A New Proposal of Preparation of Different Polymorphs of Nanocellulose from Eucalyptus citriodora

Cellulose is a renewable, sustainable, and high available biopolymer; their common form is the type-I polymorph. However, polymorphic changes are associated with different properties and a wide range of applications. In this study, we proposed a new method to prepare polymorphic cellulose nanostructures (CNSs): first, the CNS were isolated, and then the polymorphs were converted. CNS-I (type-I), CNS-II (type-II), and CNS-III (type-III) were successfully obtained, and the structure, crystallinity, superficial characteristic, morphology, and thermal stability were evaluated. The results showed that CNS-II and CNS-III are more amorphous than CNS-I due to the strong reagents used for the polymorphic conversion, which results in a swelling, increased chain spacing, and structural disorganization. This effectively changed the morphology of the CNS, from cellulose nanocrystals from irregular quasi-spherical nanoparticles. The proposed method allows a wide range of applications, from package and nanocomposites with CNS-I due to its high crystallinity and crystal morphology, to drug carrier, food thickener and biomedical products for CNS-II and CNS-III due to its quasi-spherical shape and more amorphous structure. Graphic Abstract