Thiol-ene ¿click¿ chemistry is very attractive as it enables rapid photo-polymerization reactions insensitive to oxygen presence and without side products generation, by irradiation with UV radiation. For this reason, a thiol-ene system was used in this thesis project as a polymer matrix for the production of composites. Despite this, thiol-ene polymers are characterized by very low mechanical properties. As a consequence, the aim of the thesis is the preparation of nancomposites containing cellulose nanofibrils (CNFs) as fillers in order to obtain higher mechanical performances. TEMPO-oxidized CNFs (TOCNFs) were used, due to their optimal dispersion in water, which allows them to maintain their nanometric dimensions without generating agglomerates, which is essential to maintain the transparency, typical of the chosen thiol-ene system.