Electrostrictive Energy Conversion of Polyurethane with Different Hard Segment Aggregations

Abstract

This work reported the electrostriction of polyurethane (PU) with different aggregations of hard segments (HS) controlled by dissimilar solvents: N,N-dimethylformamide (DMF) and a mixture of dimethyl sulfoxide and acetone denoted as DMSOA. By using atomic force microscopy and differential scanning calorimetry, the PU/DMSOA was observed to have larger HS domains and smoother surface when compared to those of the PU/DMF. The increase of HS domain formation led to the increase of transition temperature, enthalpy of transition, and dielectric constant (0.1 Hz). For the applied electric field below 4 MV/m, the PU/DMSOA had higher electric-field-induced strain and it was opposite otherwise. Dielectric constant and Young’s modulus for all the samples were measured. It was found that PU/DMF had less dielectric constant, leading to its lower electrostrictive coefficient at low frequency. At higher frequencies the electrostrictive coefficient was independent of the solvent type. Consequently, their figure of merit and power harvesting density were similar. However, the energy conversion was well exhibited for low frequency range and low electric field. The PU/DMSOA should, therefore, be promoted because of high vaporizing temperature of the DMSOA, good electrostriction for low frequency, and high induced strain for low applied electric field.

Deformation on segment-structure of electrostrictive polyurethane/polyaniline blends

“…Moreover, the film samples with NMP solvent were stiffer with DMF, which is in good agreement with T g and T m observations. As previously reported, the increase of HS domain formation leads to the increase of T g that may indicate how the hard domains restrict soft segment mobility [24]. As the glass transition temperature shift to higher position, the percentage of the soft segment being restricted by the induced HS domains.…”

“…In addition, the T m in NMP solvent was higher than the samples in DMF solvent. Consequently, the higher values of the T m indicated that the HS aggregations of the blend in NMP solvent were greater than the blend in DMF [24]. Fig.…”

“…However, beyond about 4 MV/m the electrostrictive strain became saturated. This is related to the saturation of dipole moments in heterogeneous PU matrix and the HS domain mobility [24]. Fig.…”

“…The NMP effectively induced the HS to aggregate during blend preparation [24,25]. The HS tend to aggregate and give ordered crystalline domains as shown in Fig.…”

Contribution of Electrostriction in Polyurethane/Polyaniline Blends

“…5. However when increased the external electrical field, the electrostrictive strain becomes saturated due to its saturation of dipole moment in heterogeneous PU matrix and HS domain mobility [7]. Meanwhile, the electric field-induced strain increased when increasing the content of PANI.…”