To search for alternative electrostrictive polymers and to understand the underlying mechanism, the structure‐ferroelectric/electrostrictive property relationship for nylon‐12‐based poly(ether‐b‐amide) multiblock copolymers (PEBAX) is investigated. Two PEBAX samples are studied, namely, P6333 and P7033 with 37 and 25 mol.% of soft poly(tetramethylene oxide) (PTMO) blocks, respectively. In both samples, poorly hydrogen‐bonded mesophase facilitates electric field‐induced ferroelectric switching. Meanwhile, the longitudinal electrostrictive strain (S1)–electric field (E) loops are obtained at 2 Hz. Different from conventional poly(vinylidene fluoride‐co‐trifluoroethylene) [P(VDF‐TrFE)]‐based terpolymers, uniaxially stretched nylon‐12‐based PEBAX samples exhibit negative S1, that is, shrinking rather than elongation in the longitudinal direction. This is attributed to the unique conformation transformation of nylon‐12 crystals during ferroelectric switching. Namely, at a zero electric field, crystalline nylon‐12 chains adopt a more or less antiparallel arrangement of amide groups. Upon high‐field poling, ferroelectric domains are enforced with more twisted chains adopting a parallel arrangement of amide groups. Meanwhile, extensional S1 is observed for P6333 at electric fields above 150 MV m−1. This is attributed to the elongation of the amorphous phases (i.e., amorphous nylon‐12 and PTMO). Therefore, competition between shrinking S1 from mesomorphic nylon‐12 crystals (i.e., nanoactuation) and elongational S1 from amorphous phases determines the ultimate electrostriction behavior in stretched PEBAX films.

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In this paper, a parallel plate structure for the magnetic capacitor applications is presented, which consists of hybrid materials of Fe3O4 nanoparticles with polydimethylsiloxane (PDMS) as the dielectric medium. By changing the nanoparticle sizes and concentrations in PDMS, the magnetic-capacitance effect of the designed structure is investigated, and some key factors which may affect the performances are studied. It can be concluded from the results that a clear magnetic-capacitance coupling effect is observed by putting the designed Fe3O4 nanoparticles and PDMS hybrid material in or out of a magnetic field. Meanwhile, as we increase the concentration of the nanoparticles, an increase of capacitance variation may be observed. If the nanoparticle sizes are bigger than the critical dimension of the super-paramagnetic effect, the capacitance variations is increased as the nanoparticle size increases.