Functionalized carbon nanotubes based thermo-responsive shape memory blends with enhanced mechanical properties for potential robotics applications

A two-step approach was used to synthesize a thermo-responsive polyurethane and its blends with amino-functionalized-polystyrene (PS) and multiwall carbon nanotubes (MWCNTs) aiming at enhanced mechanical, thermal and shape memory properties. The synthesis of novel shape-memory polyurethane was confirmed by FTIR spectroscopy. SEM analysis of samples revealed excellent interfacial interaction due to chemical and physical interlinking between both polymers (PU synthesized and polystyrene functionalized) and functionalized multiwall carbon nanotubes (FMWCNTs) filler. The significant improvement in mechanical and thermal properties was observed for synthesized blends (PU/modified PS) as the filler content increased. The mechanical properties of PU/modified-PS blend having 3% loading amount of FMWCNTs were enhanced from 28.6 to 59.3 MPa as compared to those of neat PU. Due to proper fabrication and strong interfacial interaction, enhancement in thermal properties was also evident from the results with increasing filler loading amount. A sharp decrease in thermal, mechanical and recovery properties was also evident due to agglomerates net-points formation when loading amount of carbon filler increased from a certain level. Almost 100% shape recoveries were achieved for all samples, but the recovery durations of the samples were different. Modified-PS and FMWCNTs with PU formed three-dimensional interlocked networks which provided excellent mechanical strength, thermal stabilities and efficient shape recovery to the synthesized blends. Shape recovery response time of blends and nanocomposite was also found to decrease almost half of that of the pristine PU (less than 37 s for blends). Enhanced thermal stabilities, tensile properties, smaller shape recovery time, almost 100% shape recovery capabilities and sustainability, all factors favor the potential use of these blended composite materials in robotics, aeronautics, medical devices and high-performance materials in auto-industry.