Cellulosic materials show significant promise in many applications where synthetic polymer components are traditionally used. Cello-oligosaccharides are low molar mass polymers of cellulose that show promise as low-concentration additives in biofuels and food products as well as synthetic tools in the health industry . Multiple top-down and bottom-up methods have been investigated to prepare cello-oligosaccharides. Notable among them for its ease-of-use however is hydrolysis of bulk cellulose materials using concentrated phosphoric acid. This method can be used to produce cello-oligosaccharides of controlled length (where longer hydrolysis times lead to smaller polymers) but takes weeks to accomplish. Herein we describe a new method to produce cello-oligosaccharides using phosphoric acid whereby increasing the temperature to 55 °C and mixing mechanically results in cello-oligosaccharides of controlled lengths (degree of polymerization 10-20) in under 9 hours . Gel permeation chromatography (GPC) was used to determine weight average molecular weight (M_w) and degree of polymerization (DP_w) as well as dispersity (D) of these cello-oligosaccharides and methods of GPC were compared to determine their accuracy.

Obtaining reliable values for molar mass of cellulose is difficult in part due to its insolubility in common solvents as well as a general lack of standard operating methods.^[1] As such, we compare the use of (1) GPC of derivatized cellulose (cellulose tricarbanilate) dissolved in DMSO and (2) GPC of cellulose dissolved in DMAc/LiCl (a non-derivatizing solvent approach) to accurately and precisely measure M_w and D of cellulose polymers. In doing so we make recommendations for the most suitable M_w characterization methods for cellulosic materials in addition to suggesting ideal operating parameters and protocols for such measurements.

Cameron King

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