Selectively actuated multi-shape memory effect of a polymer multicomposite
In this paper, a new type of multicomposite styrene-based shape memory polymer (SSMP) was fabricated. This new SSMP included three regions: a SSMP matrix filled with multiwalled carbon nanotubes (SSMP–CNT), a SSMP matrix filled with Fe3O4 nanoparticles (SSMP–Fe3O4), and a third neat SSMP region which is located between the two composite regions. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) results demonstrated that all the three SSMP materials possessed two well-separated transitions, which were subsequently used for the fixing/recovery of two temporary shapes (triple-shape memory effect) in each region. Furthermore, the unique selective actuation functionality of the multicomposite was demonstrated, based on the principle that Fe3O4 nanoparticles and CNT can selectively induce heat in a 30 kHz alternating magnetic field and 13.56 MHz radiofrequency, respectively. Therefore, well-controlled multiple shape recoveries of the multicomposite SSMP were achieved by applying selective stimuli. This proposed approach of selective actuations can be applied to other stimuli-responsive material systems to generate complex structures for target applications.