Polymorphic and morphological transformations of cellulosic materials are strongly associated to their properties and applications, especially in the case of emerging nanocelluloses. Related changes that take place upon mercerization of individual cellulose nanocrystal (CNC) are studied here by XRD, TEM, AFM, and other techniques. The results indicate polymorphic transformation of CNC proceeds gradually in a certain range of alkali concentrations, i.e. from about 8% to 12.5% NaOH. In such transition alkali concentration, cellulose I and II allomorphs coexist. Such value of the transition concentration is strongly interdependent with CNC crystallinity. In addition, it is distinctively lower than that for macroscopic fibers (12-15% NaOH). Transmission electron microscopy and particle sizing reveals that after mercerization CNC tends to associate. Furthermore, TEMPO-oxidized mercerized CNC reveals the morphology of individual nanocrystal of the cellulose II type, which included some granular structures interconnected by cellulose bridges. Overall, this work reveals how the polymorphism and morphology of individual CNC changes by mercerization and sheds light onto the polymorphic transition from cellulose I to cellulose II.

Polymorphic and morphological changes of cellulose nanocrystals during mercerization

251st National Meeting (2016)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.