Fast IR-Actuated Shape-Memory Polymers Using in Situ Silver Nanoparticle-Grafted Cellulose Nanocrystals

Abstract

In recent years, shape-memory polymers (SMPs) have gained a key position in the realm of actuating applications from daily life products to biomedical and aeronautic devices. Most of these SMPs rely mainly on shape changes upon direct heat exposure or after stimulus conversion (e.g., magnetic field and light) to heat, but this concept remains significantly limited when both remote control and fine actuation are demanded. In the present study, we propose to design plasmonic silver nanoparticles (AgNPs) grafted onto cellulose nanocrystals (CNCs) as an efficient plasmonic system for fast and remote actuation. Such CNC- g-AgNPs "nanorod-like" structures thereby allowed for a long-distance and strong coupling plasmonic effect between the AgNPs along the CNC axis, thus ensuring a fast photothermal shape-recovery effect upon IR light illumination. To demonstrate the fast and remote actuation promoted by these structures, we incorporated them at low loading (1 wt %) into poly(ε-caprolactone) (PCL)-based networks with shape-memory properties. These polymer matrix networks were practically designed from biocompatible PCL oligomers end-functionalized with maleimide and furan moieties in the melt on the basis of thermoreversible Diels-Alder reactions. The as-produced materials could find application in the realm of soft robotics for remote object transportation or as smart biomaterials such as self-tightening knots with antibacterial properties related to the presence of the AgNPs.

Shape‐Memory Polymers for Biomedical Applications

“…Additionally, modest shape recovery values of 90% were obtained. [ 90 ] Another antimicrobial shape‐memory polymer was reported by Zhang et al who used a diketopyrrolopyrrole‐based conjugated polymer as photothermal filler in a polycaprolactone‐ co ‐polyurethane matrix. Interestingly, the antibacterial effect of the polymer is only active upon irradiation with the near‐infrared light (808 nm) used for the recovery of the permanent shape, showing that their antibacterial effect is photothermally induced.…”

Light‐Responsive Shape‐Changing Polymers

“…Poly(ε‐Caprolactone) (PCL) : The photothermal effect has also been realized in shape‐memory polymers, such as semicrystalline biodegradable poly(ε‐caprolactone). For instance, Toncheva et al proposed plasmonic silver nanoparticles grafted onto cellulose nanocrystals as an efficient system for remote light‐induced actuation, which could be incorporated into PCL ( Figure a) . The photothermal effect upon irradiation with infrared (IR) light allowed the materials to return to their initial shape by melting the crystalline phases within the polymer, which released the stress stored within the temporary shape.…”

“…a) PCL films with/without incorporated silver nanoparticles grafted onto cellulose nanocrystals and their IR‐induced actuation for remote object transportation. Reproduced with permission . Copyright 2018, American Chemical Society.…”

“…The use of a photothermal light‐driven actuator material, based on silver nanoparticles grafted onto cellulose nanocrystals and incorporated into PCL polymer networks, for self‐tightening sutures with antibacterial properties was proposed by Toncheva et al As a proof‐of‐concept, samples were heated to a temperature close to the melting temperature of PCL, stretched at 100% deformation, and fixed in a knot‐like shape upon cooling. IR irradiation was applied for fast shape recovery, leading to the self‐tightening suture behavior with potential for wound closure applications.…”

Light‐induced dynamically tunable micropatterned surface for the regulation of the endothelial cell alignment

“…Near-infrared (NIR) light is suitable for in vivo biomedical applications because of the excellent tissue penetration [27]. Therefore, many efforts have been made to develop NIR-induced SMP composites based on the addition of photothermal fillers such as carbon nanotubes, graphene, and gold nanorods [28][29][30][31]. These SMP composites absorb NIR light and convert the optical energy into heat to realise the shape recovery of the SMP composites.…”