(634d) Tune Cellulose Nanocrystal Alignment By Combining the Additions of Electrolytes with Shear-Based Alignment

Cellulose nanocrystal (CNC) is a renewable, non-toxic and biodegradable material. It is produced from inexpensive renewable biomass and exhibits several unique chemical, optical, electrical, and electromechanical properties. To fully utilize these unique properties, CNCs have to be aligned with a high degree. However, the self-assembled CNC film exhibits low transparency due to its chiral nematic structure. When a simple mechanical shearing is applied, CNCs can be aligned so that CNC films are transparent with an enhanced chemical barrier property. It is also expected that CNC film with a high orientation degree exhibits a piezoelectric effect. A higher shear rate can result in a higher degree of alignment. However, CNC film made using a higher shear rate include more cracking and localized defect. Additionally, very higher alignment is not easy to achieve by a single mechanical shear stroke when dealing with CNC gel.

The aim of this project is to develop a CNC-based material from CNC gel which can be used as a coating or piezoelectric material without the limitations mentioned above. With the addition of electrolytes, the alignment degree of CNC can be significantly enhanced. For example, for a shear rate of 1,000 s^-1, the alignment degree increases from 32% without electrolyte to 90% with electrolyte. In addition, it is observed that adding electrolyte also significantly improve the flexibility of CNC films. This study also provides insights into the effect of the experimental conditions (i.e., the type of electrolytes, shear rate, and thickness) on the mechanical, optical, rheological, barrier, and piezoelectric properties of CNC films.