Flexoelectricity of Multifunctional Polymer Electrolyte Membranes: Effect of Polymer Network Functionality

Abstract

The phenomenon of flexoelectricity generation in flexible, thermally cross-linked, ionic multifunctional polymer electrolyte membranes (PEMs) was investigated subjected to mechanical deformation by bending. The effect of copolymer ratios of functional branched poly(ethylene imine) (PEI) and poly(ethylene glycol) diglycidyl ether (PEGDGE) on the mechanoelectrical transduction in their PEMs was demonstrated at a fixed lithium bis(trifluoromethane sulfonyl) imide (LiTFSI) content. By changing the PEI and PEGDGE copolymer ratios, the constructed co-networks comprised of various amines (primary, secondary, and tertiary) to ethylene oxide ratios, revealed distinctively different flexoelectric responses. With increasing the amount of PEGDGE, the multifunctional PEM exhibited not only lower glass transition temperature but also higher ionic conductivities. This finding may be attributed to the higher content of the linear ethylene oxide chain, which promotes both higher segmental motion and lithium ion complexation with ether oxygen. The examination of the flexoelectric response of the various multifunctional PEMs as a function of composition was performed under intermittent square-waves and sinusoidal bending modes along with flexoelectric responses as a function of relaxation time or frequency. A remarkable flexoelectric coefficient (μ = 210.1 μC/ m) was obtained without requiring plasticization or network modification. The energy conversion efficiency of various PEMs was determined in order to evaluate potential applications in energy harvesting devices and sensors. The developed process of PEM fabrication involving thermal curing is compatible and scalable to current commercial processes such as tire vulcanization and shape conformable 3D printing for soft sensors and energy harvesters.

Tuning the Mechanoelectrical Transduction Performance of Multifunctional Polymer Electrolyte Membranes via Variation of Precursor Molecular Weight

“…The ionic polarization of a flexoionic laminate was shown to decrease upon increasing the bending frequency, leading to partial ion polarization. All flexoelectric coefficients calculated at the oscillatory bending were 2 orders of magnitude lower than the flexoelectric coefficients obtained in the intermittent mode, irrespective of the copolymer composition, which is in agreement with our previously reported works. , …”

“…Short circuit current exhibited a different behavior in response to intermittent bending, where a sharp increase in the current was observed when the laminate was bent, forming a spike-like signal similar to the previously reported response. 33 This was followed by an exponential decaying current back to the static constant current (I o ) for the rest of the rectangular bending. An identical pulse in the shape and amplitude but in the negative current direction was recorded upon releasing the laminate.…”

“…The proposed strategy of increasing the molecular weight of the ion-solvating polymer as a means of enhancing energy conversion efficiency was found to be successful, i.e., reaching 13.7% for the PEI-co-PEGDGE1000/ LiTFSI (95/5) laminate, which is 6-and 34-fold enhancement relative to those of the PEMs based on PEGDGE500 and PEGDGE200, respectively. 32 1.4 μC/m auditory hair 29 ∼0.1 nC/m human bone 9 ∼2.3 nC/m PVDF 26,27 5−13 nC/m polythiophene-based compound 28 ∼7 μC/m bent-core nematic liquid crystal 18 60 nC/m ionic liquid crystal elastomer (i-LCE) 31 25−220 μC/m PEM(PEGDA/SCN/LiTFSI) 30 29−323 μC/m 1−2 PEM(TS-PEGDA/IL) 48 84−154 μC/m ∼1 PEGDA/(K-, Na-, Mg-, Al-(TFSI) 3 ) 50 18−45 μC/m 0.4−2.6 PEGDA-co-PEGMEA/LiTFSI 95/5 33 64−230 μC/m 0.9−6.…”

Electrochemical Performance of Highly Ion-Conductive Polymer Electrolyte Membranes Based on Polyoxide-tetrathiol Conetwork for Lithium Metal Batteries

“…The elongation at break of the dry film was found to be ∼16% strain, which is lower than their corresponding plasticized PEMs breaking at ∼27% strain. This PEM revealed superior tensile properties compared to similar reported PEMs based on difunctional PEGDA and cross-linked thiosiloxane–PEGDA ,, but comparable performance to PEMs based on PEGDGE and PEI. , Upon increasing the amount of PETMP, that I,s (60:40)/40/40 (TMPETA- co -PETMP/SCN/LiTFSI), the plasticized PEMs exhibited lower mechanical strength, modulus, and elongation at break. The mechanical strength and elongation at break of the (60:40)/40/40 PEM decreased by 3-folds and about 2-folds, respectively, as compared to the (70:30)/40/40 PEM.…”

Large Curvature Sensors Based on Flexoelectric Effect in PEDOT:PSS Polymer Films

“…This difference lies mainly in the flexoelectric polymer used and the flexibility of the device. Only work on flexible solid-state polymer electrolyte membranes (PEMs) based on poly(ethylene glycol) diacrylate (PEGDA) polymer and poly(ethylene imine) (PEI)-poly-(ethylene glycol) diglycidyl ether (PEGDGE) copolymer combined with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) 57,59 present coefficients higher than those of this work. However, they are much more difficult to make with the integration of different polymers or doping with hydrophilic salts.…”