Understanding the effect of ionic liquids on the foaming ability of a natural based polymer

The work presented hereafter is part of a larger project which intends explore novel processing routes for the processing of natural-based polymers, joining together processes, materials and chemicals, maximizing the use of “greener” processing routes, environmental safer solvents and reagents and raw materials from renewable sources, and minimizing energy and industrial time. Processing natural-based polymers still remains a challenge due to their low solubility in water and in most organic solvents. In order to overcome this, ionic liquids (ILs) have received great attention in recent years as green solvents for natural based polymer, such as cellulose, chitin and starch, among others.The interesting properties that ILs present (viscosity, density, hydrophilicity, solubility) make them useful for diverse applications  and the possibility of coupling ILs with supercritical fluid technology has lead to major breakthrough developments. Supercritical fluid foaming has proven to be a promising alternative to prepare structures with enhanced porosity. In a previous work we evaluated the effect of ionic liquids on the foaming behavior of a starch-poly-ε-caprolactone blend (SPCL) ]. The supercritical fluid foaming technique is limited to semi-crystalline or amorphous polymers in which carbon dioxide can be dissolved. The principle of the process is the decrease in the polymer glass transition temperature which, upon depressurization leads to cell nucleation and growth and pore formation . Ionic liquids have been reported as plasticizers for natural-based polymers, enhancing the supercritical fluid foaming process . In this work we will provide more insights on the mechanisms underlying this process, doping SPCL with different ionic liquids and different concentrations. Different characterization techniques were employed to study the effect of IL on the polymers.