Development of a magnified sunlight responsive shape memory bio-composite: effects of titanium nitride (TiN) nanoparticles on a bio-based benzoxazine/epoxy copolymer†

This study uniquely explored the effects of loading titanium nitride (TiN) nanoparticles in a bio-based benzoxazine/epoxy copolymer on the shape memory performance of the resulting composite using normal and magnified sunlight irradiation stimuli scenarios. Additionally, the effects of loading the TiN nanoparticles in the copolymer on light absorbance capacity, thermal stability, visco-elastic properties, and tensile properties of the composites were analysed. Results reveal that the different loading amounts (1 to 7 wt%) of TiN dispersed well within the copolymer matrix and produced excellent composite samples (TiN-1(wt%), TiN-3(wt%), TiN-5(wt%), and TiN-7(wt%)). Interestingly, the obtained samples were found to exhibit improved light absorbance in the wavelength range of 200–900 nm, giving the samples greater sunlight absorbing capacity. Moreover, the thermal stability of the composites increases with an increase in the loading amount; for instance, the initial degradation temperature increased from 316 °C to 324 °C. Meanwhile, visco-elastic and tensile properties increased and reached the optimum for TiN-5(wt%), where 3.1 GPa and 10.4 MPa were recorded as storage modulus and tensile stress, respectively. Consequent to these improvements in the properties of the composites, the shape memory performance of the composites was positively impacted. For instance, average shape fixity ratio, shape recovery ratio, and recovery time of 95%, 96%, and 38 seconds, respectively, were achieved with TiN-7(wt%), which represents 19%, 17%, and 38% improvements, respectively, compared to when the neat copolymer (TiN-0(wt%)) was used using magnified sunlight irradiation stimulus. Overall, this finding provides the basis for the utilization of magnified sunlight irradiation stimulus to achieve excellent shape memory performance with TiN-filled polymer composites.