The 4th International Congress on Ionic Liquids (COIL-4) was held in Washington, DC June 15-18, 2011 to explore the fascinating world of the science and application of ionic liquids.  This meeting was the 4th in a series of successful meetings dating back to June 2005 when over 450 participants from 33 countries met in Salzburg, Austria to discuss and debate the lively topic of ionic liquids.  Equally successful meetings were subsequently held in Yokohama (COIL-2, 2007), and Cairns, Australia (COIL-3, 2009).


Ionic Liquids are not new materials ‑ they have been known for over 100 years, but have gained a substantial growth in renewed interest over the last 20 years, and particularly from 1995 onwards, first due to efforts by the United States Air Force in applying ILs as electrolytes, and then as a result of suggestions that ILs have unique properties as VOC solvent replacements and materials with new combinations of physical properties.  Today ILs are defined generally as those salts with melting points below 100 °C and whose melts are composed of discrete ions, but it is often the unique materials properties set, unavailable from molecular compounds or crystalline salts, that are bringing ILs under even more intense scrutiny.


The intrinsic non‑volatility, thermal stability, and large liquidus ranges achievable with many ILs have proven to be important drivers for research, supporting numerous advances beyond the initial investigations of ILs as liquid electrolytes.  Current topics include electrochemistry, separation science, chemical synthesis, catalysis, pharmaceuticals, and many others. Furthermore, the growing social pressure for new green technologies, and the promise of ILs to deliver such, has led to high academic and industrial interest in IL technologies.  This interest in ILs and their applications has led synergistically to the development of an extensive and diverse range of salts that can support low-melting IL phases (with component ions ranging from simple, mononuclear, to complex), and to the exploration of materials applications utilizing the novel characteristics of these IL phases. These include thermal fluids, lubricants, processing of biomass, biphasic chemical processes, photovoltaics, fuel cell electrolytes, and energetic liquids.


COIL-4 marked the first opportunity for the United States to host this meeting and it came at an auspicious time.  Interest in ionic liquids was and is rapidly growing in the US, in part because of the fascinating set of physical, chemical, and biological property sets these materials possess, and in part from the growing realization of new applications in such key areas as Sustainable Energy, Biomass, Biorefineries, Renewable Fuels and Chemicals, Materials, Pharmaceuticals, Separations, Catalysis, and Biotechnology (to name a few).  Government and industrial funding in the area were rapidly increasing.


COIL-4 also occured at a time when misconceptions about ionic liquids threatened to overshadow the high level of science that has led to new fundamental insight and a large number of new applications.  Overstatements which try to define ionic liquids as ‘green,’ detract from the strategies being employed around the world to use the unique properties of ionic liquids to develop sustainable products and processes. Ionic liquids can clearly be designed to be flammable, unstable, or even toxic (properties which have also led to interesting applications).  They can also be designed to be nonflammable, stable, and nontoxic, and it is this design choice which has intrigued many scientists and engineers.


COIL-4 represented an opportunity to meet and discuss these and other major topics in the field with international experts.  In addition, representatives from large and small industry provided insight into key issues such as scale-up, costs, availability, registration, and other key parameters needed to plan new ventures.


The Scientific program included 8 Plenary Lectures (45 minutes), 35 Keynote and Featured Lectures (30 minutes), and a number of contributed talks (20 minutes).  Lively poster sessions and social events provided much time for interaction with ionic liquid scientists and engineers from around the world. 


We are all looking forward to COIL-5 to be held in Portugal in 2013!