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To investigate the performance of graphene (Gra) modified with ethoxycarbonyl ionic liquid (IL), chain mobility and crystallization kinetics of poly(L-lactic acid) (PLLA), a series of PLLA nanocomposites have been prepared using solution-cast method. IL can improve the dispersion of Gra in PLLA matrix and the samples containing IL have higher growth rate of PLLA spherulite than neat PLLA does. PLLA/IL/Gra and PLLA/2Gra exhibit the same relaxation strength and time of αN relaxation that corresponds to the longest normal mode motion at 110−140 °C. PLLA/IL/Gra shows a faster crystallization rate than PLLA/2Gra does, which might be attributed to the Gra-imidazolium cation interaction in IL modified Gra, the significant dispersion effect of IL at Gra surface, and the increase of nuclei density of PLLA/IL/Gra. [ABSTRACT FROM AUTHOR]

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]

To investigate the effect of graphene oxide (GO) modified by polymerized ionic liquid (PIL) on the crystallization and dielectric relaxation of poly(vinylidene fluoride) (PVDF), a series of PVDF composites have been prepared using the solution casting method. The ion-dipole interaction between PIL and >CF2 and the π-dipole interaction between GO and >CF2 can induce synergistically the polar phase, and the π-ion interaction between GO and PIL can strengthen the induction effect of the polar phase and decrease the degree of crystallization of PVDF. The electric modulus and conductivity relaxation are employed to analyze the experimental complex dielectric permittivity. In the frequency spectra of complex permittivity of PVDF composites, space charge polarization and conductivity lead to a large value of dielectric permittivity. The temperature dependence of relaxation time of conductivity relaxation accords with the Arrhenius equation. A low degree of crystallization, more ion concentration, and polar phase in PVDF/PIL/GO enhance the movement of the polymer chain segment and charge carriers. [ABSTRACT FROM AUTHOR]

The effect of 1,2,3-triazolium-functionalized PCL-b-PEG block copolymer (PCL-b-PEG(IL)) on crystallization behavior and kinetics of PLA was systematically studied by DSC, POM and XRD. A small amount of micelle of aggregated PCL-b-PEG(IL) containing ionic clusters and a large number of disaggregated PCL-b-PEG(IL) can significantly improve the chain segment mobility of PLA. The glass transition temperature and cold crystallization temperature of PLA gradually decreased with the increase in PCL-b-PEG(IL) or PCL-b-PEG content. Compared with PCL-b-PEG, PCL-b-PEG(IL) decreases the Tg of PLA more obviously because of the strong plasticizing effect of PCL-b-PEG(IL). More importantly, the isothermal crystallization kinetics results manifested that the synergistic effect of heterogeneous nucleation agent of ionic clusters of PCL-b-PEG(IL) and chain mobility promoter of PEG chain segment can enhance the crystallization ability of PLA at all crystallization temperature. The 5 mass% PCL-b-PEG(IL) can induce high amount of stable α-form crystal of PLA after annealing treatment. [ABSTRACT FROM AUTHOR]

A tri-arm star-shaped oligomer with PEG arm and imidazolium-based ionic liquid moiety (TSIL) was introduced in poly(lactic acid) (PLA) blends, and the synergetic effects of PEG arm and IL moiety contained in the TSIL on the crystallization behaviors of PLA were investigated by DSC and POM. The results determined by DSC show that TSIL inhibits the crystallization of PLA when the mass content of TSIL in blend is as low as 1 mass%, while the crystallization process is accelerated greatly with increasing mass content of TSIL. As revealed by POM observations, the spherulitic morphology remains unchanged in TSIL/PLA blends and the nucleation and growth of spherulites are altered due to the different effects of PEG arm and IL moiety. The nucleation process is suppressed by IL moiety, while the growth rate of spherulites is improved because of the plasticizing effect of PEG arm. The synergistic effects of PEG arm and IL moiety contained in the TSIL also contribute to the acceleration of kinetics in non-isothermal crystallization process. [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]