A supramolecular assembly of cross-linked azobenzene/polymers for a high-performance light-driven actuator

Light-driven flexible actuators based on a photo-responsive polymer draw much attention due to their great ability for rapid and reversible light-to-work transduction based on a large deformation. An azobenzene chromophore with disulfonic groups (AAZO) was noncovalently grafted on the side-chain of a cationic polymer, poly(diallyldimethylammonium chloride) (PDAC), by electrostatic interaction in a specific weight ratio. A supramolecular assembly of cross-linked AAZO/PDAC showed a reversible isomerization on irradiation by UV light followed by a reversion with a good cycling stability for 50 cycles. Light-driven actuators based on the AAZO/PDAC film exhibited a large deformation by rolling-up into a tube with double walls even when the light was off, along with a spontaneous shape recovery. This photomechanical deformation arose from different rates and degrees of structural transformation of AAZO/PDAC between the front (facing UV light) and back side with the segmental motion of polymers.