Photoresponsive Rotaxane-Branched Dendrimers: From Nanoscale Dimension Modulation to Macroscopic Soft Actuators

Aiming at the construction of novel soft actuators throughtheamplified motions of molecular machines at the nanoscale, the designand synthesis of a new family of photoresponsive rotaxane-brancheddendrimers through an efficient controllable divergent approach wassuccessfully realized for the first time. In the third-generationrotaxane-branched dendrimers, up to 21 azobenzene-based rotaxane unitslocated at each branch, thus making them the first successful synthesisof light-control integrated artificial molecular machines. Notably,upon alternative irradiation with UV and visible light, photoisomerizationof the azobenzene stoppers leads to the collective and amplified motionsof the precisely arranged rotaxane units, resulting in controllableand reversible dimension modulation of the integrating photoresponsiverotaxane-branched dendrimers in solution. Moreover, novel macroscopicsoft actuators were further constructed based on these photoresponsiverotaxane-branched dendrimers, which revealed fast shape transformationbehaviors with an actuating speed up to 21.2 & PLUSMN; 0.2 & DEG; s(-1) upon ultraviolet irradiation. More importantly, theresultant soft actuators could produce mechanical work upon lightcontrol that has been further successfully employed for weight-liftingand cargo transporting, thus laying the foundation toward the constructionof novel smart materials that can perform programmed events.

Automated summary

A new family of photoresponsive rotaxane-branched dendrimers was successfully designed and synthesized for the construction of novel soft actuators. The precisely arranged rotaxane units can undergo collective and amplified motions upon alternate irradiation with UV and visible light, enabling controllable and reversible dimension modulation. These photoresponsive dendrimers were further utilized to construct macroscopic soft actuators that exhibit fast shape transformation behaviors and can perform weight-lifting and cargo transporting upon light control.