Characterization of a vitrimer with methacrylate cellulose crosslinker for 3D printing

In the biomedical industry, polymers have been a real revolution due to their adjustable physicochemical properties and possibilities for biological functionalization, suitable for a wide range of applications. Depending on their chemical structure, they are divided into three macrocategories: thermoplastic polymers, hydrogels, and thermosetting polymers. The latter in particular are often used because of their excellent mechanical and thermal properties, good fatigue and creep resistance, and ease and speed of production. However, because of the irreversible chemical bonds created during the curing process, thermosets are inherently insoluble and infusible, making them particularly problematic in the recycling stage. For this reason, in recent decades, work has begun on a family of innovative polymers called CANs, which are formed from adaptable covalent networks capable of remolding due to external stimuli such as light or heat. This makes CANs materials with mechanical properties similar to thermoset polymers, but with recycling capabilities comparable to thermoplastic polymers. In 2011, Leibler and coworkers enriched this field by introducing the concept of vitrimers, cross-linked polymers in which covalent bonds can be redistributed within the network upon heating by associative exchange reactions, maintaining the integrity of the network. Since this seminal work, many research groups have begun to work on the theoretical backgroung of vitrimers, discovering new features such as shape memory, self-healing, and stimulus response. Recently, the idea of using biological materials in vitrimers has then been considered, as the natural components are truly sustainable, to further help reduce co2 emissions. To take a further step in this direction, the objective of this thesis is to study and characterize a vitrimer with methacrylate cellulose-based biological crosslinker, compared with a vitrimer with synthetic crosslinker, to evaluate any similarities or differences. Rheological and photoreological characteristics are studied by varying the percentages of biological crosslinker to define an ideal formulation printed by Digital Light Processing (DLP) photopolymerization technique. Extensive material analyses were conducted on this, including DSC, IR, swelling and %gel tests, combined with tensile tests to evaluate mechanical and self-healing characteristics after heat treatment. In the final stage of the work, the feasibility of printing anatomical bone components using the vitrimere analyzed was considered, with the aim of enabling simulations and mechanical testing steps in the biomedical field. This work opens the door to new studies and insights into the design of vitrimers with natural components.