On the kinetics of the polymerization of some ammonium methacrylates with different alkyl chain lengths in aqueous solution

Methacryloyloxyalkyltrimethylammonium chlorides ( 1a–c ) with different alkyl chain lengths were synthesized and polymerized radically with 4,4′-azobis(4-cyanovalerianic acid) and K₂S₂O₈ as initiators. With K₂S₂O₈ as initiator, reaction orders of 0,5 and 1 with respect to initiator and monomer, were found. For the ionic monomers with longer alkyl chains the ratio of rate constants k_p(2fk_d/k_t)^0,5 was determined over a wide concentration range. It was found that with decreasing monomer concentration the ratio of rate constants increases, which is caused by a diminished termination rate because of an increased electrostatic repulsion of the ionic polymer radicals in dilute solution (increase of dissociation). Methacryloyloxyethyltrimethylammonium chloride ( 1a ) doesn't show this effect. This can be explained by the diminished effective charge of the ammonium group in the preferred gauche conformation of the molecule.