Shape-memory poly(arylene ether ketone)s with tunable transition temperatures and their composite actuators capable of electric-triggered deformation

In this paper, a series of shape-memory poly(arylene ether ketone)s (PAKEs) with various flexible groups (i.e., carbolic bonds, ether, and ketone linkages) and entangled crystalline polymeric structures were synthesized by combining different bisphenol monomer (bisphenol A monomer and methyl hydroquinone monomer) proportions with a 4,4′-difluorobenzophenone monomer. The flexible parts and the entangled parts acted as a reversible phase and permanent phase, respectively. The prepared PAEK films exhibited excellent heat-triggered shape-memory behaviors with tunable glass transition temperatures (T_g) from 116 °C to 140.5 °C including an extremely high fixity ratio (over 98%), high recovery ratio (over 92%), and fast recovery rate (within 7.0 s). As increasing the content of the methyl hydroquinone monomer in the structural unit, the recovery ratio showed a downward trend, whereas the recovery time increased gradually. In addition, the electric-triggered shape-memory effect of the PAEK films was achieved via the introduction of carbon nanotubes (CNTs). Upon applying a voltage of 25 V, the recovery ratios of the composite films containing 10 wt% and 15 wt% CNTs were all over 80% (of 83.0% and 87.6%, respectively), indicating a great electric-triggered shape-memory behavior. The recovery ratio increased and the triggered voltage decreased as increasing the content of CNTs. The heat and electric dual-triggered shape-memory PAEK composites could be important smart materials possessing wide application prospects.