Mesophase Structure‐Enabled Electrostrictive Property in Nylon‐12‐Based Poly(ether‐block‐amide) Copolymers

Abstract

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.

Origins of Electrostriction in Poly(vinylidene fluoride)-Based Ferroelectric Polymers

“…Simultaneous D –E and S 1 – E loop measurements were conducted using the Radiant Premiere II FE tester, as described in a recent report . The applied voltage had a bipolar sinusoidal waveform with a frequency of 2 Hz.…”

“…Simultaneous D−E and S 1 −E loop measurements were conducted using the Radiant Premiere II FE tester, as described in a recent report. 29 The applied voltage had a bipolar sinusoidal waveform with a frequency of 2 Hz. This frequency was chosen because higher frequencies would reduce the strain value and lower frequencies The metalized film samples were immersed in silicone oil to avoid corona discharge in air.…”

Effect of Dipole Mobility in Secondary Crystals on Piezoelectricity of a Poly(vinylidene fluoride-co-trifluoroethylene) 52/48 mol % Random Copolymer with an Extended-Chain Crystal Structure

“…Simultaneous electric displacement–electric field ( D – E ) and transverse strain–electric field ( S 1 – E ) loops were measured using a Premiere II ferroelectric tester (Radiant Technologies, Inc., Albuquerque, NM) with a Trek 10/10B-HS high-voltage amplifier (0–10 kV AC, Trek, Inc., Lockport, NY), as described in previous reports. − The applied voltage had a bipolar sinusoidal waveform at 1 Hz. The film samples were coated with Au electrodes on both sides with an overlapping area of 8 × 3 mm 2 .…”

“…The final electric displacement was obtained by subtracting the stray capacitance and AC electronic conduction from the raw data. The transverse strain, S 1 , of the film samples (initial length of 8 mm) was measured using a home-built fixture connected to a photonic sensor MTI 2100 (MTI Instruments, Inc., Albany, NY), following the literature reports. − At high temperatures (>40 °C), significant AC electronic conduction was observed in the D – E loops for copolymer films with a large electrode area (24 mm 2 ). To solve this issue, separate D – E loop measurements were performed on samples with a small electrode area (7.06 mm 2 ).…”

Structure and morphology of thermoplastic polyamide 6 elastomers with different soft segment content and their foaming behavior using supercriticalCO2

“…At present, the most popular TPAEs for footwear foams is PA12 based TPAEs, named as PEBAX. [ 15 ] However, the high cost makes it only used for high‐end footwear. Therefore, the relatively inexpensive EVA and TPU were usually incorporated into TPAEs to prepare elastomer foams.…”