Reversible Photocontrolled Swelling‐Shrinking Behavior of Micron Vesicles Self‐Assembled from Azopyridine‐Containing Diblock Copolymer

Poly( N ‐isopropylacrylamide)‐ block ‐poly{6‐[4‐(4‐pyridyazo)phenoxy] hexylmethacrylate} (PNIPAM‐ b ‐PAzPy) was synthesized by successive reversible addition‐fragmentation chain transfer (RAFT) polymerization. In a water/tetrahydrofuran (H 2 O/THF) mixture, amphiphilic PNIPAM‐ b ‐PAzPy self‐assembles into giant micro‐vesicles. Upon alternate ultraviolet (UV) and visible light irradiation, obvious reversible swelling‐shrinking of the vesicles was observed directly under an optical microscope. The maximum percentage increase in volume, caused by the UV light, reached 17%. Moreover, the swelling could be adjusted using the UV light power density. The derivation of this effect is due to photoinduced reversible isomerization of azopyridine units in the vesicles. magnified image