Multiphase Structure and Electromechanical Behaviors of Aliphatic Polyurethane Elastomers

Abstract

Understanding the relationship between multiphase structure and electromechanical property of thermoplastic dielectric elastomers is significantly important in the developments of high-performance and novel dielectric elastomers. In this work, we fabricated a series of aliphatic polyurethane elastomers (PUEs) based on hydroxyl-terminated butadiene-acrylonitrile copolymer (HTBN), hexamethylene diisocyanate (HDI), and various lengths of linear aliphatic diols and investigated effect of their microstructure and morphology on dielectric and electromechanical properties. The FTIR, WAXS, SAXS, and viscoelastic AFM results showed that the PUEs existed in crystalline phase, hard domain (HD) and soft domain (SD) phases composed HD-rich region and few HDs and SD composted SD-rich region by crystallization and microphase separation. Also, the crystal morphology and crystallinity of PUEs are strongly influenced by the length of chain extender due to the chain extender adopting various conformations by hydrogen bonding. The mechanical and electric fields induced responses of segment motions in PUEs at below room temperature were relative to the constrained SS motions from HD-rich and SD-rich regions. The electric field induced strain of PUEs was actuated by both Maxwell stress and electrostriction effect, of which contribution of electrostriction effect was above 64% in total actuation strain. In addition, we found that the effect of electrostriction on the actuation strain played an important role in improving the actuation strain of PUEs at lower electric field. Our results showed that the dielectric and electromechanical properties of PUEs can be adjusted by controlling the crystallization and microphase separation.

Relationship between structure and dynamic mechanical properties of thermoplastic polyurethane elastomer containing bi‐soft segment

“…Since the hard domains (HDs) of TPUs are formed by ordered hydrogen bonded (Hbonded) hard segments, the CO groups of TPUs can be divided into four types based on the degree of hydrogen bonding. Those CO groups [28,29] include free CO, disordered H-bonded CO, ordered H-bonded CO, and ordered H-bonded CO in crystalline phase which are corresponding to bands at 1,730, 1,716, 1,704, and 1,690 cm −1 , respectively, as shown in Figure 2. The free CO groups are from SD, and the disordered H-bonded CO groups are from SD or the interphase between HD and SD.…”

Advanced dielectric elastomer based on optimized thermoplastic polyurethane–styrene ethylene butylene styrene blend: Experiment and simulation

“…A large variety of elastomers, including silicone rubbers, 7 acrylic elastomers, 8 and thermoplastic polyurethanes (TPU) 9 have been applied to assemble DEA. Among them, TPU is a promising candidate due to its relatively high permittivity, great breakdown strength, easy processing, good biocompatibility, and low cost 5,10,11 . While a key limitation for the practical application is the requirement for high driven electric field ( E ) (>100 kV mm −1 ), 4,12,13 which is due to its poor actuation strain at a low electric field.…”

Physical properties and dielectric behavior of the poly(urethane‐urea) based on o‐dianisidine and renewable cross‐linkers

“…DAN4 shows a more pronounced increase in dielectric losses from a much lower temperature (−25 C) due to the Tween 20 structure, which has fewer constraints in achieving dipole polarization. 42 F I G U R E 1 1 Arrhenius plots ln(τ max ) versus 1000/T for the β relaxation of the (a) linear and (b) cross-linked poly(urethane-urea) [Color figure can be viewed at wileyonlinelibrary.com] T A B L E 6 Arrhenius parameters: Activation energy, E a , and pre-exponential factor, τ 0 , for secondary γ and β relaxations Previous studies have shown that the introduction of small amounts of dipole moieties, such as that of aromatic groups, on the main chain of the polymer results in increase dielectric permittivity. 54 The presence on the polymer main chain of urethane groups, small amounts of aromatic groups as well as methoxy groups grafted on the aromatic group, all these confer high polarity which results in high dielectric capacitance, as shown by the results in Figure 6 (ε 0 = 7.6 at 1 Hz and ε 0 = 5 at 10 6 Hz, obtained at −25 C).…”

“…39,40 The electrical properties of polyurethanes and poly(urethane-urea) are important and are studied in order to obtain intelligent polymeric materials with electrical properties determined by the frequency and intensity of the applied electric field. 7,41 Previous results 42,43 have indicated that the dielectric constant and the dissipation factor of the polyurethanes are dependent both on the orientation of the dipole of the hard and soft segments, but also on their microstructure. Dielectric spectroscopy is used for the investigation of the molecular dynamics of the polyurethanes and poly(urethane-urea) with polar structure in very broad range of frequencies.…”