Irreversible transformations of native celluloses, upon exposure to elevated temperatures.

Current research, basic and applied, assumes that observed recalcitrance of celluloses is an inherent characteristic associated with their state of aggregation in their native state; it is thought that processes of isolation remove other components of plant cell walls leaving the celluloses unchanged, even though elevated temperatures are routinely used during isolation. Since temperature elevation is known to influence the structures of all polymers, it is important to explore its influence on the character of isolated celluloses, almost always assumed to be still in their native state. Deuterium exchange is a measure of accessibility of reactive sites in celluloses. We report significant reduction in accessibility to deuterium and other probe molecules for celluloses isolated at ambient temperature and then exposed to elevated temperatures. Our results indicate that native celluloses, which are highly ordered biological structures, are irreversibly transformed and develop polymeric semi-crystalline character upon isolation at elevated temperatures.