**2.3 ILs as additives for physical processing of HPPs**

The application of ILs for HPPs is not limited to their use as reaction media in polymerisations for preparing HPPs, and ILs are miscible with some HPPs and used as additives in the materials such as the components of polymer materials, plasticizers, and porogenic agents. By blending ILs with HPPs, the properties of the obtained mixtures can be considerably affected [56]. Thus, applications of ILs are being explored in the fields of membranes, microcapsules, electrolytes, NCs and grease.

#### *2.3.1 Membrane*

Supported IL materials have two main processes. First, ILs are covalently linked to polymers, inorganic surfaces or particles, thereby supporting the IL materials. In such systems, the properties of the ILs are modified to some extent, but generally,

the main features are retained. Second, ILs are dissolved and imbibed in a polymeric membrane, porous matrix, particle or bulk material as the components of the mixture, and the properties of the IL are retained [57]. In recent years, supported IL membranes (SILMs) have received considerable attention for their applications in gas separation, electrolyte, proton exchange, etc.

Early on, it was reported that ILs based on 1-*n*-alkyl-3-methylimidazolium cation (*n*-butyl, *n*-octyl, and *n*-decyl) can be used together with the anions PF6 <sup>−</sup> or BF4 <sup>−</sup>. Immobilisation of these ILs on a polyvinylidene fluoride (PVDF) membrane provides an extremely highly selective transport for secondary amines over tertiary amines [58]. Later, the PVDF/ILs composite membranes were prepared. A membrane using [emim][Tf2N] and PVDF hollow fibre was prepared as a support for CO2/N2 separation [59].

A quasi-solid-state dye-sensitised solar cell based on poly(vinylidenefluorideco-hexafluoro-propylene) P(VDF-HFP)/SBA-15 nanocomposite membranes was obtained using dimethyl-propylimidazolium iodide (DMPII) IL [60]. The SILM was prepared using a hydrophilic PVDF support immobilised in the IL 1-butyl-2,3-dimethylimidazolium hexafluorophosphate ([b*d*mim][PF6]) [61]. The preparation of PVDF-blended membranes with dominating β-phase crystals was studied in ILs 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4), [bmim][PF6] and 1-methylimidazolium trifluoromethanesulphonic ([mim]CF3SO3) as the co-solvents for zwitterionic copolymers [62]. A PVDF membrane with piezoelectric β-form was prepared by immersion precipitation in mixed solvents containing an IL [bmim] [BF4] [63]. Composite membranes were prepared as electroactive actuators using PVDF and [emim][Tf2N] as the plasticiser [64]. A 1-butyl-3-methylimidazolium triflate ([bmim]OTf)/PVDF composite membrane was prepared by the impregnation method and used for the separation of C6H6/H2 and C6H12/H2, as shown in **Figure 6** [65]. Thin films containing 1-ethyl-3-methylimidazolium nitrate ([emim] [NO3]) IL and PVDF were investigated [66]. Another HPP-containing fluorine, polytetrafluoroethylene (PTFE), was often prepared using an SILM. For example, gelled SILMs were synthesised by the gelation of [bmim][PF6] in the pores of PTFE hollow fibres and used in the separation of butanol from acetone-butanol-ethanol mixtures (ABE) by sweep gas pervaporation [67]. Amino-acid-IL-based-facilitated transport membranes containing PTFE were prepared via impregnation [68].

The SILMs prepared with PSF supports are often used for CO2 separation such as CO2/He, CO2/CH4 and CO2/N2 separation, even at elevated temperatures [69–71]. In addition, ion-conductive membranes were prepared by casting a solution of Udel-type PSF and IL 1-butyl-3-methylimidazolium trifluoromethane-sulphonate ([bmim][TfO]) or 1-ethylimidazolium trifluoromethanesulphonate ([eim][TfO]) [72]. The SILMs prepared with PES supports are frequently used in the separation of gases, especially SO2 [73, 74] and CO2 [75–78]. In addition, PES membranes with ion exchange and anti-biofouling properties were prepared by the surface immobilisation of Brønsted acidic ILs via double-click reactions [79]. A sulphonated PES (SPES) film containing ILs was obtained by solution casting and prepared using double-side, self-cleaning polymeric materials, as shown in **Figure 7** [80]. Hydrophilic porous PES membranes and microcapsules were prepared via nonsolvent-induced phase separation (NIPS) using IL [bmim][PF6] as the structure control agent [81].

The surface wettability of negatively charged PI films was tuned by the electrostatic self-assembly of ILs and formation of spherical nanoparticles, indicating the assembly of longer-substituent cations [82]. The membranes containing ILs prepared with PI supports were often used in gas separation [83–86] and fuel cells [87–89]. In addition, available PAIs [90], copolymers of poly(ethylene glycol) (PEG) and aromatic PI [91, 92], and SPI [93–95] were also used in the preparation

**109**

ILs in the presence of Y2O3 [100].

*Picture and schematic of the final material.*

*impregnation (b and d) with [bmim] OTf.*

*2.3.2 Microcapsule*

**Figure 6.**

**Figure 7.**

*Progress in Ionic Liquids as Reaction Media, Monomers and Additives in High-Performance…*

of membranes containing ILs. For example, SPI/IL composite membranes as proton-exchange membranes have been reported in recent years [96, 97].

*Photographs (a and b) and SEM images (c and d) of the PVDF membrane before (a and c) and after* 

Composite membranes based on sulphonated poly(ether ether)ketone (SPEEK) with ILs [CH3CH2CH2NH3][CF3COO] (TFAPA), [bmim][Cl] and [bmim][PF6] have been prepared [98, 99]. Composite membranes have been prepared using SPEEK

In 2007, monodispersed microcapsules enclosing [bmim][PF6] were prepared via a two-stage microfluidic approach, as shown in **Figure 8**; the hollow PSF microcapsules showed an encapsulation capacity of 30.8% [101]. PSF microcapsules containing

*DOI: http://dx.doi.org/10.5772/intechopen.86472*

*Progress in Ionic Liquids as Reaction Media, Monomers and Additives in High-Performance… DOI: http://dx.doi.org/10.5772/intechopen.86472*

#### **Figure 6.**

*Solvents, Ionic Liquids and Solvent Effects*

BF4

CO2/N2 separation [59].

gas separation, electrolyte, proton exchange, etc.

the main features are retained. Second, ILs are dissolved and imbibed in a polymeric membrane, porous matrix, particle or bulk material as the components of the mixture, and the properties of the IL are retained [57]. In recent years, supported IL membranes (SILMs) have received considerable attention for their applications in

Early on, it was reported that ILs based on 1-*n*-alkyl-3-methylimidazolium cation (*n*-butyl, *n*-octyl, and *n*-decyl) can be used together with the anions PF6

<sup>−</sup>. Immobilisation of these ILs on a polyvinylidene fluoride (PVDF) membrane provides an extremely highly selective transport for secondary amines over tertiary amines [58]. Later, the PVDF/ILs composite membranes were prepared. A membrane using [emim][Tf2N] and PVDF hollow fibre was prepared as a support for

A quasi-solid-state dye-sensitised solar cell based on poly(vinylidenefluorideco-hexafluoro-propylene) P(VDF-HFP)/SBA-15 nanocomposite membranes was obtained using dimethyl-propylimidazolium iodide (DMPII) IL [60]. The SILM was prepared using a hydrophilic PVDF support immobilised in the IL 1-butyl-2,3-dimethylimidazolium hexafluorophosphate ([b*d*mim][PF6]) [61]. The preparation of PVDF-blended membranes with dominating β-phase crystals was studied in ILs 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4), [bmim][PF6] and 1-methylimidazolium trifluoromethanesulphonic ([mim]CF3SO3) as the co-solvents for zwitterionic copolymers [62]. A PVDF membrane with piezoelectric β-form was prepared by immersion precipitation in mixed solvents containing an IL [bmim] [BF4] [63]. Composite membranes were prepared as electroactive actuators using PVDF and [emim][Tf2N] as the plasticiser [64]. A 1-butyl-3-methylimidazolium triflate ([bmim]OTf)/PVDF composite membrane was prepared by the impregnation method and used for the separation of C6H6/H2 and C6H12/H2, as shown in **Figure 6** [65]. Thin films containing 1-ethyl-3-methylimidazolium nitrate ([emim] [NO3]) IL and PVDF were investigated [66]. Another HPP-containing fluorine, polytetrafluoroethylene (PTFE), was often prepared using an SILM. For example, gelled SILMs were synthesised by the gelation of [bmim][PF6] in the pores of PTFE hollow fibres and used in the separation of butanol from acetone-butanol-ethanol mixtures (ABE) by sweep gas pervaporation [67]. Amino-acid-IL-based-facilitated transport membranes containing PTFE were prepared via impregnation [68]. The SILMs prepared with PSF supports are often used for CO2 separation such as CO2/He, CO2/CH4 and CO2/N2 separation, even at elevated temperatures [69–71]. In addition, ion-conductive membranes were prepared by casting a solution of Udel-type PSF and IL 1-butyl-3-methylimidazolium trifluoromethane-sulphonate ([bmim][TfO]) or 1-ethylimidazolium trifluoromethanesulphonate ([eim][TfO]) [72]. The SILMs prepared with PES supports are frequently used in the separation of gases, especially SO2 [73, 74] and CO2 [75–78]. In addition, PES membranes with ion exchange and anti-biofouling properties were prepared by the surface immobilisation of Brønsted acidic ILs via double-click reactions [79]. A sulphonated PES (SPES) film containing ILs was obtained by solution casting and prepared using double-side, self-cleaning polymeric materials, as shown in **Figure 7** [80]. Hydrophilic porous PES membranes and microcapsules were prepared via nonsolvent-induced phase separation (NIPS) using IL [bmim][PF6] as the structure

The surface wettability of negatively charged PI films was tuned by the electrostatic self-assembly of ILs and formation of spherical nanoparticles, indicating the assembly of longer-substituent cations [82]. The membranes containing ILs prepared with PI supports were often used in gas separation [83–86] and fuel cells [87–89]. In addition, available PAIs [90], copolymers of poly(ethylene glycol) (PEG) and aromatic PI [91, 92], and SPI [93–95] were also used in the preparation

<sup>−</sup> or

**108**

control agent [81].

*Photographs (a and b) and SEM images (c and d) of the PVDF membrane before (a and c) and after impregnation (b and d) with [bmim] OTf.*

**Figure 7.** *Picture and schematic of the final material.*

of membranes containing ILs. For example, SPI/IL composite membranes as proton-exchange membranes have been reported in recent years [96, 97].

Composite membranes based on sulphonated poly(ether ether)ketone (SPEEK) with ILs [CH3CH2CH2NH3][CF3COO] (TFAPA), [bmim][Cl] and [bmim][PF6] have been prepared [98, 99]. Composite membranes have been prepared using SPEEK ILs in the presence of Y2O3 [100].

#### *2.3.2 Microcapsule*

In 2007, monodispersed microcapsules enclosing [bmim][PF6] were prepared via a two-stage microfluidic approach, as shown in **Figure 8**; the hollow PSF microcapsules showed an encapsulation capacity of 30.8% [101]. PSF microcapsules containing

#### **Figure 8.**

*Optical microscopic images and composition of organic phase is PSF: dichloromethane (DCM): [bmim] PF6 = 5 g: 80 ml: 3 g; continuous phase is 0.1 wt% gelatin solution; inner size of nozzle: 0.6 mm, IL microcapsules, flow rate of continuous phases (CP): 30 ml/min; and flow rate of droplet phases (DP): 125 μl/min.*

[bmim][PF6] were also obtained by spraying a suspension dispersion with an encapsulation capacity of 29% [102]. PSF microcapsules have practical use such as the removal of caprolactam from water [103]. PEEK microcapsules containing trihexyl(tetradecyl) phosphonium chloride IL was obtained in *N*,*N*-dimethylformamide (DMF) as the dispersing phase and dodecane [104]. PTFE microcapsules containing [hmim][Tf2N] IL lubricant with small sizes (below 10 μm) have been reported [105].
