Fast\nIR-Actuated Shape-Memory Polymers Using in Situ Silver Nanoparticle-Grafted\nCellulose Nanocrystals

Abstract

In\nrecent years, shape-memory polymers (SMPs) have gained a key position\nin the realm of actuating applications from daily life products to\nbiomedical and aeronautic devices. Most of these SMPs rely mainly\non shape changes upon direct heat exposure or after stimulus conversion\n(e.g., magnetic field and light) to heat, but this concept remains\nsignificantly limited when both remote control and fine actuation\nare demanded. In the present study, we propose to design plasmonic\nsilver nanoparticles (AgNPs) grafted onto cellulose nanocrystals (CNCs)\nas an efficient plasmonic system for fast and remote actuation. Such\nCNC-<i>g</i>-AgNPs “nanorod-like” structures\nthereby allowed for a long-distance and strong coupling plasmonic\neffect between the AgNPs along the CNC axis, thus ensuring a fast\nphotothermal shape-recovery effect upon IR light illumination. To\ndemonstrate the fast and remote actuation promoted by these structures,\nwe incorporated them at low loading (1 wt %) into poly­(ε-caprolactone)\n(PCL)-based networks with shape-memory properties. These polymer matrix\nnetworks were practically designed from biocompatible PCL oligomers\nend-functionalized with maleimide and furan moieties in the melt on\nthe basis of thermoreversible Diels–Alder reactions. The as-produced\nmaterials could find application in the realm of soft robotics for\nremote object transportation or as smart biomaterials such as self-tightening\nknots with antibacterial properties related to the presence of the\nAgNPs.