Ionic liquids

 Ionic liquids

A new research topic that has been installed recently is the use of ionic liquids in the functionalisation of surfaces. As a rule ionic liquid are organic salts that are liquid at temperatures lower than 100 °C. On the one hand these liquids “only” increase the number of solvents available for a lot of applications and processes. Additionally ionic liquids offer certain advantages compared to “non-ionic liquids”. The vapour pressure of ionic liquids is basically zero, which means syntheses or processes utilising such solvents can be carried out without loss of solvent, without reflux equipment or without the need of pressure vessels respectively. Ionic liquids are organic solvents that can be used at high temperatures without the need of explosion protection. Furthermore ionic liquids are known to be extremely temperature stable organic materials – several of them can be employed at temperature higher than 300 °C without decomposition worth mentioned.

Besides these advantageous properties very interesting for a lot of processes a number of ionic liquids are identified that can be used to dissolve compounds or materials that cannot be dissolved in other solvents (or dissolving in other solvents is difficult). To give an example, ionic liquids are known that dissolve up to 30% of cellulose, others that dissolve certain polyurethanes without any problem.

It can be summarized that the use of ionic liquids offers interesting approaches, not at least for modifying surfaces. We proved, in first experiments, that it is possible to modify (“coat”) polyester fibres with cellulose by employing ionic solutions of cellulose with certain additives – such fibres could e.g. be dyed as cotton, appear as a natural fibre and show simultaneously mechanical properties of a synthetic fibre.