Cellulose nanocrystal (CNC) is biodegradable and nontoxic, exhibits many unique chemical, optical, electrical, and piezoelectric properties, which provides the ample opportunity for the development of green and high-performance functional materials for different applications. The key to fully utilize these unique properties of CNC is to obtain CNC film with desirable orientation. It is well known that CNCs can form a chiral nematic structure that can be used to obtain a highly aligned and transparent CNC film. Due to its anisotropic shape, CNCs can be oriented via using mechanical shearing. It is expected that the higher the shear rate, the higher the orientation degree of CNC. Unfortunately, a higher shear speed can result in cracking and localized defect in CNC films, which would affect the functionalities of the CNC film, lowering the stability, mechanical strength, and piezoelectric coefficient of CNC film. Additionally, it is important to notice that CNC film is brittle, which limit their applications.<br/>The aim of this research is to develop a CNC-based films with a high orientation but being flexible so that these films can be used as a coating or piezoelectric material without the limitations mentioned above. It is experimentally found that adding electrolytes can significantly enhance the orientation degree of CNCs in film i.e., from 32% (without electrolyte) to 90% (with electrolyte) for a constant shear rate of 955 s<sup>-1</sup>. Moreover, it is experimentally observed that CNC film with electrolyte is flexible. The detailed experimental conditions and relationship between the experimental conditions (i.e., content of electrolyte, shear rate, thickness) and the (mechanical, optical, rheological, barrier, and piezoelectric) properties of CNC films are summarized with speculations on the mechanism. The structure, microstructure and morphology of the CNC films are characterized and used to deepen the understanding of observed properties in these CNC films.

Tune CNC alignment by combining the additions of electrolytes with shear based alignment

ACS Spring 2022

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