Humidity Sensors Based on Magnetic Ionic Liquids Blended in Poly(vinylidene fluoride-co-hexafluoropropylene)

Abstract

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) films incorporating 40 wt % of different types of imidazolium ionic liquids (ILs) comprising different magnetic anions (tetrachloroferrate [FeCl 4 ] − , tetrathiocyanatocobaltate [Co(SCN) 4 ] 2− , and tetrachlorocobaltate [CoCl 4 ] 2− ) and imidazolium cation chain lengths (1-butyl-3-methylimidazolium and 1ethyl-3-methylimidazolium) have been developed for humiditysensing applications. The influence of the different ILs on the morphology of the IL/PVDF-HFP composites has been evaluated, with a porous structure observed independently of the IL anion type and cation chain length. The inclusion of the ILs into PVDF-HFP induces polymer crystallization into the electroactive β phase, with the increase more noticeable for PVDF-HFP/[Bmim][FeCl 4 ], which reaches a β phase content of 85%. The degree of crystallinity slightly decreases with the incorporation of the filler and the incorporation of [Bmim] 2 [CoCl 4 ], [Bmim] 2 [Co(SCN) 4 ], and [Emim] 2 [Co(SCN) 4 ], leading to a degree of crystallinity between 11 and 13%. A decrease in the thermal stability and yield strength is observed in the hybrid samples with respect to neat PVDF-HFP, with this decrease being more noticeable for the PVDF-HFP/[Bmim] 2 [Co(SCN) 4 ] samples. Further, the highest magnetization has been obtained for the PVDF-HFP/[Bmim] 2 [Co-(SCN) 4 ] and PVDF-HFP/[Bmim][FeCl 4 ] composites with similar filler concentrations. The suitability of the developed materials for humidity sensing has been evaluated by analyzing the impedance variation with varying relative humidity from 30 to 85%. [Bmim] 2 [CoCl 4 ]/PVDF-HFP displays the highest relative humidity (RH) sensing response of −2245 ± 240 Ω/RH. Finally, the applicability of the developed hybrid IL/polymer composites has been demonstrated by the development of a real-time breathing monitoring device.

Synergistic Interface Platforms: Designing Superhydrophilic Conductive Nanoparticle‐Decorated Nanofibrous Membranes

“…This interpretation agrees with previously published works. [35][36][37] The presence of PPy is confirmed by the observed absorption bands at 1992, 1530, and 1620 cm −1 (corresponding to C = C and C-C stretching modes of the pyrrole ring), the secondary heterocyclic amine at ≈1275 cm −1 (attributed to the C-N stretching mode of the pyrrole ring), and the breathing C-H bipolaron vibration bands of the pyrrole rings at 1160 and 1022 cm −1 . Peaks below 1000 cm −1 indicate skeletal vibrations of the polymer.…”

Wrinkled Structure and Morphology Transition of Poly(vinylidene Fluoride Cohexafluoropropylene) Films for Smart Windows

“…30 The inclusion of hexafluoropropylene (HFP) into PVDF to form the poly-(vinylidene fluoride cohexafluoropropylene) PVDF-HFP structure can improve the hydrophobicity of membrane and lower the crystallinity property. 31 It has been shown that ionic liquids can be used as property control agents for PVDF-HFP membrane, which can affect the morphology, 32 water absorption capacity, 33 and mechanical properties of the membrane. 34 As PVDF-HFP membranes are hydrophobic, the addition of hydrophilic ionic liquids can modulate their hydrophobicity and, thus, impart water responsiveness.…”