Tuning the morphology of amphiphilic copolymer aggregates by compound emulsifier via emulsion-solvent evaporation

A series of poly(4-vinylpyridine)-b-poly{6-[4-(4-butyloxyphenylazo)phenoxy]hexyl methacrylate} (P4VP-b-PAzoMA) were employed to fabricate aggregates via the emulsion-solvent evaporation method. The emulsion was stabilized by compound emulsifier composed of SDS and span60. By tuning the ratio of two emulsifiers, P4VP-b-PAzoMA could self-assemble into various morphologies including porous microspheres, tremella-like aggregates, bowl-like aggregates and wrinkled microspheres. The transformation of the morphologies could be ascribed to three major aspects: the stability of emulsified chloroform droplets, the permeation of water into chloroform and the dispersity of the interior water droplets with regard to different HLB values. Besides, the morphology could even be tuned by changing the block ratio and the concentration of P4VP-b-PAzoMA, and the HLB dependent morphology changing was also proved within other block ratio or different concentration. The study uncovers a convenient and effective technique to manipulate the morphology of amphiphilic copolymer aggregates.