Ionic Liquid Cation Size-Dependent Electromechanical Response of Ionic Liquid/Poly(vinylidene fluoride)-Based Soft Actuators

Abstract

This work reports on the development of ionic liquid (IL)/poly(vinylidene fluoride) (PVDF) actuator composites. ILs sharing the same anion (bis-(trifluoromethylsulfonyl)imide, [TFSI] − ), and different cations belonging to the families of pyridinium, imidazolium, and ammonium ions, comprising an alkyl side chains with variable length, were used. The physical−chemical properties, thermal behavior, mechanical, electrical, and bending responses of the PVDF/IL composites were evaluated. The incorporation of ILs into the PVDF matrix leads to an increase of the electroactive β phase content. Moreover, the β phase content increases with the increase of the IL alkyl chain length. The degree of crystallinity depends on the IL chain length as well as on the mechanical properties, revealing the plasticizing behavior exerted by the IL. The electrical conductivity decreased with the increase of the cation alkyl chain size. The highest bending response was observed for the [Pmim][TFSI]/PVDF and [Pmpip][TFSI] composites (where Pmim and Pmpip represent propylimidazolium and propylmethylpiperidinium), being 5.7 and 6.0 mm, respectively, at 5 V and 100 mHz.

Cellulose Nanocrystal and Water-Soluble Cellulose Derivative Based Electromechanical Bending Actuators

“…Besides inducing the PVDF crystallization into the highly polar and electroactive β-phase, the incorporation of IL enhances the electrical conductivity and also decreases the Young´s modulus of the polymer. Similar results were obtained by the incorporation of different ILs with a common anion [TFSI]and distinct cations [12], as well as by the introduction of IL in different polymer matrices such as poly(L-lactic acid) (PLLA) [13], poly(ε-caprolactone) (PCL) [14], and poly(ethylene oxide) (PEO) [15].…”

Development of Poly(l-Lactic Acid)-Based Bending Actuators

“…The nominal E value was deduced from the linear regime of the elastic region and using the tangent method ( Figure 6 and Table S2). Figure 6 and [20,25]. For the PLLA samples dried at room temperature, no relevant changes are observed in E value when the post-thermal treatment temperature was increased from 70 • C (1840 ± 330 MPa) to 140 • C (2000 ± 100 MPa).…”

“…The [Emim][TFSI] was selected, attending to its good miscibility with the DMC and its electrical conductivity (6.63 mS/cm, data obtained from the provider). Moreover, a concentration of 40 wt% was used attending to the commonly maximum IL concentration used in IL/polymer blends for actuator applications, as reported in our previous studies [25]. Then, PLLA was added and after its complete dissolution, the resulting solution was spread onto a glass substrate and left to dry, either at room temperature or at 50 • C in an oven.…”

“…where R is the electrical resistance, L is the sample thickness and A is the area of the electrodes. The performance of the films as actuators was evaluated by bending tests in a home-made samples holder [25]. Prior to the measurements, the samples with dimensions of 12 mm × 2 mm were covered with Au on both sides by magnetron sputtering (Polaron SC502).…”

Physico‐Chemical Characterizations of Poly(vinylidene fluoride)/Cu3(BTC)2 Composite Membranes Prepared by In Situ Crystal Growth

“…The choice of PVDF was encouraged by its ability to form homogenous solution with metallic salts. In addition, thanks to the outstanding electroactive properties of its β ‐phase, PVDF and its membranes are important materials with extensively technological applications such as membrane distillation sensors , lithium‐ion battery , energy harvesting , and actuators .…”