Construction of photo-responsive micelles from azobenzene-modified hyperbranched polyphosphates and study of their reversible self-assembly and disassembly behaviours

Photo-responsive micelles with reversible self-assembly and disassembly behaviours were constructed via the supramolecular host–guest interaction of β-cyclodextrin (β-CD) and an amphiphilic azobenzene-containing hyperbranched polymer (denoted HPHEEP-Azo). The polymer was prepared through the carboxylation of hydroxyl groups in hyperbranched polyphosphate (HPHEEP-OH) with succinic anhydride and the subsequent esterification reaction with 4-hydroxyazobenzene. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements reveal that HPHEEP-Azo can self-assemble into spherical micelles with an average diameter of 169.9 nm in aqueous solution. The critical micelle concentration (CMC) of the micelles is 0.013 mg mL−1. After addition of β-CD into the micellar solution, the micelles dissociated gradually upon increasing the addition amount of β-CD. Irradiation experiments show that reversible self-assembly and disassembly behaviours can be controlled by irradiating with UV and visible light. These photo-responsive micelles self-assembled from hyperbranched polymers might have great potential in various practical applications such as controlled drug release.