Sphere to disk transformation of micro-particle composed of azobenzene-containing amphiphilic diblock copolymers under irradiation at 436 nm

Diblock copolymer composed of azobenzene-containing polyacrylate and poly(acrylic acid) (PAzoM-b-PAA) was prepared using reversible addition–fragmentation chain transfer (RAFT) radical polymerization, which was found to form micro-particles through self-assembly. Under irradiation of light at 436 nm sphere to disk transformation of the micron-particle was observed in situ through an optical microscope. Detailed spectral analysis showed that a disruption of H-aggregate of azobenzene units had taken place during the transformation, from which it is realized that possible driving force of the transformation comes from the photoinduced disruption of H-aggregates within the micro-particles.