Phase changes of polyion complex between poly(methacrylic acid) and a polycation carrying charges in the chain backbone

The polyion complexes were obtained by mixing the aqueous solution of poly(methacrylic acid) and that of poly[( N,N,N′,N′ ‐tetramethyl‐ N‐p ‐xylylene)ethylenediammonium dichloride] ( 1 ). The forms of the polyion complex were observed as a homogeneous solution, a coacervate, or a precipitate under changing such conditions as the polyion concentration, pH, and the ionic strength. Especially, pH and the ionic strength affected the forms of the complex through the degree of dissociation of poly(methacrylic acid). The relations between these factors and the forms of the complex are shown as phase‐diagrams. The correlation among these factors is discussed, too.