We report the enthalpies of vaporisation (measured using temperature programmed desorption by mass spectrometry) of twelve ionic liquids (ILs), covering four imidazolium, [C(m)C(n)Im]+, five pyrrolidinium, [C(n)C(m)Pyrr]+, two pyridinium, [C(n)Py]+, and a dication, [C3(C1Im)2]2+ based IL. These cations were paired with a range of anions: [BF4]-, [FeCl4]-, [N(CN)2]-, [PF3(C2F5)3]- ([FAP]-), [(CF3SO2)2N]- ([Tf2N]-) and [SCN]-. Using these results, plus those for a further eight imidazolium based ILs published earlier (which include the anions [CF3SO3]- ([TfO]-), [PF6]- and [EtSO4]-), we show that the enthalpies of vaporisation can be decomposed into three components. The first component is the Coulombic interaction between the ions, DeltaU(Cou,R), which is a function of the IL molar volume, V(m), and a parameter R(r) which quantifies the relative change in anion-cation distance on evaporation from the liquid phase to the ion pair in the gas phase. The second and third components are the van der Waals contributions from the anion, DeltaH(vdw,A), and the cation, DeltaH(vdw,C). We derive a universal value for R(r), and individual values of DeltaH(vdw,A) and DeltaH(vdw,C) for each of the anions and cations considered in this study. Given the molar volume, it is possible to estimate the enthalpies of vaporisation of ILs composed of any combination of the ions considered here; values for fourteen ILs which have not yet been studied experimentally are given.

Highest heat of vaporization yet: The dicationic ionic liquid [C(3)(C(1)Im)(2)][Tf(2)N](2) evaporates as a neutral ion triplet. These neutral ion triplets can then be ionised to form singly and doubly charged ions. The mass spectrum exhibits the dication attached to one remaining anion, and the naked dication itself (see picture).

The free-radical polymerization of methyl methacrylate (MMA) in ionic liquids at low monomer concentration is reported with emphasis on elucidating the “magic” rate and molecular weight enhancement that are often observed. We show that traditional methods of molecular weight capping using dodecylmercaptan as chain transfer agent significantly reduces the molecular weight of the polymer, but to a much lesser extent than analogous reactions in xylene. Similarly, the adverse effect of elevated temperatures upon reactions of this type is much less significant for polymerizations conducted in ionic liquids than those in organic solvents. Indeed, almost quantitative yield can be obtained for polymerization at temperatures up to 120 °C in ionic liquid, while almost no polymer is observed in an organic solvent case due to rapid initiator burnout. These factors lead to the proposal that a “protected” radical mechanism is in operation; however, elucidation of the exact nature of this protection remains elusive. As an extension of this hypothesis, block copolymers of methyl methacrylate, grown from styrene, have been prepared and characterized by NMR, GPC-MALLS, GPEC, and DSC. The absence of poly(methyl methacrylate) homopolymer in the final product suggests that the monomer is only initiated from “protected” polystyrene macroradicals in the ionic liquid. This process cannot be reproduced in organic solvents, unless additional control agents are present. Furthermore, we report much higher molecular weights of A−B block copolymers than those previously reported in the literature.

The development of high-yielding, "greener" chemistry-based routes for the continuous synthesis of methyl ethers are reported in this study. Ethers have been efficiently produced using a methodology which eliminates the use of toxic alkylating agents and reduces the waste generation that is characteristic of traditional etherification processes. For the first time it is shown that the use of acidic heterogeneous catalysts can successfully achieve etherification when using scCO 2 as a reaction medium. Furthermore, the relative efficiencies of three alternative methylating agents, dimethyl carbonate, dimethyl ether and MeOH, have been compared and contrasted for the methylation of 1-octanol. Dimethyl carbonate has proven to be the superior methylating agent, demonstrating higher conversion and selectivity. Successful methylation of secondary alcohols, diols, carboxylic acids and amines using dimethyl carbonate in supercritical carbon dioxide has also been shown. Substrate structure was found to influence the temperature required to maximize the yield of the desired product, substrates with multiple hydroxyl groups requiring the highest temperatures.