Influence of Anomeric Configuration on Mechanochemical Degradation of Polysaccharides: Cellulose versus Amylose

Abstract

Cellulose and amylose are (1-->4)-linked polysaccharides that are used extensively in the textiles, paper, and food and feed industries and are finding increasing use as alternative fuels and so forth. At the molecular level, cellulose and amylose differ only in their anomeric configuration: beta in cellulose, alpha in amylose. During processing and end use, these polymers experience a variety of mechanochemical stresses, many through contact with transient elongational flow fields. Here, we subject solutions of both polysaccharides to extended periods of ultrasonic irradiation, as the cavitational bubble collapse characteristic of ultrasound experiments creates flow fields strictly analogous to those encountered in other transient elongational flow scenarios. With the use of multidetector size-exclusion chromatography, the effects of anomeric configuration on both the limiting molar mass, beyond which polymers do not degrade in transient elongation flow ( M lim), and the rate of degradation have been isolated in these (1-->4)-linked polysaccharides. This effect was found to be pronounced; for example, M lim (cellulose) = 5( M lim (amylose)). Also, while extensive change was observed in molar mass averages, distribution, polydispersity, and size of the analytes during degradation, their structure was found to remain invariant. A modified "path theory" of transient elongational flow degradation was proposed, with the persistence length identified as a parameter which embodies the minimum continuous path length and flexibility requirements of the theory.