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Review

A Succinct Review on the PVDF/Imidazolium-Based Ionic Liquid Blends and Composites: Preparations, Properties, and Applications

by
Ahmad Adlie Shamsuri
1,*,
Rusli Daik
2,* and
Siti Nurul Ain Md. Jamil
3,4
1
Laboratory of Biocomposite Technology, Institute of Tropical Forestry and Forest Products, Universiti Putra Malaysia, UPM Serdang 43400, Selangor, Malaysia
2
Department of Chemical Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi 43600, Selangor, Malaysia
3
Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, UPM Serdang 43400, Selangor, Malaysia
4
Centre of Foundation Studies for Agricultural Science, Universiti Putra Malaysia, UPM Serdang 43400, Selangor, Malaysia
*
Authors to whom correspondence should be addressed.
Processes 2021, 9(5), 761; https://doi.org/10.3390/pr9050761
Submission received: 4 April 2021 / Revised: 22 April 2021 / Accepted: 24 April 2021 / Published: 27 April 2021
(This article belongs to the Special Issue Tailoring Polymeric Materials for Specific Applications)
Browse Figures
Versions Notes

Abstract

:
Poly(vinylidene fluoride) (PVDF) is a versatile thermoplastic fluoropolymer with intriguing characteristics, which is receiving considerable attention from researchers in many areas. Recently, PVDF and its copolymer, such as poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) have been blended with ionic liquids to produce blend and composite materials for target applications. In this succinct review, two types of ionic liquids that are utilized for the preparation of PVDF and PVDF-HFP blends and composites, namely, hydrophilic and hydrophobic imidazolium-based ionic liquids, are reviewed. In addition, the effect of the ionic liquids on the physicochemical properties of the PVDF and PVDF-HFP blends and composites, is described as well. On top of that, a multitude of applications of the blends and composites are also succinctly reviewed. This review may give inspirations to the polymer blend and composite researchers in diversifying the applications of thermoplastic fluoropolymers through the utilization of ionic liquids.

1. Introduction

These days, polymers can be tailor-made for specific applications, it can be done by chemically modifying the polymer functional groups and side chains [1]. On the other hand, some polymers can physically be modified by utilizing ionic compounds, such as ionic liquids for target applications. Lately, thermoplastic fluoropolymer, for example, poly(vinylidene fluoride) (PVDF) is blended with ionic liquids to produce blend and composite materials for a multitude of applications. PVDF is made from vinylidene fluoride monomer through a free-radical polymerization process. Figure 1 shows the schematic of the polymerization of vinylidene fluoride to make PVDF. In addition, PVDF copolymer, such as poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) is also blended with ionic liquids to produce blends and composites for a wide variety of applications. PVDF-HFP is made via copolymerization process by means of two different monomers [2]. Figure 2 indicates the schematic of the copolymerization of vinylidene fluoride with hexafluoropropylene to make PVDF-HFP. The significant advantages of PVDF and PVDF-HFP are their solubility in organic solvents and their capability to use in electronic and electric applications.
Ionic liquids are ionic compounds that have liquid property below 100 °C. They are non-volatile since they have a low vapor pressure. Ionic liquids are also regarded as an environmentally benign solvent because they can be recycled [3]. Moreover, ionic liquids have interesting solvent properties, for instance, good solubility with countless organic solvents, high thermal stability, good electrical conductivity, high polarity, and non-flammability [4]. They also possess the aptitude to dissolve most organic materials, including biopolymers and some inorganic materials. In addition, ionic liquids can be created according to the necessities of the usage [5]. The utilization of ionic liquids on the PVDF and PVDF-HFP is a practical approach for the preparation of blends and composites with multiple functions. In numerous types of ionic liquids, imidazolium-based ionic liquids are frequently utilized for that purpose. This is because of the efficiency and unique properties of the ionic liquids [6]. Nonetheless, many imidazolium-based ionic liquids have similar cations but distinct counter anions that commonly possess different hydrophobicity. Therefore, in this succinct review, they have been classified into two types, specifically hydrophilic and hydrophobic imidazolium-based ionic liquids.
Table 1 demonstrates examples of hydrophilic imidazolium-based ionic liquids utilized for preparation of PVDF and PVDF-HFP blends and composites. It can be observed that the hydrophilic ionic liquids with halide counter anions (Cl¯, Br¯, and I¯) have repeatedly been utilized, followed by tetrafluoroborate counter anion (BF4¯). This is probably because of their easier availability and cost-effectiveness compared to other hydrophilic ionic liquids. On the other hand, OAc¯, DCA¯, H2PO4¯, EtSO4¯, NO3¯, SCN¯, and CF3SO3¯ counter anions are rarely utilized, but they can play a potential role in the blends and composites. Figure 3 exhibits the chemical structures of hydrophilic imidazolium-based ionic liquids collected in Table 1. Meanwhile, Table 2 exhibits examples of hydrophobic imidazolium-based ionic liquids utilized for preparation of PVDF and PVDF-HFP blends and composites. It is seen that the counter anions, such as NTf2¯, TFSA¯, FSI¯, FAP¯, PF6¯, and B(CN)4¯ contribute to the hydrophobic property of the ionic liquids regardless of the type of the imidazolium cations. However, BF4¯ counter anion can exhibit both hydrophilic and hydrophobic properties. This phenomenon is influenced by the length of the cation alkyl chain [6]. That is why [Hmim][BF4] is hydrophobic, whereas [Emim][BF4], [Bmim][BF4], and [Veim][BF4] are hydrophilic. Figure 4 demonstrates the chemical structures of hydrophobic imidazolium-based ionic liquids collected in Table 2.
Table 3 displays examples of fillers modified with imidazolium-based ionic liquids for preparation of PVDF and PVDF-HFP composites. It can be perceived that the allotropes of carbon, such as graphene, graphene oxide, and carbon nanotubes can be modified with the ionic liquids [17,32,39]. Clay mineral like montmorillonite can not only be modified with surfactants [62,63] but also with the ionic liquids [10,15]. Additionally, metal oxides, for example, titanium dioxide and silicon dioxide have been modified with the ionic liquids [36,52]. On top of that, organic materials, for instance, polyvinyl pyrrolidone grains and succinonitrile have also been modified with the ionic liquids [31,37]. The utilization of the ionic liquids as modifiers can provide an advantage because of their exceptional chemical structures that are able to interact with PVDF and PVDF-HFP, as well as inorganic and organic fillers. This consequently improves the interfacial bonding between the polymer matrix and filler. In addition, to the best knowledge of the authors, no succinct review has been conceived encompassing the study on the preparations, properties, and applications of PVDF/and PVDF-HFP/imidazolium-based ionic liquid blends and composites. That is the rationale of conceiving an organized review in this paper.

2. Preparations of PVDF and PVDF-HFP Blends and Composites

2.1. PVDF/and PVDF-HFP/Hydrophilic Imidazolium-Based Ionic Liquid Blends

Table 4 shows the types of polymer matrices, hydrophilic imidazolium-based ionic liquids, and preparation processes of PVDF and PVDF-HFP blends. It can be observed that the PVDF is more often used as a polymer matrix in comparison to PVDF-HFP. This is possibly due to PVDF-HFP lack of attention in the preparation of polymer/ionic liquid blends. On top of that, the blending process between the ionic liquids and PVDF can be conducted via solution blending in polar aprotic solvents, such as dimethylformamide [8,9], dimethylacetamide [23], and 1-methyl-2-pyrrolidone [27]. In addition, PVDF can also be blended with the ionic liquids through solventless ways, namely liquid impregnation and melt blending. Liquid impregnation can be done by impregnating PVDF in an ionic liquid at room temperature for 48 h [21], whilst melt blending can be carried out at 190 °C for 0.12 h [12,13]. Thus, the fastest way to blend between the ionic liquids and PVDF is through melt blending, but it requires a specific blending machine and a hot-pressing machine to shape the blends. Meanwhile, as for PVDF-HFP, it can be blended with the ionic liquids via soaking in an ionic liquid at room temperature for 24 h [19], and solution blending in low boiling point polar aprotic solvent like acetone [34,35].

2.2. PVDF/and PVDF-HFP/Hydrophobic Imidazolium-Based Ionic Liquid Blends

Table 5 indicates the types of polymer matrices, hydrophobic imidazolium-based ionic liquids, and preparation processes of PVDF and PVDF-HFP blends. It is seen that the PVDF is also preferred for the preparation of polymer/ionic liquid blends than the PVDF-HFP. In addition, the solution blending is mainly done as well in preparation of the blends. However, liquid impregnation can be performed in a hydrophobic ionic liquid at room temperature for 0.5 h only [49], which has less impregnation time compared to the hydrophilic ionic liquid. On the other hand, the solution blending is typically conducted at room temperature regardless of the type of the imidazolium-based ionic liquids. However, elevated temperatures are also used for shortening the blending process. Lastly, the final process is essentially important for molding the blends prior to physicochemical characterization and actual application. The final process for the solution blending can be carried out through solution casting by pouring the solution on leveled glass plates and evaporating solvent at high or room temperature for certain or 24 h. The process has normally been applied for the production of the free-standing film [64]. Nevertheless, hot pressing can also be done to obtain the desired shape of the blends [59]. Additionally, the spin-coating can be operated as well after the solution blending [51].

2.3. PVDF/and PVDF-HFP/Ionic Liquid-Modified Filler Composites

Table 6 exhibits the types of polymer matrices, fillers, imidazolium-based ionic liquids, and preparation processes of PVDF and PVDF-HFP composites. Most of the fillers have been modified with the ionic liquids before the mixing process with the polymer matrices. In addition, the modification of the fillers with the imidazolium-based ionic liquids can be carried out through ultrasonication [20], stirring [7,10,14,17,18], and grinding [38,39,48,56,57,58] processes. The mixing process between the polymer matrices and modified fillers can be conducted via melt blending, solution blending, ultrasonication, and sonication. PVDF and the modified fillers can be processed via melt blending at a temperature range from 190 to 220 °C for less than 0.34 h. On top of that, solution blending between the polymer matrices and modified fillers can be done in polar aprotic solvents at room or elevated temperatures. Meanwhile, for ultrasonication [14,15,17] and sonication [18,36,52], they are usually performed in the solvents at room temperature, but require less time compared to the solution blending. The final processes, such as hot pressing, solution casting, compression molding, and soaking have also been employed to obtain characterizable and appliable PVDF and PVDF-HFP composites.

3. Effect of Imidazolium-Based Ionic Liquids on the Physicochemical Properties of the Blends and Composites

3.1. Effect of Hydrophilic Imidazolium-Based Ionic Liquids

Table 7 shows the physicochemical properties of PVDF/and PVDF-HFP/hydrophilic imidazolium-based ionic liquid blends and composites. PVDF was blended with [Emim][Cl] ionic liquid for the preparation of a PVDF/[Emim][Cl] blend [9]. The crystalline, mechanical, thermal, and chemical properties of the blend were characterized by means of differential scanning calorimeter, universal testing machine, and FTIR spectrometer. The crystalline properties, such as the crystallinity degree of the blend decreased, which was attributed to the existence of interactions between the ionic liquid and PVDF matrix. Moreover, the mechanical properties, such as the elastic modulus of the blend decreased because of the presence of [Emim][Cl], which acted as a plasticizer. In addition, the thermal properties, such as the melting temperature of the blend decreased owing to the strong electrostatic interactions between the polymer chains and the ionic liquid, which possessed a high nucleation effect. On the other hand, the chemical properties, such as the characteristic absorption bands of the α-phase, of the blend are completely disappeared, and β-phase absorption bands appeared very intensively compared to the neat PVDF. This was due to the existence of strong local dipole moments within the blend [9]. Therefore, it can be concluded that PVDF blended with [Emim][Cl] ionic liquid provides low crystallinity degree and elastic modulus blend, as well as low melting temperature, but its components have good interactions.
Meanwhile, PVDF-HFP was blended with different amounts of [Bmim][BF4] ionic liquid for the preparation of PVDF-HFP/[Bmim][BF4] blends [35]. The crystalline, thermal, and chemical properties of the blends were characterized by using X-ray diffractometer, differential scanning calorimeter, and FTIR spectrometer. The crystalline properties, such as the degree of crystallinity of the blends decreased, which was caused by the inclusion of ionic liquid in the polymer matrix. Additionally, the thermal properties, such as the melting temperature of the blends decreased because of the plasticization effect of [Bmim][BF4], as well as due to its complexation with the PVDF-HFP backbone. On top of that, the chemical properties, such as the absorption bands of the C−H stretching vibrations, of the blends shifted to lower wavenumber regions in comparison to the C−H stretching vibrations of the neat PVDF-HFP. This was attributed to the substantial conformational changes that occurred in the PVDF-HFP matrix after complexation with ionic liquid [35]. Thus, it can be inferred that PVDF-HFP blended with [Bmim][BF4] ionic liquid gives low crystallinity degree and melting temperature blends. However, their components have a good interaction.
In addition, MWCNT-COOH modified with [Aeim][Br] ionic liquid was used for the preparation of PVDF/MWCNT-COOH-[Aeim][Br] composites [18]. The crystalline, mechanical, thermal, and chemical properties of the composites were characterized by means of X-ray diffractometer, universal testing machine, differential scanning calorimeter, and FTIR spectrometer. The crystalline properties, such as the crystallization peaks of the composite (1.0 wt.%) decreased because of the formation and stabilization of β-phase in the composite. Nevertheless, the mechanical properties, such as the Young’s modulus, tensile strength, elongation at break, and toughness, of the composite (0.5 wt.%) significantly increased by up to 55%, 328%, 39%, and 160%, respectively, compared to the neat PVDF. This was caused by the reinforcing and toughening effects of [Aeim][Br]-modified MWCNT-COOH on the composite. Furthermore, the thermal properties, such as the melting temperature of the composite (1.0 wt.%), increased by up to 6.1% in comparison to the neat PVDF. This was because of the homogeneous dispersion of modified MWCNT-COOH, which caused a compact and higher melting crystal. On the other hand, the chemical properties, such as the absorption bands of the CF−CH−CF bending vibrations, of the composites shifted to higher wavenumber regions compared to the CF−CH−CF bending vibration of the neat PVDF. This was due to the dipole-dipole interaction between the >CF2 dipoles of PVDF and imidazolium cations of modified MWCNT-COOH [18]. Hence, it can be deduced that PVDF mixed with MWCNT-COOH-[Aeim][Br] grants high tensile strength and toughness composites, as well as high melting temperature with good interaction of their components.
PVDF, PVP grains, and [Emim][BF4] ionic liquid were used for the preparation of a PVDF/PVP/[Emim][BF4] composite [31]. The crystalline, mechanical, thermal, and chemical properties of the composite were characterized by using X-ray diffractometer, nanoindentation, differential scanning calorimeter, and FTIR spectrometer. The crystalline properties, such as the α-phase peaks intensity of the composite decreased, which was attributed to the introduction of PVP and ionic liquid into the PVDF matrix, which also increased the β-phase. Moreover, the mechanical properties, such as the Young’s modulus and tensile strength of the composite decreased because of the plasticizing effect of [Emim][BF4]. In addition, the thermal properties, such as the melting temperature of the composite decreased owing to the existence of interactions among PVDF, PVP, and ionic liquid. On top of that, the chemical properties, such as the characteristic absorption bands of PVDF, PVP, and [Emim][BF4] are present in the composite. This was due to the strong electrostatic interactions of PVP and ionic liquid with the active hydrogen group on PVDF [31]. Therefore, it can be concluded that PVDF mixed with PVP grains and [Emim][BF4] ionic liquid provides low Young’s modulus and tensile strength composite, as well as low melting temperature, but its components have good interactions.
Meanwhile, PVDF-HFP, OMMT, and [Bmim][Br] ionic liquid were used for the preparation of PVDF-HFP/OMMT/[Bmim][Br] composites [15]. The crystalline, thermal, and chemical properties of the composites were characterized by means of X-ray diffractometer, thermogravimetric analyzer, and FTIR spectrometer. The crystalline properties, such as the crystallinity pattern of the composites decreased, which was caused by the formation of highly amorphous composites. Additionally, the thermal properties, such as the decomposition temperature of the composites decreased because of the complexation of [Bmim]+ cations of ionic liquid with the PVDF-HFP, which destabilized the C−H bonds of the polymer matrix. On the other hand, the chemical properties, such as the absorption bands of the Si−O bond, of the composites shifted to lower wavenumber regions, and their intensity decreased sharply in comparison to the Si−O bond of the OMMT. This was attributed to the successful intercalation of PVDF-HFP into the galleries of the OMMT [15]. Thus, it can be inferred that PVDF-HFP mixed with OMMT and [Bmim][Br] ionic liquid gives low crystallinity and decomposition temperature composites. However, their components have a good interaction.
In addition, PVDF-HFP, SN, and [Emim][CF3SO3] ionic liquid were used for the preparation of PVDF-HFP/SN/[Emim][CF3SO3] composites [40]. The crystalline, thermal, and chemical properties of the composites were characterized by using X-ray diffractometer, differential scanning calorimeter, and FTIR spectrometer. The crystalline properties, such as the crystallization peaks of the composites decreased because of the predominant amorphous nature of the composites. Nevertheless, the thermal properties, such as the melting temperature of the composite (10 wt.%) significantly increased by up to 21% compared to the pure PVDF-HFP. This was caused by the phase transition of the composite that occurred from the ordered phase to the disordered phase. On top of that, the chemical properties, such as the absorption band of the amorphous phase, of the composite became considerably narrower in comparison to the amorphous phase of the pure PVDF-HFP. This was due to the interaction between the nitrile group of SN and the PVDF-HFP backbone [40]. Hence, it can be deduced that PVDF-HFP mixed with SN and [Emim][CF3SO3] ionic liquid grants low crystallinity and high melting temperature composites with good interaction of their components.

3.2. Effect of Hydrophobic Imidazolium-Based Ionic Liquids

Table 8 displays the physicochemical properties of PVDF/and PVDF-HFP/hydrophobic imidazolium-based ionic liquid blends and composites. PVDF was blended with different contents of [Emim][NTf2] ionic liquid for the preparation of PVDF/[Emim][NTf2] blends [43]. The crystalline, mechanical, thermal, and chemical properties of the blends were characterized by means of differential scanning calorimeter, autograph universal testing machine, and FTIR spectrometer. The crystalline properties, such as the degree of crystallinity of the blends decreased, which was attributed to the existence of interactions of the ionic liquid with the polymer matrix. Furthermore, the mechanical properties, such as the elastic modulus and yielding stress of the blends decreased because of the presence of [Emim][NTf2], which acted as a plasticizer for PVDF. Additionally, the thermal properties, such as the melting temperature of the blends decreased owing to the destabilization of the crystalline phase. On the other hand, the chemical properties, such as the characteristic absorption bands of the polar β-phase are present in all the blends compared to the neat PVDF, and their intensity increased for the larger ionic liquid contents. This was due to the strong electrostatic interactions of the ionic liquid with the dipoles of the polymer chains, which gave rise to the nucleation of the β-phase of the polymer [43]. Therefore, it can be concluded that PVDF blended with [Emim][NTf2] ionic liquid provides low elastic modulus and yielding stress blends, as well as low melting temperature, but their components have good interactions.
Meanwhile, PVDF was blended with different amounts of [Bmim][PF6] ionic liquid for the preparation of PVDF/[Bmim][PF6] blends [55]. The crystalline, mechanical, thermal, and chemical properties of the blends were characterized by using X-ray diffractometer, universal testing machine, differential scanning calorimeter, and FTIR spectrometer. The crystalline properties, such as the α characteristic peaks of the blends disappeared, which was due to the decrease of α-phase content in the blends. Nonetheless, the mechanical properties, such as the tensile strength and elongation at break of the blend (100/20) significantly increased by up to 77% and 173%, respectively, compared to the neat PVDF. This was caused by the improvement of the ductility of the blend, which enhanced stretchability and strength at break simultaneously. Moreover, the thermal properties, such as the melting temperature of the blend (100/2), considerably increased by up to 5.3% in comparison to the neat PVDF. This was because of the transformation of the nonpolar α-phase for PVDF to the polar γ-phase with the introduction of a small amount of ionic liquid. On top of that, the chemical properties, such as the absorption bands of the CF2−CH2 bending vibrations, of the blends shifted to higher wavenumber regions compared to the CF2−CH2 bending vibration of the neat PVDF. This was due to the >CF2 groups in the PVDF chains have specific interactions with the imidazolium ring in the ionic liquid [55]. Thus, it can be inferred that PVDF blended with [Bmim][PF6] ionic liquid gives high tensile strength and elongation blends, as well as high melting temperature with good interactions of their components.
In addition, PVDF-HFP was blended with different contents of [Emim][NTf2] ionic liquid for the preparation of PVDF-HFP/[Emim][NTf2] blends [47]. The crystalline, mechanical, thermal, and chemical properties of the blends were characterized by means of universal testing machine, differential scanning calorimeter, and FTIR spectrometer. The crystalline properties, such as the degree of crystallinity of the blends decreased, which was attributed to the strong interaction of the ionic liquid with the polar units. Moreover, the mechanical properties, such as the tensile stress and Young’s modulus of the blends decreased because of the introduction of [Emim][NTf2] into the polymer matrix, which induced a plasticizing behavior of the blends. In addition, the thermal properties, such as the melting temperature of the blends decreased owing to the plasticization effect of the ionic liquid and its complexation with the PVDF-HFP backbone. On the other hand, the chemical properties, such as the characteristic absorption bands of the β-phase content of the blends increased, which was due to the nucleation of the β-phase through the electrostatic interactions between the imidazolium cations of the ionic liquid and the negatively polarized CF2 groups of PVDF-HFP [47]. Hence, it can be deduced that PVDF-HFP blended with [Emim][NTf2] ionic liquid grants low tensile stress and Young’s modulus blends, as well as low melting temperature. However, their components have good interactions.
MWCNTs modified with [Emim][NTf2] ionic liquid was used for the preparation of PVDF/MWCNTs-[Emim][NTf2] composites [48]. The crystalline, mechanical, thermal, and chemical properties of the composites were characterized by using X-ray diffractometer, micro universal testing machine, differential scanning calorimeter, and FTIR spectrometer. The crystalline properties, such as the α-phase peaks intensity of the composites decreased, which was attributed to the presence of the [Emim][NTf2]-modified MWCNTs in the composites, which also induced the formation of the γ-phase from α-phase. Nonetheless, the mechanical properties, such as the tensile strength, elongation at break, and Young’s modulus of the composite (1.0 wt.%) increased by up to 14%, 20%, and 3.1%, respectively, compared to the neat PVDF. This was because of the improvement of the strength and ductility of the composite. In addition, the thermal properties, such as the melting temperature of the composite (1.0 wt.%) increased by up to 4.5% in comparison to the neat PVDF. This was owing to the existence of polar γ-phase in the composite, whereby its melting temperature was higher than the nonpolar α-phase. On top of that, the chemical properties, such as the absorption bands of the CH−CF−CH stretching vibrations, of the composites shifted to higher wavenumber regions compared to the CH−CF−CH stretching vibration of the neat PVDF. This was due to the electrostatic interaction between the anion of the ionic liquid and PVDF [48]. Therefore, it can be concluded that PVDF mixed with MWCNTs-[Emim][NTf2] provides high tensile strength and elongation composites, as well as high melting temperature with good interaction of their components.
Meanwhile, MWCNTs modified with [Bmim][PF6] ionic liquid was used for the preparation of PVDF/MWCNTs-[Bmim][PF6] composites [57]. The crystalline, thermal, and chemical properties of the composites were characterized by means of X-ray diffractometer, differential scanning calorimeter, and FTIR spectrometer. The crystalline properties, such as the α characteristic diffraction peaks intensity of the composites decreased, which was caused by the increase of polar phases amount formed in the composites. Additionally, the thermal properties, such as the melting temperature of the composite (1:1) significantly increased by up to 4.8% in comparison to the neat PVDF. This was because the polar phases in the composite possess a higher melting temperature than the nonpolar phase in the polymer. On the other hand, the chemical properties, such as the absorption bands of the CF2−CH2 bending vibrations, of the composites shifted to higher wavenumber regions compared to the CF2−CH2 bending vibration of the neat PVDF. This was attributed to the specific interactions of the >CF2 groups in the polymer chains with the imidazolium ring in the ionic liquid-modified MWCNTs [57]. Thus, it can be inferred that PVDF mixed with MWCNTs-[Bmim][PF6] gives low crystallinity and high melting temperature composites with good interactions of their components.
In addition, MWCNT-COOH modified with [Bmim][PF6] ionic liquid was used for the preparation of PVDF/MWCNT-COOH-[Bmim][PF6] composites [56]. The crystalline, mechanical, and chemical properties of the composites were characterized by using tensile machine and FTIR spectrometer. The crystalline properties, such as the absorption peaks of the nonpolar α-phase crystals of the composites disappeared, which was attributed to the formation of polar β- and γ-phase crystals in the composites, which also resulted from the interfacial interactions between the PVDF chains and [Bmim][PF6]-modified MWCNT-COOH. Nevertheless, the mechanical properties, such as the elongation at break of the composite (10:2) significantly increased by up to 326% compared to the neat PVDF. This was because of the presence of modified MWCNT-COOH, which induced toughness improvement of the composite. On top of that, the chemical properties, such as the absorption bands of the −CF2 stretching vibrations, of the composites shifted to lower wavenumber regions in comparison to the −CF2 stretching vibration of the neat PVDF. This was due to the interactions between the −CF2 and imidazolium rings on ionic liquid-modified MWCNT-COOH [56]. Hence, it can be deduced that PVDF mixed with MWCNT-COOH-[Bmim][PF6] grants low nonpolar crystals and high elongation at break composites with good interactions of their components.

4. Applications of PVDF and PVDF-HFP Blends and Composites

4.1. PVDF/and PVDF-HFP/Hydrophilic Imidazolium-Based Ionic Liquid Blends and Composites

Table 9 shows the applications of PVDF/and PVDF-HFP/hydrophilic imidazolium-based ionic liquid blends and composites. It can be observed that the hydrophilic ionic liquids are frequently utilized in PVDF and PVDF-HFP blends and composites, this is probably due to their low cost and ready availability. On the other hand, the blends and composites are predominantly employed in electronic and electric applications, for instance, capacitors [20,22,26], electrolyte membranes [34,35], dielectric composites [38,39], and actuators [9,11]. Furthermore, they are also applied in gas processing, for example, carbon dioxide capture [21], as well as in water and wastewater treatment as antifouling membranes [7]. The utilization of [Emim][DCA] exhibits double advantages in PVDF-HFP blends, specifically it provided additional charge carriers, and it also reduced the crystallinity of polymer matrix, which consequently increased the ionic conductivity of the fabricated capacitors [22]. Moreover, the value of ionic conductivity of PVDF-HFP blends increases with an increase in the interaction of [Bmim][I] with the polymer matrix, which facilitated the ionic motion of electrolyte membranes [19]. Additionally, [Veim][BF4] was utilized in PVDF/MWCNTs composites increased the dispersion of filler in the polymer matrix and induced the polar β-phase of the composites, which improved their dielectric constant by up to three times than the neat PVDF [38]. Furthermore, the bending movement of the PVDF blends increases with increasing [Hmim][Cl] content, which ascribed to their low degree of crystallinity and elastic modulus, and high AC electrical conductivity value of the prepared actuators [11].

4.2. PVDF/and PVDF-HFP/Hydrophobic Imidazolium-Based Ionic Liquid Blends and Composites

Table 10 indicates the applications of PVDF/and PVDF-HFP/hydrophobic imidazolium-based ionic liquid blends and composites. It is seen that the blends and composites are typically utilized for application in electronic and electric, for example, capacitors [46,52], actuators [8,9], polymer electrolytes [50,59], sensor [27], anti-electrostatic films [55], flexible organic memory [51], flexible dielectric [58], and electromagnetic interference shield [48]. In addition, they can also be applied in gas processing as membranes for the separation of carbon dioxide [49,60]. The utilization of PVDF-HFP/[Emim][NTf2] blend in the fabricated capacitor increased the specific capacitance at high current density, which exhibited superior performances [46]. Meanwhile, the bending response of prepared actuators also depends on the content of [Emim][NTf2] in PVDF, which increased with increasing ionic liquid content and the blend thickness [8]. On the other hand, the polymer electrolyte prepared from the PVDF/[Bzmim][PF6] blends possesses high values of the DC conductivity, which was induced by the increase of polar phase, ion mobility, and ion concentration [59]. The gas sensor based on PVDF/[Emim][NTf2] blend owned high sensitivity, fast response/recovery times, and low sensor response hysteresis [27]. Additionally, the good interaction between PVDF and [Bmim][PF6] provides permanent antistatic properties, which suitable for the production of anti-electrostatic films [55]. Moreover, the presence of [Emim][NTf2] improved the dispersion of MWCNTs in the PVDF matrix, which enhanced the electrical conductivity of the composites, and resulted in better electromagnetic interference shielding properties [48].

5. Conclusions

Two types of ionic liquids, blending processes of PVDF and PVDF-HFP blends, and mixing processes of PVDF and PVDF-HFP composites have been succinctly reviewed in this paper. The physicochemical properties, for instance, crystalline, mechanical, thermal, and chemical of the blends and composites have also been revisited in this succinct review. Hydrophilic and hydrophobic imidazolium-based ionic liquids are the two most significant ionic liquids utilized for the preparation of the blends and composites. The utilization of hydrophilic imidazolium-based ionic liquids can efficiently decrease the crystalline, mechanical, and thermal properties of the PVDF and PVDF-HFP blends and composites. On top of that, the utilization of hydrophobic imidazolium-based ionic liquids can effectively increase the mechanical and thermal properties of the blends and composites. In addition, the ionic liquids can form specific interactions with polymer matrices and fillers. The blends and composites can be applied in electronic and electric appliances, such as capacitors, polymer electrolytes, actuators, dielectric materials, sensor, etc. This succinct review may be useful for the preparation of PVDF and PVDF-HFP blends and composites by utilizing ionic liquids in the diversification of thermoplastic fluoropolymers functions for a multiplicity of applications.

Author Contributions

Conceptualization, A.A.S.; methodology, S.N.A.M.J.; validation, R.D.; formal analysis, S.N.A.M.J.; investigation, A.A.S.; resources, R.D.; data curation, S.N.A.M.J.; writing—original draft preparation, A.A.S.; writing—review and editing, S.N.A.M.J. and R.D.; project administration, A.A.S.; funding acquisition, A.A.S. and R.D. All authors have read and agreed to the published version of the manuscript.

Funding

This succinct review was funded by the Universiti Putra Malaysia under the Grant Putra IPM Scheme (project number: GP-IPM/2021/9697900).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Acknowledgments

The authors would like to thank Katherine M.E. Stewart from the Troy University for motivating the authors to write this succinct review.

Conflicts of Interest

The authors declare no conflict of interest. The funder had no role in the design of the review; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

References

  1. Stewart, K.M.E.; Hamilton, I.P.; Penlidis, A. Investigation of the Interaction between Benzene and SXFA Using DFT. Processes 2018, 6, 10. [Google Scholar] [CrossRef] [Green Version]
  2. Wang, X.; Xiao, C.; Liu, H.; Huang, Q.; Hao, J.; Fu, H. Poly (Vinylidene Fluoride-Hexafluoropropylene) Porous Membrane with Controllable Structure and Applications in Efficient Oil/Water Separation. Materials (Basel) 2018, 11, 443. [Google Scholar] [CrossRef] [Green Version]
  3. Shamsuri, A.A.; Abdan, K.; Kaneko, T. A Concise Review on the Physicochemical Properties of Biopolymer Blends Prepared in Ionic Liquids. Molecules 2021, 26, 216. [Google Scholar] [CrossRef]
  4. Shamsuri, A.A.; Jamil, S.N.A.M. Application of Quaternary Ammonium Compounds as Compatibilizers for Polymer Blends and Polymer Composites—A Concise Review. Appl. Sci. 2021, 11, 3167. [Google Scholar] [CrossRef]
  5. Shamsuri, A.A.; Md. Jamil, S.N.A.M. Compatibilization Effect of Ionic Liquid-Based Surfactants on Physicochemical Properties of PBS/Rice Starch Blends: An Initial Study. Materials (Basel) 2020, 13, 1885. [Google Scholar] [CrossRef] [Green Version]
  6. Shamsuri, A.A.; Jamil, S.N.A.M.; Abdan, K. Processes and Properties of Ionic Liquid-Modified Nanofiller/Polymer Nanocomposites—A Succinct Review. Processes 2021, 9, 480. [Google Scholar] [CrossRef]
  7. Shi, F.; Ma, Y.; Ma, J.; Wang, P.; Sun, W. Preparation and Characterization of PVDF/TiO2 Hybrid Membranes with Ionic Liquid Modified Nano-TiO2 Particles. J. Memb. Sci. 2013, 427, 259–269. [Google Scholar] [CrossRef]
  8. Mejri, R.; Dias, J.C.; Besbes Hentati, S.; Botelho, G.; Esperança, J.M.S.S.; Costa, C.M.; Lanceros-Mendez, S. Imidazolium-Based Ionic Liquid Type Dependence of the Bending Response of Polymer Actuators. Eur. Polym. J. 2016, 85, 445–451. [Google Scholar] [CrossRef]
  9. Mejri, R.; Dias, J.C.; Lopes, A.C.; Bebes Hentati, S.; Silva, M.M.; Botelho, G.; Mão De Ferro, A.; Esperança, J.M.S.S.; Maceiras, A.; Laza, J.M.; et al. Effect of Ionic Liquid Anion and Cation on the Physico-Chemical Properties of Poly (Vinylidene Fluoride)/Ionic Liquid Blends. Eur. Polym. J. 2015, 71, 304–313. [Google Scholar] [CrossRef]
  10. Thomas, E.; Parvathy, C.; Balachandran, N.; Bhuvaneswari, S.; Vijayalakshmi, K.P.; George, B.K. PVDF-Ionic Liquid Modified Clay Nanocomposites: Phase Changes and Shish-Kebab Structure. Polymer (Guildf) 2017, 115, 70–76. [Google Scholar] [CrossRef]
  11. Mejri, R.; Dias, J.C.; Hentati, S.B.; Martins, M.S.; Costa, C.M.; Lanceros-Mendez, S. Effect of Anion Type in the Performance of Ionic Liquid/Poly (Vinylidene Fluoride) Electromechanical Actuators. J. Non-Cryst. Solids 2016, 453, 8–15. [Google Scholar] [CrossRef] [Green Version]
  12. Xing, C.; Wang, Y.; Zhang, C.; Li, L.; Li, Y.; Li, J. Immobilization of Ionic Liquids onto the Poly (Vinylidene Fluoride) by Electron Beam Irradiation. Ind. Eng. Chem. Res. 2015, 54, 9351–9359. [Google Scholar] [CrossRef]
  13. Xing, C.; You, J.; Li, Y.; Li, J. Nanostructured Poly (Vinylidene Fluoride)/Ionic Liquid Composites: Formation of Organic Conductive Nanodomains in Polymer Matrix. J. Phys. Chem. C 2015, 119, 21155–21164. [Google Scholar] [CrossRef]
  14. Maity, N.; Mandal, A.; Nandi, A.K. Interface Engineering of Ionic Liquid Integrated Graphene in Poly (Vinylidene Fluoride) Matrix Yielding Magnificent Improvement in Mechanical, Electrical and Dielectric Properties. Polymer (Guildf) 2015, 65, 154–167. [Google Scholar] [CrossRef]
  15. Nath, A.K.; Kumar, A. Ionic Transport Properties of PVdF-HFP-MMT Intercalated Nanocomposite Electrolytes Based on Ionic Liquid, 1-Butyl-3-Methylimidazolium Bromide. Ionics (Kiel) 2013, 19, 1393–1403. [Google Scholar] [CrossRef]
  16. Nath, A.K.; Kumar, A. Swift Heavy Ion Irradiation Induced Enhancement in Electrochemical Properties of Ionic Liquid Based PVdF-HFP-Layered Silicate Nanocomposite Electrolyte Membranes. J. Memb. Sci. 2014, 453, 192–201. [Google Scholar] [CrossRef]
  17. Xu, P.; Gui, H.; Wang, X.; Hu, Y.; Ding, Y. Improved Dielectric Properties of Nanocomposites Based on Polyvinylidene Fluoride and Ionic Liquid-Functionalized Graphene. Compos. Sci. Technol. 2015, 117, 282–288. [Google Scholar] [CrossRef]
  18. Mandal, A.; Nandi, A.K. Ionic Liquid Integrated Multiwalled Carbon Nanotube in a Poly (Vinylidene Fluoride) Matrix: Formation of a Piezoelectric β-Polymorph with Significant Reinforcement and Conductivity Improvement. ACS Appl. Mater. Interfaces 2013, 5, 747–760. [Google Scholar] [CrossRef]
  19. Angaiah, S.; Murugadoss, V.; Arunachalam, S.; Panneerselvam, P.; Krishnan, S. Influence of Various Ionic Liquids Embedded Electrospun Polymer Membrane Electrolytes on the Photovoltaic Performance of DSSC. Eng. Sci. 2018, 12, 44–51. [Google Scholar] [CrossRef]
  20. Fan, L.Q.; Tu, Q.M.; Geng, C.L.; Wang, Y.L.; Sun, S.J.; Huang, Y.F.; Wu, J.H. Improved Redox-Active Ionic Liquid-Based Ionogel Electrolyte by Introducing Carbon Nanotubes for Application in All-Solid-State Supercapacitors. Int. J. Hydrog. Energy 2020, 45, 17131–17139. [Google Scholar] [CrossRef]
  21. Gomez-Coma, L.; Garea, A.; Rouch, J.C.; Savart, T.; Lahitte, J.F.; Remigy, J.C.; Irabien, A. Membrane Modules for CO2 Capture Based on PVDF Hollow Fibers with Ionic Liquids Immobilized. J. Memb. Sci. 2016, 498, 218–226. [Google Scholar] [CrossRef] [Green Version]
  22. Singh, P.K.; Sabin, K.C.; Chen, X. Ionic Liquid–Solid Polymer Electrolyte Blends for Supercapacitor Applications. Polym. Bull. 2016, 73, 255–263. [Google Scholar] [CrossRef]
  23. Che, Q.; Zhou, L.; Wang, J. Fabrication and Characterization of Phosphoric Acid Doped Imidazolium Ionic Liquid Polymer Composite Membranes. J. Mol. Liq. 2015, 206, 10–18. [Google Scholar] [CrossRef]
  24. Okada, D.; Kaneko, H.; Kato, K.; Furumi, S.; Takeguchi, M.; Yamamoto, Y. Colloidal Crystallization and Ionic Liquid Induced Partial β-Phase Transformation of Poly (Vinylidene Fluoride) Nanoparticles. Macromolecules 2015, 48, 2570–2575. [Google Scholar] [CrossRef]
  25. Wang, F.; Lack, A.; Xie, Z.; Frübing, P.; Taubert, A.; Gerhard, R. Ionic-Liquid-Induced Ferroelectric Polarization in Poly (Vinylidene Fluoride) Thin Films. Appl. Phys. Lett. 2012, 100, 062903. [Google Scholar] [CrossRef]
  26. Tuhania, P.; Singh, P.K.; Bhattacharya, B.; Dhapola, P.S.; Yadav, S.; Shukla, P.K.; Gupta, M. PVDF-HFP and 1-Ethyl-3-Methylimidazolium Thiocyanate–Doped Polymer Electrolyte for Efficient Supercapacitors. High Perform. Polym. 2018, 30, 911–917. [Google Scholar] [CrossRef]
  27. Kuberský, P.; Altšmíd, J.; Hamáček, A.; Nešpůrek, S.; Zmeškal, O. An Electrochemical NO2 Sensor Based on Ionic Liquid: Influence of the Morphology of the Polymer Electrolyte on Sensor Sensitivity. Sensors (Switzerland) 2015, 15, 28421–28434. [Google Scholar] [CrossRef]
  28. Lopes, A.C.; Gutiérrez, J.; Barandiarán, J.M. Direct Fabrication of a 3D-Shape Film of Polyvinylidene Fluoride (PVDF) in the Piezoelectric β-Phase for Sensor and Actuator Applications. Eur. Polym. J. 2018, 99, 111–116. [Google Scholar] [CrossRef]
  29. Sarkar, R.; Kundu, T.K. Density Functional Theory Studies on PVDF/Ionic Liquid Composite Systems. J. Chem. Sci. 2018, 130, 1–18. [Google Scholar] [CrossRef] [Green Version]
  30. Yu, Y.; Guo, J.; Sun, L.; Zhang, X.; Zhao, Y. Microfluidic Generation of Microsprings with Ionic Liquid Encapsulation for Flexible Electronics. Research 2019, 2019, 1–9. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  31. Guo, D.; Han, Y.; Huang, J.; Meng, E.; Ma, L.; Zhang, H.; Ding, Y. Hydrophilic Poly (Vinylidene Fluoride) Film with Enhanced Inner Channels for Both Water- and Ionic Liquid-Driven Ion-Exchange Polymer Metal Composite Actuators. ACS Appl. Mater. Interfaces 2019, 11, 2386–2397. [Google Scholar] [CrossRef]
  32. Feng, L.; Wang, K.; Zhang, X.; Sun, X.; Li, C.; Ge, X.; Ma, Y. Flexible Solid-State Supercapacitors with Enhanced Performance from Hierarchically Graphene Nanocomposite Electrodes and Ionic Liquid Incorporated Gel Polymer Electrolyte. Adv. Funct. Mater. 2018, 28, 1–9. [Google Scholar] [CrossRef]
  33. Zhu, Y.; Li, C.; Na, B.; Lv, R.; Chen, B.; Zhu, J. Polar Phase Formation and Competition in the Melt Crystallization of Poly (Vinylidene Fluoride) Containing an Ionic Liquid. Mater. Chem. Phys. 2014, 144, 194–198. [Google Scholar] [CrossRef]
  34. Chaurasia, S.K.; Singh, R.K. Crystallization Behaviour of a Polymeric Membrane Based on the Polymer PVdF-HFP and the Ionic Liquid BMIMBF4. RSC Adv. 2014, 4, 50914–50924. [Google Scholar] [CrossRef]
  35. Chaurasia, S.K.; Singh, R.K.; Chandra, S. Thermal Stability, Complexing Behavior, and Ionic Transport of Polymeric Gel Membranes Based on Polymer PVdF-HFP and Ionic Liquid, [BMIM][BF4]. J. Phys. Chem. B 2013, 117, 897–906. [Google Scholar] [CrossRef]
  36. Das, S.; Ghosh, A. Solid Polymer Electrolyte Based on PVDF-HFP and Ionic Liquid Embedded with TiO 2 Nanoparticle for Electric Double Layer Capacitor (EDLC) Application. J. Electrochem. Soc. 2017, 164, F1348–F1353. [Google Scholar] [CrossRef]
  37. Pandey, G.P.; Liu, T.; Hancock, C.; Li, Y.; Sun, X.S.; Li, J. Thermostable Gel Polymer Electrolyte Based on Succinonitrile and Ionic Liquid for High-Performance Solid-State Supercapacitors. J. Power Sources 2016, 328, 510–519. [Google Scholar] [CrossRef] [Green Version]
  38. Guan, J.; Xing, C.; Wang, Y.; Li, Y.; Li, J. Poly (Vinylidene Fluoride) Dielectric Composites with Both Ionic Nanoclusters and Well Dispersed Graphene Oxide. Compos. Sci. Technol. 2017, 138, 98–105. [Google Scholar] [CrossRef]
  39. Wang, Y.; Xing, C.; Guan, J.; Li, Y. Towards Flexible Dielectric Materials with High Dielectric Constant and Low Loss: PVDF Nanocomposites with Both Homogenously Dispersed CNTs and Ionic Liquids Nanodomains. Polymers (Basel) 2017, 9, 562. [Google Scholar] [CrossRef] [Green Version]
  40. Suleman, M.; Kumar, Y.; Hashmi, S.A. Structural and Electrochemical Properties of Succinonitrile-Based Gel Polymer Electrolytes: Role of Ionic Liquid Addition. J. Phys. Chem. B 2013, 117, 7436–7443. [Google Scholar] [CrossRef]
  41. Correia, D.M.; Barbosa, J.C.; Costa, C.M.; Reis, P.M.; Esperança, J.M.S.S.; De Zea Bermudez, V.; Lanceros-Méndez, S. Ionic Liquid Cation Size-Dependent Electromechanical Response of Ionic Liquid/Poly (Vinylidene Fluoride)-Based Soft Actuators. J. Phys. Chem. C 2019, 123, 12744–12752. [Google Scholar] [CrossRef]
  42. Correia, D.M.; Sabater i Serra, R.; Gómez Tejedor, J.A.; de Zea Bermudez, V.; Andrio Balado, A.; Meseguer-Dueñas, J.M.; Gomez Ribelles, J.L.; Lanceros-Méndez, S.; Costa, C.M. Ionic and Conformational Mobility in Poly (Vinylidene Fluoride)/Ionic Liquid Blends: Dielectric and Electrical Conductivity Behavior. Polymer (Guildf) 2018, 143, 164–172. [Google Scholar] [CrossRef]
  43. Dias, J.C.; Lopes, A.C.; Magalhães, B.; Botelho, G.; Silva, M.M.; Esperança, J.M.S.S.; Lanceros-Mendez, S. High Performance Electromechanical Actuators Based on Ionic Liquid/Poly (Vinylidene Fluoride). Polym. Test. 2015, 48, 199–205. [Google Scholar] [CrossRef]
  44. Dias, J.C.; Correia, D.C.; Lopes, A.C.; Ribeiro, S.; Ribeiro, C.; Sencadas, V.; Botelho, G.; Esperança, J.M.S.S.; Laza, J.M.; Vilas, J.L.; et al. Development of Poly (Vinylidene Fluoride)/Ionic Liquid Electrospun Fibers for Tissue Engineering Applications. J. Mater. Sci. 2016, 51, 4442–4450. [Google Scholar] [CrossRef]
  45. Yuan, C.; Zhu, X.; Su, L.; Yang, D.; Wang, Y.; Yang, K.; Cheng, X. Preparation and Characterization of a Novel Ionic Conducting Foam-Type Polymeric Gel Based on Polymer PVdF-HFP and Ionic Liquid [EMIM][TFSI]. Colloid Polym. Sci. 2015, 293, 1945–1952. [Google Scholar] [CrossRef]
  46. Zhang, X.; Kar, M.; Mendes, T.C.; Wu, Y.; MacFarlane, D.R. Supported Ionic Liquid Gel Membrane Electrolytes for Flexible Supercapacitors. Adv. Energy Mater. 2018, 8, 1702702. [Google Scholar] [CrossRef]
  47. Dias, J.C.; Correia, D.M.; Costa, C.M.; Ribeiro, C.; Maceiras, A.; Vilas, J.L.; Botelho, G.; de Zea Bermudez, V.; Lanceros-Mendez, S. Improved Response of Ionic Liquid-Based Bending Actuators by Tailored Interaction with the Polar Fluorinated Polymer Matrix. Electrochim. Acta 2019, 296, 598–607. [Google Scholar] [CrossRef]
  48. Sharma, M.; Sharma, S.; Abraham, J.; Thomas, S. Flexible EMI Shielding Materials Derived by Melt Blending PVDF and Ionic Liquid Modified MWNTs. Mater. Res. Express 2014, 1, 035003. [Google Scholar] [CrossRef] [Green Version]
  49. Jindaratsamee, P.; Ito, A.; Komuro, S.; Shimoyama, Y. Separation of CO 2 from the CO 2/N 2 Mixed Gas through Ionic Liquid Membranes at the High Feed Concentration. J. Memb. Sci. 2012, 423–424, 27–32. [Google Scholar] [CrossRef]
  50. Singh, R.; Bhattacharya, B.; Gupta, M.; Rahul; Khan, Z.H.; Tomar, S.K.; Singh, V.; Singh, P.K. Electrical and Structural Properties of Ionic Liquid Doped Polymer Gel Electrolyte for Dual Energy Storage Devices. Int. J. Hydrog. Energy 2017, 42, 14602–14607. [Google Scholar] [CrossRef]
  51. Hwang, S.K.; Park, T.J.; Kim, K.L.; Cho, S.M.; Jeong, B.J.; Park, C. Organic One-Transistor-Type Nonvolatile Memory Gated with Thin Ionic Liquid-Polymer Film for Low Voltage Operation. ACS Appl. Mater. Interfaces 2014, 6, 20179–20187. [Google Scholar] [CrossRef]
  52. Ortega, P.F.R.; Trigueiro, J.P.C.; Silva, G.G.; Lavall, R.L. Improving Supercapacitor Capacitance by Using a Novel Gel Nanocomposite Polymer Electrolyte Based on Nanostructured SiO2, PVDF and Imidazolium Ionic Liquid. Electrochim. Acta 2016, 188, 809–817. [Google Scholar] [CrossRef]
  53. Pandey, G.P.; Hashmi, S.A. Performance of Solid-State Supercapacitors with Ionic Liquid 1-Ethyl-3-Methylimidazolium Tris (Pentafluoroethyl) Trifluorophosphate Based Gel Polymer Electrolyte and Modified MWCNT Electrodes. Electrochim. Acta 2013, 105, 333–341. [Google Scholar] [CrossRef]
  54. Xing, C.; Guan, J.; Li, Y.; Li, J. Effect of a Room-Temperature Ionic Liquid on the Structure and Properties of Electrospun Poly (Vinylidene Fluoride) Nanofibers. ACS Appl. Mater. Interfaces 2014, 6, 4447–4457. [Google Scholar] [CrossRef] [PubMed]
  55. Xing, C.; Zhao, M.; Zhao, L.; You, J.; Cao, X.; Li, Y. Ionic Liquid Modified Poly (Vinylidene Fluoride): Crystalline Structures, Miscibility, and Physical Properties. Polym. Chem. 2013, 4, 5726–5734. [Google Scholar] [CrossRef]
  56. Ke, K.; Po, P.; Gao, S.; Voit, B. An Ionic Liquid as Interface Linker for Tuning Piezoresistive Sensitivity and Toughness in Poly (Vinylidene Fluoride)/Carbon Nanotube Composites. ACS Appl. Mater. Interfaces 2017, 9, 5437–5446. [Google Scholar] [CrossRef] [PubMed]
  57. Xing, C.; Zhao, L.; You, J.; Dong, W.; Cao, X.; Li, Y. Impact of Ionic Liquid-Modified Multiwalled Carbon Nanotubes on the Crystallization Behavior of Poly (Vinylidene Fluoride). J. Phys. Chem. B 2012, 116, 8312–8320. [Google Scholar] [CrossRef] [PubMed]
  58. Zhang, H.; Chen, Y.; Xiao, J.; Song, F.; Wang, C.; Wang, H. Fabrication of Enhanced Dielectric PVDF Nanocomposite Based on the Conjugated Synergistic Effect of Ionic Liquid and Graphene. Mater. Today Proc. 2019, 16, 1512–1517. [Google Scholar] [CrossRef]
  59. Xu, P.; Fu, W.; Luo, X.; Ding, Y. Enhanced Dc Conductivity and Conductivity Relaxation in PVDF/Ionic Liquid Composites. Mater. Lett. 2017, 206, 60–63. [Google Scholar] [CrossRef]
  60. Chen, H.Z.; Li, P.; Chung, T.S. PVDF/Ionic Liquid Polymer Blends with Superior Separation Performance for Removing CO2 from Hydrogen and Flue Gas. Int. J. Hydrog. Energy 2012, 37, 11796–11804. [Google Scholar] [CrossRef]
  61. Pandey, G.P.; Hashmi, S.A. Ionic Liquid 1-Ethyl-3-Methylimidazolium Tetracyanoborate-Based Gel Polymer Electrolyte for Electrochemical Capacitors. J. Mater. Chem. A 2013, 1, 3372–3378. [Google Scholar] [CrossRef]
  62. Shamsuri, A.A.; Daik, R. Mechanical and Thermal Properties of Nylon-6/LNR/MMT Nanocomposites Prepared through Emulsion Dispersion Technique. J. Adv. Res. Fluid Mech. Therm. Sci. 2020, 73, 1–12. [Google Scholar] [CrossRef]
  63. Shamsuri, A.A.; Md. Jamil, S.N.A.M. A Short Review on the Effect of Surfactants on the Mechanico-Thermal Properties of Polymer Nanocomposites. Appl. Sci. 2020, 10, 4867–4882. [Google Scholar] [CrossRef]
  64. Shamsuri, A.A.; Md. Jamil, S.N.A.M. Functional Properties of Biopolymer-Based Films Modified with Surfactants: A Brief Review. Processes 2020, 8, 1039. [Google Scholar] [CrossRef]
Processes 09 00761 g001 550
Figure 1. Schematic of the polymerization of vinylidene fluoride to make PVDF.
Figure 1. Schematic of the polymerization of vinylidene fluoride to make PVDF.
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Figure 2. Schematic of the copolymerization of vinylidene fluoride with hexafluoropropylene to make PVDF-HFP.
Figure 2. Schematic of the copolymerization of vinylidene fluoride with hexafluoropropylene to make PVDF-HFP.
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Figure 3. Chemical structures of hydrophilic imidazolium-based ionic liquids and the abbreviations are explained in Table 1.
Figure 3. Chemical structures of hydrophilic imidazolium-based ionic liquids and the abbreviations are explained in Table 1.
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Figure 4. Chemical structures of hydrophobic imidazolium-based ionic liquids and the abbreviations are explained in Table 2.
Figure 4. Chemical structures of hydrophobic imidazolium-based ionic liquids and the abbreviations are explained in Table 2.
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Table
Table 1. Examples of hydrophilic imidazolium-based ionic liquids utilized for preparation of PVDF and PVDF-HFP blends and composites.
Table 1. Examples of hydrophilic imidazolium-based ionic liquids utilized for preparation of PVDF and PVDF-HFP blends and composites.
Hydrophilic Imidazolium-Based Ionic LiquidAbbreviationReferences
1-Methyl-3-carboxymethylimidazolium chloride[Mcmim][Cl][7]
1-Ethyl-3-methylimidazolium chloride[Emim][Cl][8,9]
1-Butyl-3-methylimidazolium chloride[Bmim][Cl][10]
1-Hexyl-3-methylimidazolium chloride[Hmim][Cl][8,9,11]
1-Decyl-3-methylimidazolium chloride[Dmim][Cl][8,9]
1-Vinyl-3-butylimidazolium chloride[Vbim][Cl][12,13]
1-(2-Amino-ethyl)-3-methylimidazolium bromide[Aemim][Br][14]
1-Butyl-3-methylimidazolium bromide[Bmim][Br][15,16]
1-Hexadecyl-3-methylimidazolium bromide[Hdmim][Br][17]
3-Aminoethylimidazolium bromide[Aeim][Br][18]
1,3-Dimethylimidazolium iodide[Mmim][I][19]
1-Propyl-3-methylimidazolium iodide[Pmim][I][19]
1-Butyl-3-methylimidazolium iodide[Bmim][I][19,20]
1-Hexyl-3-methylimidazolium iodide[Hmim][I][19]
1-Ethyl-3-methylimidazolium acetate[Emim][OAc][21]
1-Ethyl-3-methylimidazolium dicyanamide[Emim][DCA][22]
1-Butyl-3-methylimidazolium dihydrogenphosphate[Bmim][H2PO4][23]
1-Ethyl-3-methylimidazolium ethylsulfate[Emim][EtSO4][21]
1-Ethyl-3-methylimidazolium nitrate[Emim][NO3][24,25]
1-Ethyl-3-methylimidazolium thiocyanate[Emim][SCN][26]
1-Ethyl-3-methylimidazolium tetrafluoroborate[Emim][BF4][27,28,29,30,31,32]
1-Butyl-3-methylimidazolium tetrafluoroborate[Bmim][BF4][29,33,34,35,36,37]
1-Vinyl-3-ethylimidazolium tetrafluoroborate[Veim][BF4][38,39]
1-Ethyl-3-methylimidazolium trifluoromethanesulfonate[Emim][CF3SO3][40]
1-Butyl-3-methylimidazolium trifluoromethanesulfonate[Bmim][CF3SO3][27]
Table
Table 2. Examples of hydrophobic imidazolium-based ionic liquids utilized for preparation of PVDF and PVDF-HFP blends and composites.
Table 2. Examples of hydrophobic imidazolium-based ionic liquids utilized for preparation of PVDF and PVDF-HFP blends and composites.
Hydrophobic Imidazolium-Based Ionic LiquidAbbreviationReferences
1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide[Emim][NTf2][8,9,27,41,42,43,44,45,46,47,48]
1-Ethyl-3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide[Emmim][NTf2][41]
1-Propyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide[Pmim][NTf2][41]
1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide[Bmim][NTf2][49]
1-Hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide[Hmim][NTf2][8,9,11]
1-Decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide[Dmim][NTf2][8,9]
1,2-Dimethyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide[Mmpim][NTf2][50]
1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide[Emim][TFSA][51]
1-Ethyl-3-methylimidazolium bis(fluorosulfonyl)imide[Emim][FSI][52]
1-Ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate[Emim][FAP][53]
1-Hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate[Hmim][FAP][27]
1-Butyl-3-methylimidazolium hexafluorophosphate[Bmim][PF6][23,49,54,55,56,57,58]
1-Benzyl-3-methylimidazolium hexafluorophosphate[Bzmim][PF6][59]
1-Ethyl-3-methylimidazolium tetracyanoborate[Emim][B(CN)4][60,61]
1-Hexyl-3-methylimidazolium tetrafluoroborate[Hmim][BF4][29]
Table
Table 3. Examples of fillers modified with imidazolium-based ionic liquids for preparation of PVDF and PVDF-HFP composites.
Table 3. Examples of fillers modified with imidazolium-based ionic liquids for preparation of PVDF and PVDF-HFP composites.
FillerAbbreviationReferences
GrapheneGr[17,58]
Graphene oxideGO[32,38]
Carboxylated graphene oxideGO-COOH[14]
Multi-walled carbon nanotubesMWCNTs[20,39,48,57]
Carboxylated multi-walled carbon nanotubesMWCNT-COOH[18,56]
Sodium montmorilloniteNaMMT[10]
Octadecylamine modified montmorilloniteOMMT[15,16]
Silicon dioxideSiO2[52]
Titanium dioxideTiO2[7,36]
Polyvinyl pyrrolidone grainsPVP grains[31]
SuccinonitrileSN[37,40]
Table
Table 4. Types of polymer matrices, hydrophilic imidazolium-based ionic liquids, and preparation processes of PVDF and PVDF-HFP blends.
Table 4. Types of polymer matrices, hydrophilic imidazolium-based ionic liquids, and preparation processes of PVDF and PVDF-HFP blends.
Polymer MatrixHydrophilic Ionic LiquidBlending ProcessBlending Temp. (°C)Time (Hour)Final ProcessFinal Temp. (°C)Time (Hour)References
PVDF[Emim][Cl]SBR3SC2100.17[8,9]
PVDF[Hmim][Cl]SBR3SC2000.17[8,9,11]
PVDF[Dmim][Cl]SBR3SC2100.17[8,9]
PVDF[Vbim][Cl]MB1900.12HP2100.17[12,13]
PVDF[Emim][OAc]LIR48UUU[21]
PVDF[Emim][EtSO4]LIR48UUU[21]
PVDF[Emim][NO3]SBRUS-C10024[24,25]
PVDF[Bmim][H2PO4]SB506SC12024[23]
PVDF[Bmim][CF3SO3]SB80USC2524[27]
PVDF[Emim][BF4]SBRUMGRU[27,28,29,30]
PVDF[Bmim][BF4]SB60USC60U[29,33]
PVDF-HFP[Mmim][I]SR24UUU[19]
PVDF-HFP[Pmim][I]SR24UUU[19]
PVDF-HFP[Bmim][I]SR24UUU[19]
PVDF-HFP[Hmim][I]SR24UUU[19]
PVDF-HFP[Emim][DCA]SB60USCRU[22]
PVDF-HFP[Emim][SCN]SBR12SCRU[26]
PVDF-HFP[Bmim][BF4]SB506SCRU[34,35]
SB = solution blending, MB = melt blending, LI = liquid impregnation, S = soaking, SC = solution casting, HP = hot pressing, S-C = spin-coating, MG = microfluidic generation, R = room, and U = unstated.
Table
Table 5. Types of polymer matrices, hydrophobic imidazolium-based ionic liquids, and preparation processes of PVDF and PVDF-HFP blends.
Table 5. Types of polymer matrices, hydrophobic imidazolium-based ionic liquids, and preparation processes of PVDF and PVDF-HFP blends.
Polymer MatrixHydrophobic Ionic LiquidBlending ProcessBlending Temp. (°C)Time (Hour)Final ProcessFinal Temp. (°C)Time (Hour)References
PVDF[Emim][NTf2]SBR3SC2100.17[8,9,27,41,42,43,44]
PVDF[Emmim][NTf2]SBRUSC2100.17[41]
PVDF[Pmim][NTf2]SBRUSC2100.17[41]
PVDF[Bmim][NTf2]LIR0.5UUU[49]
PVDF[Hmim][NTf2]SBR3SC2100.17[8,9,11]
PVDF[Dmim][NTf2]SBR3SC2100.17[8,9]
PVDF[Emim][B(CN)4]SBR2SC5024[60]
PVDF[Bmim][PF6]SB506SC12024[23,49,54,55]
PVDF[Bzmim][PF6]SBRUHP175U[59]
PVDF[Hmim][FAP]SB80USC2524[27]
PVDF-HFP[Emim][NTf2]SB5012SCRU[45,46,47]
PVDF-HFP[Mmpim][NTf2]SBR4SCRU[50]
PVDF-HFP[Emim][TFSA]SBRUS-CR0.02[51]
PVDF-HFP[Emim][FAP]SBR12SCRU[53]
PVDF-HFP[Emim][B(CN)4]SBR12SCRU[61]
SB = solution blending, LI = liquid impregnation, SC = solution casting, HP = hot pressing, S-C = spin-coating, R = room, and U = unstated.
Table
Table 6. Types of polymer matrices, fillers, imidazolium-based ionic liquids, and preparation processes of PVDF and PVDF-HFP composites.
Table 6. Types of polymer matrices, fillers, imidazolium-based ionic liquids, and preparation processes of PVDF and PVDF-HFP composites.
Polymer MatrixFillerIonic LiquidMixing ProcessMixing Temp. (°C)Time (Hour)Final ProcessFinal Temp. (°C)Time (Hour)References
PVDFGr[Hdmim][Br]UlR0.17HP190U[17]
PVDFGr[Bmim][PF6]MB200UUUU[58]
PVDFGO[Veim][BF4]SBRUHP2000.05[38]
PVDFGO-COOH[Aemim][Br]UlRUSC6048[14]
PVDFMWCNT-COOH[Aeim][Br]SoR0.17SC7072[18]
PVDFMWCNTs[Veim][BF4]MB190UHP190U[39]
PVDFMWCNTs[Emim][NTf2]MB2200.33CMUU[48]
PVDFMWCNTs[Bmim][PF6]MB1900.08HP200U[57]
PVDFMWCNT-COOH[Bmim][PF6]MB2100.25CM220U[56]
PVDFNaMMT[Bmim][Cl]SBR24SC1002[10]
PVDFSiO2[Emim][FSI]SoR2SC13024[52]
PVDFTiO2[Mcmim][Cl]SB2004HP200U[7]
PVDFPVP grains[Emim][BF4]SBRUSRU[31]
PVDF-HFPGO[Emim][BF4]SB50USCR12[32]
PVDF-HFPMWCNTs[Bmim][I]SB602SC8012[20]
PVDF-HFPOMMT[Bmim][Br]UlR0.5SR5[15,16]
PVDF-HFPTiO2[Bmim][BF4]SoR2SC9024[36]
PVDF-HFPSN[Bmim][BF4]SBR10SCRU[37]
PVDF-HFPSN[Emim][CF3SO3]SBR24SCRU[40]
Ul = ultrasonication, MB = melt blending, SB = solution blending, So = sonication, HP = hot pressing, SC = solution casting, CM = compression molding, S = soaking, R = room, and U = unstated.
Table
Table 7. Physicochemical properties of PVDF/and PVDF-HFP/hydrophilic imidazolium-based ionic liquid blends and composites.
Table 7. Physicochemical properties of PVDF/and PVDF-HFP/hydrophilic imidazolium-based ionic liquid blends and composites.
Blend|CompositeHydrophilic Ionic LiquidPhysicochemical Properties *References
CrystallineMechanicalThermalChemical
PVDF[Emim][Cl]▼▼▼▲[9]
PVDF-HFP[Bmim][BF4]▼n/a▼▲[35]
PVDF/MWCNT-COOH[Aeim][Br]▼▲
▲		▲▲[18]
PVDF/PVP grains[Emim][BF4]▼▼▼▲[31]
PVDF-HFP/OMMT[Bmim][Br]▼n/a▼▲[15]
PVDF-HFP/SN[Emim][CF3SO3]▼n/a▲
▲		▲[40]
* The symbol ‘▲’ corresponds to an increase in the properties and ‘▼’ a decrease in the properties while ‘n/a’ describes not available.
Table
Table 8. Physicochemical properties of PVDF/and PVDF-HFP/hydrophobic imidazolium-based ionic liquid blends and composites.
Table 8. Physicochemical properties of PVDF/and PVDF-HFP/hydrophobic imidazolium-based ionic liquid blends and composites.
Blend|CompositeHydrophobic Ionic LiquidPhysicochemical Properties *References
CrystallineMechanicalThermalChemical
PVDF[Emim][NTf2]▼▼▼▲[43]
PVDF[Bmim][PF6]▼▲
▲		▲
▲		▲[55]
PVDF-HFP[Emim][NTf2]▼▼▼▲[47]
PVDF/MWCNTs[Emim][NTf2]▼▲▲▲[48]
PVDF/MWCNTs[Bmim][PF6]▼n/a▲
▲		▲[57]
PVDF/MWCNT-COOH[Bmim][PF6]▼▲
▲		n/a▲[56]
* The symbol ‘▲’ corresponds to an increase in the properties and ‘▼’ a decrease in the properties while ‘n/a’ describes not available.
Table
Table 9. Applications of PVDF/and PVDF-HFP/hydrophilic imidazolium-based ionic liquid blends and composites.
Table 9. Applications of PVDF/and PVDF-HFP/hydrophilic imidazolium-based ionic liquid blends and composites.
Blend|CompositeApplicationReferences
PVDF/[Hmim][Cl]Electromechanical actuators[9,11]
PVDF/[Vbim][Cl]Superthin dielectric capacitors[12,13]
PVDF/[Emim][OAc]Carbon dioxide capture fibers[21]
PVDF/[Emim][EtSO4]Carbon dioxide capture fibers[21]
PVDF/[Bmim][H2PO4]Proton exchange membranes[23]
PVDF/[Emim][BF4]Flexible electronics[30]
PVDF-HFP/[Bmim][I]Polymer electrolyte membranes[19]
PVDF-HFP/[Emim][DCA]Electrochemical double-layer capacitors[22]
PVDF-HFP/[Emim][SCN]Electrochemical double-layer capacitors[26]
PVDF-HFP/[Bmim][BF4]Polymer electrolyte membranes[34,35]
PVDF/Gr/[Hdmim][Br]High-charge storage capacitors[17]
PVDF/GO/[Veim][BF4]Polymeric dielectric composites[38]
PVDF/MWCNTs/[Veim][BF4]Flexible dielectric materials[39]
PVDF/TiO2/[Mcmim][Cl]Antifouling membranes[7]
PVDF/PVP grains/[Emim][BF4]Flexible actuators[31]
PVDF-HFP/GO/[Emim][BF4]Flexible solid-state supercapacitors[32]
PVDF-HFP/MWCNTs/[Bmim][I]All-solid-state supercapacitors[20]
PVDF-HFP/OMMT/[Bmim][Br]Composite electrolyte membranes[15,16]
PVDF-HFP/TiO2/[Bmim][BF4]Electrochemical double-layer capacitors[36]
PVDF-HFP/SN/[Bmim][BF4]Solid-state supercapacitors[37]
PVDF-HFP/SN/[Emim][CF3SO3]Electrochemical double-layer capacitors[40]
Table
Table 10. Applications of PVDF/and PVDF-HFP/hydrophobic imidazolium-based ionic liquid blends and composites.
Table 10. Applications of PVDF/and PVDF-HFP/hydrophobic imidazolium-based ionic liquid blends and composites.
Blend|CompositeApplicationReferences
PVDF/[Emim][NTf2]Electromechanical actuators[8,9]
PVDF/[Emim][NTf2]Nitrogen dioxide sensor[27]
PVDF/[Pmim][NTf2]Electromechanical actuators[41]
PVDF/[Bmim][NTf2]Carbon dioxide separation membranes[49]
PVDF/[Emim][B(CN)4]Carbon dioxide separation membranes[60]
PVDF/[Bmim][PF6]Carbon dioxide separation membranes[49]
PVDF/[Bmim][PF6]Transparent anti-electrostatic films[55]
PVDF/[Bzmim][PF6]Solid polymer-based electrolytes[59]
PVDF/[Hmim][FAP]Nitrogen dioxide sensor[27]
PVDF-HFP/[Emim][NTf2]Flexible supercapacitors[46]
PVDF-HFP/[Emim][NTf2]Composite bending actuators[47]
PVDF-HFP/[Mmpim][NTf2]Polymer electrolyte films[50]
PVDF-HFP/[Emim][TFSA]Flexible organic memory[51]
PVDF-HFP/[Emim][FAP]Electrochemical double-layer capacitors[53]
PVDF-HFP/[Emim][B(CN)4]Electrochemical double-layer capacitors[61]
PVDF/Gr/[Bmim][PF6]Flexible dielectric materials[58]
PVDF/MWCNTs/[Emim][NTf2]Electromagnetic interference shielding materials[48]
PVDF/SiO2/[Emim][FSI]Solid supercapacitors[52]
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Shamsuri, A.A.; Daik, R.; Md. Jamil, S.N.A. A Succinct Review on the PVDF/Imidazolium-Based Ionic Liquid Blends and Composites: Preparations, Properties, and Applications. Processes 2021, 9, 761. https://doi.org/10.3390/pr9050761

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Shamsuri AA, Daik R, Md. Jamil SNA. A Succinct Review on the PVDF/Imidazolium-Based Ionic Liquid Blends and Composites: Preparations, Properties, and Applications. Processes. 2021; 9(5):761. https://doi.org/10.3390/pr9050761

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Shamsuri, Ahmad Adlie, Rusli Daik, and Siti Nurul Ain Md. Jamil. 2021. "A Succinct Review on the PVDF/Imidazolium-Based Ionic Liquid Blends and Composites: Preparations, Properties, and Applications" Processes 9, no. 5: 761. https://doi.org/10.3390/pr9050761

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