Cellulose regeneration in ionic liquids: factors controlling the degree of polymerisation

The degree of polymerisation (DP), is an important polymer property which has a direct influence on the mechanical properties such as tensile strength. Here we measure the degree of polymerisation of regenerated cellulose dissolved in the ionic liquids 1-butyl-3-methylimidazolium acetate (BMIMOAc) and 1-allyl-3-methylimidazolium chloride (AMIMCl), at different dissolution temperatures, times and coagulants. We show that dissolution temperature has a dramatic impact on the DP of the regenerated cellulose. The DP of cellulose dissolved at 130 °C was measured at 230 while the DP of cellulose dissolved at 80 °C was measured at 650. We also show that ionic liquid remains trapped in the regenerated cellulose and over a period of 2 years a significant reduction in DP was measured. This is likely due to the continued interaction between the cellulose and the trapped ionic liquid.