Nanodiamond-grafted hyperbranched polymers anchored with carbon nanotubes: Mechanical, thermal, and photothermal shape-recovery properties

Nanodiamond-grafted hyperbranched polyurethanes (HPU-g-NDs) with various nanodiamond (ND) loadings were synthesized and composites with multi-walled carbon nanotubes (MWNTs) were prepared. The HPU-g-ND/MWNT composites showed significantly improved mechanical, thermal, and photothermal shape-recovery properties, compared to the HPU-g-NDs. Scanning electron microscopy of fractured surfaces revealed that the HPU-g-NDs are highly compatible with the polymer matrix as well as the highly dispersed MWNTs. The mechanical properties of the HPU-g-NDs were profoundly enhanced by the addition of MWNTs. The breaking stress and modulus of the HPU-g-ND (1 wt% ND) composite were enhanced by 29% and 42%, respectively, with the incorporation of only 1 wt% MWNTs. An exceptional increase in thermal stability, of about 60 °C at a weight loss of 50%, was observed for HPU-g-ND at 1 wt% ND, compared with that of pure HPU; this composite also exhibited better shape recovery and faster actuation behavior during laser-driven photothermal actuation.