A facile synthesis of dynamic, shape-changing polymer particles

We herein report a new facile strategy to ellipsoidal block copolymer nanoparticles that exhibit a pH-triggered anistropic swelling profile. In a first step, elongated particles with an axially stacked lamellae structure are selectively prepared by utilizing functional surfactants to control the phase separation of symmetric polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) in dispersed droplets. In a second step, the dynamic shape change is realized by cross-linking the P2VP domains, thereby connecting glassy PS discs with pH-sensitive hydrogel actuators. Let surfactants do the work: Controlling the shape and morphology of polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) particles through the use of tailored, mixed surfactant systems allows for the facile and selective preparation of ellipsoidal nanoparticles. Cross-linking of the axially stacked P2VP lamellae domains allows the pH responsiveness of the 2VP moieties to be exploited with generation of unique shape- and structure-responsive particles.