Chemical doping-assisted shape transformation of block copolymer particles

Shape-tunable block copolymer (BCP) particles have attracted significant attention due to their applications as smart materials. Herein, we report iodine (I₂)-mediated doping of polystyrene-block-polybutadiene (PS-b-PB) particles as a facile strategy to transform spherical BCP particles into nonspherical shaped particles. Upon introducing the I₂ molecules to internally phase-separated spherical PS-b-PB particles, I₂ selectively reacts with the double bonds in PB blocks while leaving the PS block unaffected. Monitoring the shape-transformation process reveals a gradual structural transition from spheres to oblates and ellipsoids as a function of reaction time, consistent with the increasing conversion of the double bonds into I₂-doped cation radicals. Consequently, the interfacial tension of I₂-doped PB blocks decreases, neutralizing the interfacial interaction of BCP and its surroundings, thereby restructuring the spherical particles into shape-anisotropic forms. Furthermore, the versatility of I₂-mediated shape transition is demonstrated by applying the same chemistry to polystyrene-block-poly(4-vinylpyridine) BCP particles. Finally, spheroidal particles doped with I₂ exhibit photothermal heating behavior, highlighting their potential application as photothermal agents.