Enzyme­mediated tuning of cellulose surface reactivity for innovative compounding purposes

In recent decades, structural biopolymers produced from natural sources have gained popularity due to their outstanding properties. Cellulose, the most abundant biopolymer on Earth, is attracting attention because of its excellent physical and chemical properties, as well as being sustainable, renewable, and biodegradable. The intrinsic high crystallinity of cellulose makes it a promising reinforcing material in the formulation of elastomeric compounds. However, for certain applications, to ensure a good material compatibility, it is crucial to modulate the cellulose surface polarity and reactivity while preserving its crystalline structure. In this study, a lipase-mediated approach was employed to acylate cellulose hydroxyl groups. The formation of ester bonds was confirmed using Attenuated Total Reflectance Fourier-Transform Infrared (FTIR-ATR) analysis. Wide-Angle X-Ray Diffraction (WA-XRD) and Thermogravimetric Analysis (TGA) were used to verify the retention of crystallinity pattern and polymer thermal stability, respectively. Subsequently, cellulose modified with acrylic acid was incorporated into a model elastomeric compound using a peroxide-based vulcanization system. The mechanical properties of the compound were tested, resulting in a general reinforcement of the system. Compared to a control test, the elastomeric compound containing the modified polymer exhibited increased reinforcement and decreased energy dissipation, clearly indicating that a higher compatibilization of cellulose was achieved through acrylic acid functionalization. The use of functionalized cellulose as a reinforcing filler could offer several advantages over traditional fillers, including renewability, biodegradability, and reduced environmental impact. The enzymatic functionalization methodology developed in this work could pave the way for the development of a diverse spectrum of novel bio-based materials.