Cellulose is one of the most abundant and sustainable natural materials. Cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs), possessing somewhat different morphological parameters, have been widely used for fabricating novel bio-based nanomaterials with unique properties. Although both are nanofibrils, CNCs are stiffer needle-like crystals with a width of 10-20 nm and several hundred nanometers in length. On the other hand, CNFs consist of crystalline and amorphous regions, making them semi-flexible with a width of 2-5 nm and up to 1 µm in length. In dispersion, semi-flexibility of CNFs, concentration and aspect ratio are the major factors controlling the network characteristics (e.g., pore size and crowding factor). By developing the fundamental understanding of network dynamics at the nano scale, it is possible to design advanced functionalized materials. In this context, we have studied the effect of semi-flexibility, concentration and aspect ratio of generalized cellulose nanoparticles on the network dynamics and characteristics with the help of coarse-grained simulations of Brownian dynamics in three dimensions. To have a better understanding of diffusivity in the system, spherical nanoparticles, acting as tracers, have been introduced into the network. The results show that networks made of nanofibrils with higher aspect ratio and lower flexibility leads to a system with lower diffusivity. In addition, tracers in a network composed by nanofibrils with lower flexibility will have a higher probability of being trapped and hindered to diffuse through the network. Moreover, a threshold concentration of entanglement has been identified for both CNC and CNF networks. These findings offer new fundamental insights into nanoscale transport in crowded networks of flexible nanofibrils. Finally, the results can serve as a guideline for designing advanced bio-nanocomposites to be used in biomedical applications, such as smart drug delivery systems.

Understanding the role of flexibility and aspect ratio of nanofibers on transport phenomena in nanofibrous networks

ACS Spring 2022

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