymerization in various solvents. The polyelectrolytes were characterized by potentiometric titration, NMR, viscometry and size exclusion chromatographic techniques. Polyelectrolyte complex formation between oppositely charged polyelectrolytes with polymer-bound (non)reactive polyelectrolytes was studied in the presence of NaCl and CaCl2 as a function of ionic strength. The physical nature and efficiency of polyelectrolyte complexes that form gels, liquid coacervates, or soluble complexes depend on variables such as ionic strength and charge ratio. The highest complexation efficiency was obtained when a 1:1 charge ratio was used. Liquid coacervates were obtained with high ionic strength NaCl. The inclusion of small amounts of CaCl2 led to drastic property changes in the polyelectrolyte complexes. The divalent calcium ion (Ca2+) displaced the poly[2-(methacryloyloxyethyl) trimethyl ammonium chloride] from the complexes and appeared as a new form of liquid coacervate in a range of ionic strength (50–200 mM CaCl2). The reactivity of the polyelectrolyte system was demonstrated by studying the formation of coacervate complexes. Herein, the feasibility of cross-linking of the resulting coacervate via complementary poly(methacrylic acid-co-2-(methacryloyloxy)ethyl acetoacetate)-bound acetoacetate groups with poly(2-(methacryloyloxy)ethyl trimethyl ammonium chloride-co-2-aminoethyl methacrylate)-bound amine groups is discussed in detail.