The self-assembly and photoresponsive properties of an amphiphilic azo random copolymer bearing branched azobenzene side chains (PMAPB6P-AA) are reported.The aggregates of PMAPB6P-AA in THF/H2O dispersion were obtained by slowly adding deionized water into a THF solution of the polymer to the water content of 80 vol%.Instead of quenching the aggregates with excess water to form solid colloidal spheres

the dispersion was diluted with a THF/H2O mixture (THF/H2O=1/4

V/V) and then THF in the medium was slowly removed through evaporation.The procedure could generate a series of hollow-structured aggregates with different sizes simply by adjusting the preparation conditions.The hollow aggregates were characterized by transmission electron microscopy (TEM)

scanning electron microscopy (SEM) and dynamic light scattering (DLS).Photoisomerization behavior of the azobenzene units was studied to detect the local environment surrounding the molecular probes in the hollow aggregates.Results showed that hollow aggregates possessed the non-spherical morphology at relatively high increasing rate of water content.The size (hydrodynamic diameter) of the hollow aggregates was determined by the polymer initial concentration in THF.The photoinduced isomerization rate and the photoisomerization degree of the hollow aggregates decreased with the increase of polymer initial concentration in THF.The vesicle-like aggregates with a thin shell were formed by diluting the polymer disperse at 23 vol% water content with THF/ H2O (THF/H2O=10/3

V/V) and slowly removing THF through evaporation.For the vesicle-like aggregates

photoinduced disaggregation was observed when irradiated with the 365 nm UV light.The understanding obtained from this study can be used to develop new functional materials from photoresponsive random copolymers.