Preparation of azobenzene-containing amphiphilic diblock copolymers for light-responsive micellar aggregates

Diblock copolymers composed of a side-chain liquid crystalline azobenzene-containing polymethacrylate and poly(tert-butyl acrylate) (PAzoMA-b-PtBA) were prepared using atom-transfer radical polymerization (ATRP). After subsequent selective hydrolysis of PtBA yielding poly(acrylic acid) (PAA), amphiphilic diblock copolymers of PAzoMA-b-PAA were obtained. Aggregation of either PAzoMA or PAA block occurs in solvents selective for one of the blocks. Adding water into dioxane solution of PAzoMA-b-PAA forms micellar aggregates due to the hydrophobic PAzoMA block. Under alternating UV and visible light illumination, reversible changes in micellar aggregates, for both core-shell micelles and vesicles, took place as a result of the reversible trans-cis photoisomerization of azobenzene mesogens in PAzoMA.