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To investigate the effect of imidazolium ionic liquid with poly(ethylene glycol) segment (IL) on the polar phase crystallization behavior of poly(vinylidene fluoride) (PVDF), a series of PVDF/IL composites were prepared using solution-cast method. The crystallization peak temperature of PVDF composites and the growth speed of samples decrease with increasing of IL. The >CF 2 groups in amorphous region are retained and >CF 2 groups in crystalline region are liberated by the PEG long soft segments of IL. The intensity of peaks represented as α phase reduces, moreover polar phase content increases with increasing of IL. The interaction between the >CF 2 and the imidazolium cation can induce the polar phase, and the interaction between the >CF 2 and PEG soft segment can strengthen polar crystalline induction. PVDF/12IL composite can form big γ spherulite circled by β phase. [ABSTRACT FROM AUTHOR]

To investigate the effect of poly(ethylene glycol)-containing ionic liquid (IL) and thermal annealing treatment on crystallization and dielectric relaxation behavior of poly(vinylidene fluoride) (PVDF), a series of PVDF/IL composites have been prepared using a solution-cast method. The interaction between imidazolium cation of ILs and >CF 2 groups of PVDF can transfer nonpolar α phase to polar β and γ phase as a template at the primary crystallization, and then the interaction between PEG of ILs and >CF 2 groups of PVDF can facilitate the PVDF chains in amorphous region to bring more polar phase and decrease the degree of crystallization for PVDF composites according to the template under thermal annealing treatment. The experimental dielectric data were analyzed within the formalisms of complex permittivity and electric modulus. In the frequency spectra of PVDF composites, dc conductivity, electrode and Maxwell-Wagner-Sillars (MWS) interfacial polarization resulted in high values of dielectric permittivity. The incorporation of ILs into the matrix and thermal annealing treatment can accelerate dc conductivity. The temperature dependence of relaxation time of dc conductivity follows the Arrhenius equation. The effect of annealing treatment on charge carrier movement mechanism was resulted from the increase of ion mobility induced by polymer chain segmental motion and polar phase crystals. [ABSTRACT FROM AUTHOR]

To investigate the effects of 1-benzyl-3-methylimidazolium hexafluorophosphate on the crystal phase, morphology and dielectric relaxation behavior of poly(vinylidene fluoride) (PVDF), a series of PVDF/IL composites have been prepared using solution-cast method. The interaction between ILs and >CF 2 groups of PVDF can facilitate the PVDF chains in amorphous area to form more polar phase for PVDF composites. In the frequency spectra of PVDF composites, MWS interfacial polarization, electrode polarization and dc conductivity resulted in high values of dielectric permittivity. The incorporation of ILs into the matrix can accelerate dc conductivity. The effect of IL on charge carrier movement mechanism was resulted from the increase of ion mobility induced by polar phase crystal and ion concentration. [ABSTRACT FROM AUTHOR]

High temperature vulcanized silicone rubber (SR) based nanocomposites with carbon black (CB) and ionic liquid-modified carbon black (CB-IL) as fillers were fabricated using mechanical mixing method and their piezoresistive properties were carefully characterized. 1-hexadecyl-3-methylimidazolium bromide (IL) can improve the dispersibility of CB in SR matrix by morphology characterization. The CB-IL/SR composites showed a lower percolation threshold compared with CB/SR composites. The CB-IL/SR composite with 5 vol% content of CB-IL shows higher piezoresistivity, better repeatability and shorter relaxation time due to the plasticizing effect of IL. The results suggest that the CB-IL/SR composites provide a new route toward fabrication of flexible piezoresistive sensors and wearable electronic devices. [ABSTRACT FROM AUTHOR]

Polyvinylidene fluoride (PVDF) based nanocomposites with graphene and ionic liquid-modified graphene (denoted as GIL) as fillers, were fabricated using solution-cast method and their dielectric properties were carefully characterized. The Raman spectroscopy showed that the ionic liquid and the graphene exhibit the physical cation-π interaction. Ionic liquid can improve the dispersibility of graphene in PVDF matrix by morphology characterization. The percolation thresholds were determined to be 1.86 vol % for PVDF/GIL composites and 0.67 vol % for PVDF/Graphene composites, respectively. Compared with PVDF/Graphene composites, the PVDF/GIL composites exhibited higher dielectric permittivity that originates from the polar β crystals of PVDF and a remarkable Maxwell–Wagner–Sillars (MWS) effect between PVDF and GIL, and the nonconducting organic segments of the ionic liquid can support the low loss tangent and low conductivity in the PVDF/GIL composites. [ABSTRACT FROM AUTHOR]

Biocatalysis has found enormous applications in sorts of fields as an alternative to chemical catalysis. In the pursue of green and sustainable chemistry, ionic liquids (ILs) have been considered as promising reaction media for biocatalysis, owing to their unique characteristics, such as nonvolatility, inflammability and tunable properties as regards polarity and water miscibility behavior, compared to organic solvents. In recent years, great developments have been achieved in respects to biocatalysis in ILs, especially for preparing various chemicals. This review tends to give illustrative examples with a focus on representative chemicals production by biocatalyst in ILs and elucidate the possible mechanism in such systems. It also discusses how to regulate the catalytic efficiency from several aspects and finally provides an outlook on the opportunities to broaden biocatalysis in ILs. [ABSTRACT FROM AUTHOR]

Synergistically improved mechanical and dielectric properties of poly(lactic acid)/ethylene–methyl acrylate–glycidyl methacrylate random terpolymer (PLA/EMA-GMA) based nanocomposites containing ionic liquids (ILs) and multi-walled carbon nanotubes (MWCNTs) can be related to the morphological evolution and interface properties of the composites. ILs can catalyze the reaction between PLA and EMA-GMA and MWCNTs can induce morphology transformation from sea-island structure to quasi-cocontinuous structure. The rheological tests show that the G′ of samples significantly increased and G″ decreased with increasing the MWCNTs content. This indicates that a crosslink structure at PLA/EMA-GMA interface and a solid network structure of EMA-GMA/MWCNTs with quasi-cocontinuous morphology were formed by incorporation of ILs. Morphology transformation and interfacial enhanced compatibilization significantly improved the mechanical and dielectric properties of composites owing to the formation of MWCNTs network in EMA-GMA phase and interfacial crosslinked structure. Image 1 [ABSTRACT FROM AUTHOR]