Nanocellulose Films and Barriers

Nanoscaled cellulosic materials have an inherent tendency to form films upon drying. These films have unique physical properties: they are strong and they can appear as translucent or even fully transparent depending on the overall dimensions of the individual fibrils. They possess good thermal stability, smoothness, density, and chemical reactivity which make them as attractive templates for bioinspired functional materials. Since the topic in question is broad, this chapter concentrates on describing the characteristic features of films prepared using plant-derived cellulose nanofibers (CNFs). Other nanocellulosic materials, i.e., bacterial cellulose as well as cellulose nanocrystals are only cited with relevant references. The characteristic features described here include the mechanical behavior, surface roughness, and reactivity of nanofibrillated cellulose films. The larger attention is paid not only for the films' ability to act as oxygen and moisture barriers but also for their peculiar behavior in the presence of water molecules. Few relevant approaches to control the water sensitivity of the films are discussed.