Copolymerization of a cationic double-charged monomer and electrochemical properties of the copolymers

The free radical copolymerization of 1,3-bis(N,N,N-trimethylammonium)-2-propylmethacrylate dichloride (di-M) with acryloyloxyethyltrimethylammonium chloride (Q), diallyldimethylammonium chloride (DADMAC), and acrylamide (A) yielded novel polyelectrolytes and allowed for assessing the influence of the charge density and charge location on the monomer reactivity. Copolymerizing di-M and Q, two monomers with comparable chemical structure but differing by factor two in the number of charges, the reactivity of Q was higher than the reactivity of di-M. However, the difference diminished with increasing ionic strength. Despite 4-fold less cationic charge per monomer unit length, the reactivity of DADMAC was much lower than the reactivity of di-M. This clearly demonstrates the dominating influence of the location of the growing radical. The difference of the reactivity ratios for di-M/A was less than for di-M/Q. At low di-M fraction in the di-M/A monomer feed, di-M was even preferred. Decreasing intrinsic viscosity with increasing di-M fraction in the di-M/A monomer feed confirmed the electrostatic influence on the copolymer chain propagation. The counterion activity correlates well with the linear average charge density. However, deviation from theoretical values suggests the impact of the charge distribution.