Ionic liquid-modified TiO 2 nanoparticle-filled polyurethane as a new electro-responsive elastomer with controlled modulus and actuation strain by an electric field

Abstract

Abstract A new type of electro-responsive elastomer was prepared using polyurethane (PU) as the matrix and ionic liquid (IL)-modified TiO2 nanoparticles (TiO2-IL) as the active dispersed phase. The nanoparticles with different surface chemical structures (TiO2-IL: modified by IL only; TiO2-IL-AA: dual-modified by IL and acetic acid) were added in the second chain extension process and fixed by the solidified PU chains. The structures of the elastomers were analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and small-angle X-ray scattering (SAXS) to confirm the interaction between the nanoparticles and the soft and hard segments of PU. Rheological analysis was conducted under a controlled electric field, indicating that the PU-based elastomers showed electric field-improved modulus and the elastomer containing 20 wt% TiO2-IL nanoparticles exhibited the highest electrorheological (ER) efficiency of 247% at 3.0 kV/mm. Comparing the ER effects of the two types of nanoparticles, it was found that the TiO2-IL nanoparticles induced a stronger interfacial polarization effect and resulted in a higher ER effect than the TiO2-IL-AA nanoparticles. In addition, the PU-based elastomers containing TiO2-IL nanoparticles presented a significant electrostriction effect. The highest deformation in the thickness up to 14% occurs in the TiO2-IL-20wt% elastomer; however, the elastomers containing TiO2-IL-AA nanoparticles showed negligible actuation thickness strain, this might be related to the loose nature of TiO2-IL-AA nanoparticles. This research indicated that both electric filed-controlled modulus/rigidity and electric field-actuated deformation can be obtained in one system: the PU-based elastomer containing TiO2-IL nanoparticles, indicating its great potential in dual or multi-functional actuators.