Influence of the molecular weight distribution of cellulose on the rheological properties of cellulose-ionic liquid solutions

Ionic liquids are a novel class of solvents which have attracted a large interest from industrials and researchers side during the last few years. Indeed, their desirable properties such as high thermal stability or non-detectable vapour pressures make Ionic liquids a perfect alternative solvent to organic ones in the concept of green chemistry. Moreover, wood cellulosic fibres for textile application are nowadays in the focus of new interest due to the green aspect of wood as material. However, their manufacturing processes are environmentally questionable. Thus, an alternative process has to be found. The production of wood cellulosic textile fibre by direct dissolution of cellulose in ionic liquids (ILs) and subsequent regeneration combine two major green chemistry principles: using environmentally preferable solvents and bio-renewable feed-stocks. While it has been already proved that some ionic liquids are efficient non-derivatizing solvents for cellulose, only little is known about the rheological behaviour of cellulose-ILs solutions, which is a pre-request for processing and regenerating cellulose in the form of textile fibre. In this study, cellulose blends of different molecular mass distribution were dissolved at commercially relevant concentrations of 10 w/w % in 1-ethyl-3-methylimidazolium acetate (EMIM OAc). The dissolution performed in a vertical kneader at 80°C, showed a limited degradation of the cellulose chains. The extensional rheological properties of cellulose-EMIM OAc solutions measured with a capillary break-up extensional rheometer (CaBER), were compared to classical oscillatory shear rheology in order to study the influence of the molecular mass distribution of cellulose on rheological properties. It was observed that the high molecular weight fractions of cellulose have an impact on the rheological properties of cellulose-EMIM OAc solutions, confirming the previous observation found in the literature