In the last decades, the bio-based, biodegradable and eco-sustainable materials have irrupted in the panoram of the available options for different commercial and potential applications and have captured the interest of the researchers not only for the capability of replacing fuel-based raw materials, but for the new functionalities and properties that can be exploited
Plant-based materials have received considerable attenttion; plant oils, carbohydrates and proteins have all been used as starting materials for the synthesis of polymer-based goods. Starch and plant oils have had and protagonic role, but also the almost unmodified plant biomass, such as vegetable fibers that have been widely used mainly in the construction and automobile industries.
The main component of plants is cellulose , a carbohydrate with very useful properties, among which, its high crystallinity explains its high specific mechanical properties. This particular characteristic and its low density were the reasons for using vegetable fibers (natural composites with varying concentration of cellulose, lignin, hemicellulose and other minor components) as reinforcement of plastic composites, in the first place. Besides, cellulose fibers can be the source of very interesting and useful nanomaterials: microfibrillar cellulose and cellulose nanocrystals. Any of them can be used as main phases or as reinforcing phases in different composites. The applications are extremely varied and uses in nanoreinforced composites, strong papers, hydrogels, coatings, etc. have been reported or proposed.
In this presentation, the role of cellulose nanocrystals (CNC) from vegetable sources will be discussed, in particular as reinforcing materials for polyurethanes and bio-based polymeric matrices. Additionally, the capability of suspensions of cellulose nanocrystals to behave as liquid crystals will also be addressed, since this feature offers potential for the preparation of optically active films.