In contrast to a recently expressed, and widely cited, view that “Ionic liquids are starting to leave academic labs and find their way into a wide variety of industrial applications”, we demonstrate in this critical review that there have been parallel and collaborative exchanges between academic research and industrial developments since the materials were first reported in 1914 (148 references)

Applications of ionic liquids in the chemical industry

Dissolution of cellulose with ionic liquids and its application : a mini-review

This review gives a survey on the latest most representative developments and progress concerning ionic liquids, from their fundamental properties to their applications in catalytic processes. It also highlights their emerging use for biomass treatment and transformation.

Ionic liquids and catalysis: Recent progress from knowledge to applications

Sustainability, industrial ecology, eco-efficiency, and green chemistry are directing the development of the next generation of materials, products, and processes. Biodegradable plastics and biocompatible composites generated from renewable biomass feedstock are regarded as promising materials that could replace synthetic polymers and reduce global dependence on fossil fuel sources.1 It is estimated that the world is currently consuming petroleum at a rate 100 000 times faster than nature can replace it.2 The growing global environmental awareness and societal concern, high rate of depletion of petroleum resources, concepts of sustainability, and new environmental regulations have triggered the search for new products and processes that are more compatible with the environment. The most abundant natural polymer in our environment is cellulose. It has an estimated annual biosphere production of 90 × 109 metric tons and, consequently, represents the most obvious renewable resource for producing biocomposites.3 Its highly ordered structure is responsible for its desirable mechanical properties but makes it a challenge to find suitable solvents for its dissolution.4 The first attempts to dissolve cellulose date back to the early 1920s.5 Several aqueous and nonaqueous cellulose solvents have been discovered since then, but all of these solvents suffer either from high environmental toxicity or from insufficient solvation power.6 In general, the traditional cellulose dissolution processes require relatively harsh conditions and the use of expensive and uncommon solvents, which usually cannot be recovered after the process.6-10 However, a new class of solvents was opened to the cellulose research community, when in 2002 Swatloski et al. reported the use of an ionic liquid as solvent for cellulose both for the regeneration of cellulose and for the chemical modification of the polysaccharide.7 In 1934, Graenacher had discovered a solvent system with the ability to dissolve cellulose, but this was thought to be of little practical value at the time.11,12 Ionic liquids are a group of salts that exist as liquids at relatively low temperatures (<100 °C). They have many attractive properties, including chemical and thermal stability, nonflammability, and immeasurably low vapor pressure.12 First discovered in 1914 by Walden, their huge potential in industry and research was only realized within the last few decades.13,14 This review aims to provide a summary of our current state of knowledge on the structural features of wood * To whom correspondence should be addressed. E-mail: ken.marsh@ canterbury.ac.nz. Tel.: +64 3364 2140. Fax: +64 3364 2063. † Department of Chemical and Process Engineering. ‡ Department of Mechanical Engineering. Andre Pinkert was born in Schwabach, Germany, in 1981. He studied Chemistry at the University of Erlangen-Nurnberg, Germany, and received his prediploma and diploma degrees in 2004 and 2008, respectively. During 2005, he joined the Marine Natural Products Group, lead by Murray H. Munro and John W. Blunt, at the University of Canterbury (UoC), New Zealand, working on the isolation and characterization of bioactive metabolites. In early 2006, he returned to Germany and resumed his studies at the University of Erlangen-Nurnberg, finishing his degree under the supervision of Rudi van Eldik. Associated with his studies, during 2007, he worked for AREVA NP on radio-nuclear chemistry and computer modeling. Since 2008, he is studying towards a Ph.D. degree at UoC under the supervision of Shusheng Pang, Ken Marsh, and Mark Staiger. His research focuses on biocomposites from natural fibers, processed via ionic liquids. Chem. Rev. 2009, 109, 6712–6728 6712

Ionic Liquids and Their Interaction with Cellulose

Utilization of natural polymers has attracted increasing attention because of the consumption and over-exploitation of non-renewable resources, such as coal and oil. The development of green processing of cellulose, the most abundant biorenewable material on Earth, is urgent from the viewpoints of both sustainability and environmental protection. The discovery of the dissolution of cellulose in ionic liquids (ILs, salts which melt below 100 °C) provides new opportunities for the processing of this biopolymer, however, many fundamental and practical questions need to be answered in order to determine if this will ultimately be a green or sustainable strategy. In this critical review, the open fundamental questions regarding the interactions of cellulose with both the IL cations and anions in the dissolution process are discussed. Investigations have shown that the interactions between the anion and cellulose play an important role in the solvation of cellulose, however, opinions on the role of the cation are conflicting. Some researchers have concluded that the cations are hydrogen bonding to this biopolymer, while others suggest they are not. Our review of the available data has led us to urge the use of more chemical units of solubility, such as ‘g cellulose per mole of IL’ or ‘mol IL per mol hydroxyl in cellulose’ to provide more consistency in data reporting and more insight into the dissolution mechanism. This review will also assess the greenness and sustainability of IL processing of biomass, where it would seem that the choices of cation and anion are critical not only to the science of the dissolution, but to the ultimate ‘greenness’ of any process (142 references).

Ionic liquid processing of cellulose

A modular, ionic liquid (IL)-based strategy allows compartmentalized molecular level design of a wide range of new materials with tunable biological, as well as the well known physical and chemical, properties of ILs, which thus deserve consideration as ‘tunable’ active pharmaceutical ingredients (APIs) with novel performance enhancement and delivery options. IL strategies can take advantage of the dual nature (discrete ions) of ILs to realize enhancements which may include controlled solubility (e.g., both hydrophilic and hydrophobic ILs are possible), bioavailability or bioactivity, stability, elimination of polymorphism, new delivery options (e.g., slow release or the IL-API as ‘solvent’), or even customized pharmaceutical cocktails. Here we exemplify this approach with, among others, lidocaine docusate (LD), a hydrophobic room temperature IL which, when compared to lidocaine hydrochloride, exhibits modified solubility, increased thermal stability, and a significant enhancement in the efficacy of topical analgesia in two different models of mouse antinociception. Studies of the suppression of nerve growth factor mediated neuronal differentiation in rat pheochromocytoma (PC12) cells suggests potential differences between LD and lidocaine hydrochloride at the cellular level indicating an entirely different mechanism of action. Taken together these results suggest that the unique physiochemical properties of ILs in general, may confer a novel effect for the bioactivity of an API due to (at least) slow-release properties in addition to novel delivery mechanisms.

The third evolution of ionic liquids: active pharmaceutical ingredients

Ionic liquid-reconstituted cellulose composites as solid support matrices for biocatalyst immobilization

A dry-jet wet spinning process for making magnetically active cellulose fibers has been developed using the ionic liquid (IL) 1-ethyl-3-methylimidazolium chloride ([C2mim]Cl). Cellulose from different sources with various degrees of polymerization (DP) was used for making fibers by first dissolving the cellulose in the IL, dispersing particles of magnetite in the solution, and then coagulating the fibers in a water bath under appropriate spinning conditions. The variation of fiber properties with cellulose source and concentration of magnetite is discussed. Fiber texture was found to be related to overall magnetite concentration, cellulose concentration, and molecular weight in the spinning solution. In general, it was found that increasing DP and/or cellulose concentration resulted in more robust fibers, and conversely the addition of magnetite particles weakened the overall mechanical properties.

Magnetite-embedded cellulose fibers prepared from ionic liquid

The present invention relates to processes utilizing ionic liquids for the dissolution of various polymers and/or copolymers, the formation of resins and blends, and the reconstitution of polymer and/or copolymer solutions, and the dissolution and blending of 'functional additives' and/or various polymers and/or copolymers to form advanced composite materials.

Daniel T. Daly

Papers

The third evolution of ionic liquids: active pharmaceutical ingredients

Ionic liquid-reconstituted cellulose composites as solid support matrices for biocatalyst immobilization

Magnetite-embedded cellulose fibers prepared from ionic liquid

Polymer dissolution and blend formation in ionic liquids

Ionic liquid-based preparation of cellulose-dendrimer films as solid supports for enzyme immobilization.