Loop-stabilized BAB triblock copolymer morphologies by PISA in water

Abstract

A straightforward strategy to synthesize loop-stabilized particles in water via PISA is developed. These particular structures can in theory be obtained through the synthesis of amphiphilic BAB triblock copolymers, starting from a hydrophilic middle block A, which is chain extended in an aqueous PISA process with two hydrophobic external blocks B. For this purpose, symmetrical bifunctional poly(N,N-dimethylacrylamide) macroRAFT agents with a central benzoic acid group and an alkyl chain as the Z group are used in the aqueous dispersion polymerization of diacetone acrylamide. For the first time, stable BAB flower-like particles are formed via PISA in pure water. It is shown that the colloidal stability and the resulting particle morphology (spheres, worms, vesicles) strongly depend on the degree of ionization of the central charge in the stabilizer loop, and thus on the pH at which PISA is performed. Moreover, the influence of the length of the alkyl Z group (dodecyl and butyl alkyl chains) on the colloidal stability is studied.