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.

The cradle-to-cradle philosophy is desirable for semi-structural cellulose biocomposites. Selective chemical recycling of a thermoset matrix back to reusable monomers was realized while avoiding cellulose fiber degradation. A fully biosourced, PLA-based (polylactic acid) thermoset polymer was molecularly designed for chemical recycling and for curing in chemically heterogeneous plant fiber networks. Curing was by stepwise polymerization of 4-arm functional prepolymers of PLA in a cellulosic wood fiber network of high fiber content. FT-IR data supported covalent fiber/matrix interface bonding. These eco-friendly biocomposites showed high modulus (24 GPa) and high optical transmittance. The matrix was selectively degraded back to the initial building block, lactic acid monomer, under alkali conditions. This progressed without apparent damage to the cellulosic fibers. The green metrics of the synthesis showed strong potential for this material concept in a circular economy.

Translucent wood fiber composites offer new functions to stiff composites. Most "eco-friendly" thermoset resins are only partially biobased. Poly(limonene acrylate), PLIMA, can be fully biobased and is combined with hot-pressed softwood fibers (WF) by liquid resin impregnation and curing. Fibers are random-in-plane or strongly oriented and have different lignin characteristics. Microstructure-mechanical property relationships are compared for hot-pressed WF networks and WF/PLIMA biocomposites from the same fibers. Stress transfer in WF/PLIMA biocomposites is enhanced with a modulus of up to 16.7 GPa and a tensile strength of up to 139 MPa, compared to transparent plastics like poly(methyl methacrylate) (modulus similar to 3 GPa, tensile strength similar to 70 MPa). Optical transmittance is high, even at 35 vol % fiber content, suggesting translucent panels or lighting applications. Eco-indicators show that the PLIMA matrix accounts for similar to 80% of biocomposite cumulative energy demand (CED, cradle to gate) of 60 MJ/kg, compared to similar to 120 MJ/kg for glass fiber/thermoset composites.

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”.

Maleated kraft lignin has been explored as a building block for degradable thermosets. The maleation procedure allows for a facile and atom-efficient way to install functional handles into the lignin structure, rendering the obtained lignin amenable for cross-linking via amine-Michael addition and thiol-ene coupling. Since lignin modification leads to the formation of an ester linkage, the final thermosets are susceptible to hydrolytic degradation, demonstrated under basic conditions (NaOH, 0.6 M, acetone/water (1/2.5, v/v) for 2.5 h at 75 °C). We also extended the study to biocomposite formulations with cellulose nanofibrils as reinforcing agents. The final biocomposites demonstrated strengths of 110-150 MPa and moduli of 4-5.5 GPa at 55-65 wt % of nanocellulose. This work offers a cradle-to-grave approach for biobased and degradable thermosets and composites from technical lignin.

Defined macromolecular architecture using anionic ring-opening copolymerization (ROcP) of lactones and cyclic carbonates offers facile routes toward copolymers with unique material properties, ranging from thermoplastic to elastomeric. However, monomers with a slow ROP rate are hampered by competing backbiting reactions, scrambling the macromolecular sequence, and, thereby, a loss of material properties occurs. We here solve this issue by controlling the rate of backbiting. Through our approach, we show how block structures previously inaccessible can be synthesized from monomers with vastly different ROP rates, covering small lactones and even including macrolactones. This control can also be extended beyond block structures to include random and gradient architectures by tuning monomer concentration to the relative ROP and backbiting rate.

Designing the next generation of circular plastics can contribute to preventing environmental pollution and the loss of embedded value. In light of this, assessing the thermodynamic parameters, i.e., the polymerization enthalpy (ΔH<inf>p</inf>) and entropy (ΔS<inf>p</inf>) of ring-opening polymerization, is becoming increasingly important as these directly connect to the chemical recyclability of polymers. However, determining the thermodynamics currently requires the synthesis of each monomer and polymer structure, consuming large amounts of time and chemicals, making it unfeasible to screen a myriad of different structures to find polymers with optimal properties and recyclability. In silico methods could mitigate these issues and drastically increase the rate at which new recyclable plastics can be developed. We demonstrate how the collision frequency between the reactive groups in polymers and monomers, derived from nonreactive (i.e., no chemical changes) molecular dynamics simulations, can be used for the simultaneous computation of ΔH<inf>p</inf> and ΔS<inf>p</inf> with respective 3.5 kJ mol^-1 and 6.7 J mol^-1 K^-1 average deviation from experimental data.

The high structural anisotropy and colloidal stability of cellulose nanofibrils' enable the creation of self-standing fibrillar hydrogel networks at very low solid contents. Adding methacrylate moieties on the surface of TEMPO oxidized CNFs allows the formation of more robust covalently crosslinked networks by free radical polymerization of acrylic monomers, exploiting the mechanical properties of these networks more efficiently. This technique yields strong and elastic networks but with an undefined network structure. In this work, we use acrylate-capped telechelic polymers derived from the step-growth polymerization of PEG diacrylate and dithiothreitol to crosslink methacrylated TEMPO-oxidized cellulose nanofibrils (MATO CNF). This combination resulted in flexible and strong hydrogels, as observed through rheological studies, compression and tensile loading. The structure and mechanical properties of these hydrogel networks were found to depend on the dimensions of the CNFs and polymer crosslinkers. The structure of the networks and the role of individual components were evaluated with SAXS (Small-Angle X-ray Scattering) and photo-rheology. A thorough understanding of hybrid CNF/polymer networks and how to best exploit the capacity of these networks enable further advancement of cellulose-based materials for applications in packaging, soft robotics, and biomedical engineering.

To address the increasing demand for biobased materials, lignin-derived ferulic acid (FA) is a promising candidate. In this study, an FA-derived styrene-like monomer, referred to as 2-methoxy-4-vinylphenol (MVP), was used as the platform to prepare functional monomers for radical polymerizations. Hydrophobic biobased monomers derived from MVP were polymerized via solution and emulsion polymerization resulting in homo- and copolymers with a wide range of thermal properties, thus showcasing their potential in thermoplastic applications. Moreover, divinylbenzene (DVB)-like monomers were prepared from MVP by varying the aliphatic chain length between the MVP units. These biobased monomers were thermally crosslinked with thiol-bearing reagents to produce thermosets with different crosslinking densities in order to demonstrate their thermosetting applications. The results of this study expand the scope of MVP-derived monomers that can be used in free-radical polymerizations toward the preparation of new biobased and functional materials from lignin.

The thermodynamic equilibrium between ring-opening polymerization and ring-closing depolymerization is influenced by monomer-solvent-polymer interactions, an effect that can be utilized to promote chemical recycling to monomer. Here, the influence of monomer structure on this solvent effect has been investigated, showing that the chemical structure of the monomer influences the power of the solvent to supress the ceiling temperature. The study also demonstrates how catalyst selectivity can be utilized to obtain selective ring-closing depolymerization of one component of a polymer blend, even when the thermodynamics dictate otherwise.