Green chemical modification of cellulose presents a unique chemical challenge, especially from the vantage point of sustainable development that is favored by the use of wood fibers, heterogeneous conditions, and reactants and solvents of biobased relevance. However, heterogeneous conditions imply that cellulose is a supramolecular assembly whose composition and build-up depend on the initial source and pretreatments. Also, understanding reaction outcomes is accompanied by inherently challenging characterization. The key question is how we should design our reaction systems to achieve customizable and green functionalization of cellulose under heterogeneous conditions. To explore this, we selected never-dried high-content cellulose fibers (>96 % cellulose) as the substrate for the modification with three relevant biobased reactants (succinic, maleic, and crotonic anhydride), with BBIL-AcO as a biobased reactivity promoter. The reactions were performed under either high fiber swelling (basic) or low fiber swelling (acidic) heterogeneous conditions, and the outcome was analyzed in detail. The results unravel clear design strategies for controlling the reaction outcome during the green heterogeneous functionalization of cellulose and present clear synthetic strategies for using cellulose as the key substrate in the next generation of fully biobased and green materials.

The synthetic freedom to operate is highly dependent on the final application. In polymer science, scalable reactions, simple purification, and the ideal use of renewable and relevant precursors are relied on. This work explores the ring-opening of oxiranes with acrylic acid (AA) toward β-hydroxy acrylates; great care is given to the synthetic aspects of the transformation. In addition to its simplicity, and high yield (isolated yield 68%–87%), the methodology is scalable, atom-economic, and associated with simple purification. Dependent on the initial oxirane, access to a wide range of polymeric properties with a modulus ranging from 0.3 to 630 MPa, strength from 0.3 to 19 MPa, and elongation-at-break from 3% to 170% is demonstrated. All four polymers explored are thermally stable above 250 °C and highly transparent. This work emphasizes the potential of AA as a nucleophile for direct access to monomers for a wide range of polymer applications.

Cellulosic nanomaterials are ideal reinforcers in hydrogel composites, but the current techniques that ensure defined nano-dimensions reduce sustainability. A different strategy for the synthesis of hydrogels from pulp fibers using green chemistry could offer a more sustainable solution. This work explores a mild, straightforward chemical modification with maleic anhydride that simultaneously decorates the fibers with carboxylate and alkene groups. Tuning the temperature of the reaction enables control over the surface charge ranging from 150 to 1,000 μmol/g. The fibers are used to construct a rubber-like, water-stable hydrogel composite prepared by in situ telechelic PEG polymerization followed by thermal or UV-induced free radical crosslinking. The initiation strategy, molecular weight of telechelic PEG, and degree of modification of the fibers enable control over the network formation within and around the fibers. The hydrogel composite is designed to be hydrolytically degradable under alkaline conditions, allowing separate recovery of both fibers and polymer precursors.

Biopolymers, especially cellulose, are vital to transitioning to a circular economy and reducing our reliance on fossil fuels. However, for many applications a high degree of cellulose hydroxyl modification is necessary. The challenge is that the chemical features of the hydroxyls of cellulose and water are similar. Therefore, chemical modification of cellulose is often explored under non-aqueous conditions with systems that result in high hydroxyl accessibility and reduce cellulose aggregation. Unfortunately, these systems depend on hazardous and complex solvents from fossil resources, which diverge from the initial sustainability objectives. To address this, we developed three new betaine-based ionic liquids that are fully bio-based, scalable, and green. We found that a specific ionic liquid had the perfect chemical features for the chemical activation of cellulose without disturbing its crystalline ordering. The high activation in heterogeneous conditions was exemplified by reacting cellulose with succinic anhydride, resulting in more than 30 % conversion of all hydroxyls on cellulose. Overall, this work opens new perspectives for the derivatization of cellulosic materials while simultaneously “keeping it green”.