Closing the cellulose 'degree of polymerisation-availability gap': maximising reaction selectivity at high space-time yields by low-cost 'amorphisation'

Despite being the first industrially utilised polymer, the key applicability of cellulose has been limited by its inability to be low-cost melt processed. The clear limiting feature is its crystallinity, which also puts serious kinetic restrictions on heterogeneous chemical processing, due to poor statistical access to the polymer. As such, there exists a 'DP-availability gap', where the lower end is represented by microcrystalline cellulose, which is close to the level-off degree of polymerisation. Herein we describe a scalable method for preparation of low molecular weight celluloses, using an amorphization step, followed by Malaprade oxidation and β-elimination. The amorphisations were performed using low-cost inorganic salt pre-treatments, to increase statistical access to the polymer. Malaprade oxidation was performed to introduce units which were susceptible to β-elimination. This was then enacted using a mild alkaline washing step, producing new reducing ends from the chain-scissions. The efficacy of the pre-treatments was thoroughly characterised showing a clear mechanistic basis for polydispersity control, in addition to control over the molecular weight through oxidation stoichiometry. Overall, this offers a scalable method, for production of technical materials for innovation, where the 'DP-availability gap' can be closed.