Certain concentrated mixtures of salts and solvents are not simply “solutions” anymore, but they may be described as “ionic liquids”. In this perspective paper, we describe possible criteria for the new family of ionic liquids: “solvate” ionic liquids. This subclass of ionic liquids was originally proposed by Angell et al. in their recent review; however, their criteria remain to be debated. Concentrated mixtures of lithium salts and organic solvents are useful models for these solvate ionic liquids, and the effects of the salt concentration, types of solvents, and counter anions of the lithium salts on their structure and properties have been explored to enable contrast with traditional solutions, and to help determine whether a given mixture belongs to the solvate ionic liquid or not.

https://www.rsc.org/suppdata/cp/c4/c4cp00461b/c4cp00461b1.pdf

Criteria for solvate ionic liquids

A vibrational analysis has been carried out to analyze the chain conformation of poly(lactic acid) in the crystalline state. In conjunction with a normal-coordinate analysis, the Raman spectrum has yielded data regarding conformational distributions. Raman spectra of different helices were simulated using previously published structures, force constants, and intensity parameters. Some of the chain conformations predicted are inconsistent with the data. Only one of the four 31 helical structures predicted by conformational analysis agrees well with experiment. This analysis provides a new understanding regarding the relative probability of a 103 or 31 helix for poly(lactic acid).

A Spectroscopic Analysis of Poly(lactic acid) Structure

Precise synthesis and surface structures of architectural per- and semifluorinated polymers with well-defined structures

An equimolar mixture of lithium bis(trifluoromethanesulfonyl)amide (Li[TFSA]) and either triglyme (G3) or tetraglyme (G4) yielded stable molten complexes: [Li(G3)][TFSA] and [Li(G4)][TFSA]. These are known as solvate ionic liquids (SILs). Glyme-based SILs have thermal and electrochemical properties favorable for use as lithium-conducting electrolytes in lithium batteries. However, their intrinsically high viscosities and low ionic conductivities prevent practical application. Therefore, we diluted SILs with molecular solvents in order to enhance their ionic conductivities. To determine the stabilities of the complex cations in diluted SILs, their conductivity and viscosity, the self-diffusion coefficients, and Raman spectra were measured. [Li(G3)]+ and [Li(G4)]+ were stable in nonpolar solvents, that is, toluene, diethyl carbonate, and a hydrofluoroether (HFE); however, ligand exchange took place between glyme and solvent when polar solvents, that is, water and propylene carbonate, were used. In acetonitr...

Li+ Solvation and Ionic Transport in Lithium Solvate Ionic Liquids Diluted by Molecular Solvents

The polymer chain conformation under confinement and the morphology of the nanohybrid materials are investigated in hydrophilic polymer/layered silicate nanocomposites. A series of poly(ethylene oxide)/sodium montmorillonite hybrids were synthesized utilizing melt intercalation with compositions covering the complete range from pure polymer to pure clay. Intercalated nanocomposites with mono- and bilayers of PEO chains are obtained in all cases. The intercalated chains as well as the ones adsorbed on the outer surface of the clay particles remain purely amorphous; their conformation, however, exhibits different characteristics from those of the amorphous neat polymer melt. It is only for compositions where a large amount of excess polymer exists outside the completely full galleries that the polymer crystallinity is recovered.

Crystallinity and Chain Conformation in PEO/Layered Silicate Nanocomposites

Isotropic Raman spectra of poly(ethylene oxide) in aqueous solution and in the melt show differences in the skeletal stretching vibration bands near 800 cm-1 and in the disordered longitudinal acoustic mode feature in the 200−400 cm-1 region. These spectra may be simulated by superposing calculated spectra resulting from a series of normal coordinate calculations performed for an ensemble of conformers. The conformational distribution for poly(ethylene oxide) in the molten state appears to favor the tgg‘ conformer, which dominates the spectrum calculated to match closely the observed isotropic Raman spectrum. It appears that the experimental data suggest that the tgg‘ conformation is present by a greater amount than is predicted by previous simulation methods. On the same basis, it appears that the aqueous solution of poly(ethylene oxide) contains mostly tgt conformers. The results for poly(ethylene oxide) were supported by measurements and computations made using 1,2-dimethoxyethane as a model.

Raman Analysis of a Conformational Distribution of Poly(ethylene oxide) and Its Model Compound in the Liquid State

Samples with one or both ends of monodisperse poly(ethylene oxide) (PEO) functionalized with perfluorodecanoyl groups (PEOF or PEO2F) were synthesized and blends of these end-capped PEOs with PEOs of the same molecular weight (Mn ∼2000 to ∼16 000 K) were prepared as cast films. As-cast and annealed samples were analyzed by X-ray photoelectron spectroscopy (XPS) and contact angle analysis. XPS analysis was also performed on samples at elevated temperatures (melts). Due to the lower surface energy of the fluorocarbon end groups, the modified PEOs preferentially adsorb to the free polymer surface. The surface concentration of the perfluoroalkyl end groups was measured by XPS which indicates that perfluoroalkyl chain ends adsorb to the polymer surface in a reasonably close-packed fashion (at all molecular weights) and leave a zone depleted of fluorine immediately beneath the highly fluorinated surface region. The dependence of adsorption on temperature was investigated for one sample and adsorption appears to...

Adsorption of end-functionalized poly(ethylene oxide)s to the poly(ethylene oxide)-air interface

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Raman Analysis of a Conformational Distribution of Poly(ethylene oxide) and Its Model Compound in the Liquid State

Adsorption of end-functionalized poly(ethylene oxide)s to the poly(ethylene oxide)-air interface