Nitroxide-mediated copolymerization of methacrylic acid with sodium 4-styrene sulfonate: towards new water-soluble macroalkoxyamines for the synthesis of amphiphilic block copolymers and nanoparticles

The SG1-mediated copolymerization of methacrylic acid (MAA) and 4-styrene sulfonate (SS) was studied in dimethylsulfoxide solution at 76 °C, first, to determine the reactivity ratios in such conditions and second, to check the living character of the reaction at low molar fraction of SS. The reactivity ratios in the terminal model were rMAA = 0.44 and rSS = 1.34 indicating a favored incorporation of SS at the beginning of the copolymerization. All characteristics of a controlled/living system were observed, in good agreement with an efficient deactivation of the propagating radicals by the nitroxide SG1, via probable formation of an SS terminal subunit-based alkoxyamine. The method was shown to be particularly well-suited for the design of living polymers intended to be used as hydrophilic macroinitiators for the synthesis of amphiphilic block copolymers. This was demonstrated in both solution polymerization and ab initio, batch emulsion polymerization. The latter process allowed well-defined block copolymer nanoparticles to be formed at low temperature, in a single step, by simultaneous chain growth and self-assembling.