Magnetic Fluids Based on gamma-Fe(2)O(3) and CoFe(2)O(4) Nanoparticles Dispersed in Ionic Liquids

The disclosure of magnetic ionic liquids (MILs) as stable dispersions of surface modified gamma-Fe(2)O(3) or CoFe(2)O(4) nanoparticles (NPs) in the 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMIBF(4)) ionic liquid is reported. The magnetic NPs were characterized by X-ray powder diffraction, transmission electron microscopy, and Raman spectroscopy. The surface modified NPs have proved to form stable dispersions in BMIBF(4) in the absence of water and behave like a magnetic ionic liquid. The MILs have been characterized by Raman spectroscopy, magnetic measurements, and DSC. The stability of the magnetic NPs in BMIBF(4) is consistently explained by assuming the formation of a semiorganized protective layer composed of supramolecular aggregates in the form of [(BMI)(2)(BF(4))(3)](-). A superparamagnetic behavior and saturation magnetization of ca. 18 emu/g for a sample containing 30% w/w maghemite NPs/BMIBF(4) have been inferred from static and dynamic magnetic measurements. DSC results have shown that the MIL composed of 30% w/w CoFe(2)O(4) NPs/BMIBF(4) remains a liquid phase down to -84 degrees C.

Tunable wettability of polyimide films based on electrostatic self-assembly of ionic liquids

We have demonstrated that the surface wettability of negatively charged polyimide films could be turned by electrostatic self-assembly of ionic liquids. The water contact angles of the polyimide films varied in the range 27-80 degrees for 13 different ionic liquids based on imidazolium and ammonium salts. The surface morphology of the resulting surfaces was characterized using atomic force microscopy. The results revealed that the assembly of longer-substituent cations was characterized by the formation of spherical nanoparticles that were formed due to sequent aggregation of cations on those electrostatically assembled ones via hydrophobic interaction. In this case, the counteranions are present in the assembled layers and the wettability is accordingly affected. Whereas for shorter-substituent cations, no aggregates were formed due to the less hydrophobic interaction than the electrostatic repulsive interaction between the cations, and the counteranions were absent from the assembled layers. This method can also be utilized to quantify the hydrophobicity of various ionic liquids.

Use of ionic liquids as electrolytes in electromechanical actuator systems based on inherently conducting polymers

The use of ionic liquids (ILs) as electrolytes for electromechanical actuators based on polypyrroles (PPy's) is described. The composition of the electrolytes has a significant effect on the electrochemical properties of the PPy actuator and subsequently on actuator performance, improving cycle life and strain generated. The actuator performance in ionic liquid electrolytes is significantly better than that in traditional organic and aqueous electrolytes.

Protic ionic liquids based on the dimeric and oligomeric anions: [(AcO)xHx−1]−

We describe a fluidity and conductivity study as a function of composition in N-methylpyrrolidine–acetic acid mixtures. The simple 1:1 acid–base mixture appears to form an ionic liquid, but its degree of ionicity is quite low and such liquids are better thought of as poorly dissociated mixtures of acid and base. The composition consisting of 3 moles acetic acid and 1 mole N-methylpyrrolidine is shown to form the highest ionicity mixture in this binary due to the presence of oligomeric anionic species [(AcO)_xH_x−1]− stabilised by hydrogen bonds. These oligomeric species, being weaker bases than the acetate anion, shift the proton transfer equilibrium towards formation of ionic species, thus generating a higher degree of ionicity than is present at the 1:1 composition. A Walden plot analysis, thermogravimetric behaviour and proton NMR data, as well as ab initio calculations of the oligomeric species, all support this conclusion.

Low viscosity ionic liquids based on organic salts of the dicyanamide anion

New families of salts viz. quaternary ammonium, N-alkyl-N-methylpyrrolidinium or 1-alkyl-3-methylimidazolium dicyanamides, Cat⁺N(CN)₂⁻, are low melting compounds, most being liquid at rt, water-miscible and have low (for ionic liquids) viscosity at rt, e.g.η = 21 cP for 1-ethyl-3-methylimidazolium dicyanamide.

A new family of ionic liquids based on the 1-alkyl-2-methyl pyrrolinium cation

Five new salts based on 1-alkyl-2-methyl pyrrolinium ion are reported, two involving the iodide ion and three involving the bis(trifluoromethanesulfonyl) amide ion. The iodide salts have melting points around 100 °C, while the amide salts have melting points around room temperature. Two of the amide salts can be easily quenched into the glassy state and exhibit glass transition temperatures around −70 °C. The 2-methyl pyrrolinium cation bears structural similarities to the aromatic imidazolium cations on one hand and the cyclic ammonium cation family based on the pyrrolidinium cation on the other. The properties of the salts reported here are compared within these two related families of salts.

Novel biorenewable plastics based on natural resources using ionic liquids

We report biorenewable plastics developed from natural resources such as cellulose, wool and microorganismsynthesized poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) copolymer [1-3]. Novel materials were prepared by blending these natural polymers in an ionic liquid green solvent, 1-butyl-3-methylimidazolium chloride. Cellulose /PHBV blend materials were successfully prepared in this way. The ionic liquid was completely recycled with high yield and purity after the processing. The blend materials can be processed into different solid forms such as films, noodle-like fibers and bulk blocks. It was found that there exists hydrogen bonding interaction between the components which facilities the mixing of these polymers. The cellulose/PHBV blend materials all show phase-separated structure as revealed by micro ATR-FTIR imaging (Figure 1) and scanning electron microscopy (SEM). The PHBV domains of 6 - 8 µm are distributed in a cellulose matrix at high concentrations of cellulose while the blend materials with high PHBV concentrations exhibit multiphase morphologies, including beadlike PHBV microdomains in the range of 300-400 nm. The dispersion of PHBV in cellulose leads to significant improvement in hydrophobicity due to its beadlike structure. The blend materials represent a class of degradable plastics from natural bioresources using the ionic liquid green solvent.

Protic ionic liquids based on phosphonium cations : comparison with ammonium analogues

Novel protic ionic liquids (PILs) based on a tributyl phosphonium cation have been synthesised and characterised, revealing that the phosphonium based ILs show high thermal stability, high ionic conductivity and facile proton reduction compared to the corresponding ammonium based ILs.

Cellulose-based biodegradable blends and composites regenerated from ionic liquids

This thesis presents the fabrication of biodegradable polymer blends and composites with the assistance of ionic liquids. The work included preparation and characterization of cellulose/PCL blend films, cellulose/ PCL-PDMS-PCL blend films, cellulose/ PVAL blend films and cellulose/clay composite films. An efficient and feasible approach of reducing plastic pollution was developed.