Two-step synthesis of polystyrene sulfonate based copolymers bearing pendant primary amines

Polyelectrolytes are macromolecular building blocks which find numerous applications in the design of colloids, interfaces, gels and membranes. Herein, new functional polyelectrolytes copolymers bearing pendant primary amines have been synthesized through the free radical copolymerization of sodium p-styrene sulfonate (SS) and acrylamide (AAm) or chloromethylstyrene (CMS) followed by a post-polymerization modification. The first strategy relies on the use of the Hofmann reaction to convert polystyrene sulfonate-polyacrylamide (P(SS-co-AAm)) copolymers into polystyrene sulfonate-polyvinylamine (P(SS-co-VA)) copolymers. The second route includes the N-alkylation of polystyrene sulfonate-polychloromethylstyrene (P(SS-co-CMS)) copolymers with 1,8-diamino-3,6-dioxaoctane (DADO). It was observed that the chemical modification of P(SS-co-AAm) copolymers of different composition through the Hofmann reaction was effective but lead to some side reactions. In addition, P(SS-co-CMS) copolymers of several composition were prepared in anhydrous DMSO to prevent the early hydrolysis of the CMS units, and were quantitatively post-modified at RT with an excess of DADO. The resulting copolymers were soluble in both water and DMSO, and preliminary experiments on their properties evidenced both the reactivity of their amino group toward reductive amination (either performed with propanal or onto an oxidized nanocellulose), and their polyampholyte behavior at pH below the amine pKa.