Amidst declining fossil-based resources and environmental challenges, the focus on biobased materials has intensified. Carboxymethylation is one way to introduce reactive functionality to enhance the reactivity of lignin for a specified application. This research investigates the carboxymethylation of four lignin sources: eucalyptus kraft lignin, spruce kraft lignin, birch cyclic extracted organosolv lignin, and spruce cyclic extracted organosolv lignin. Our aim is to elucidate the role of the lignin structure in its reactivity. Using the advanced analytical techniques NMR spectroscopy, Fourier transform infrared spectroscopy, density functional theory, and size-exclusion chromatography, we provide a comprehensive characterization of the modified lignin. The findings offer valuable insights into how the chemical and physical properties of molecular lignin affect the selectivity and efficiency of the carboxymethylation reaction. These fundamental findings hold great potential for guiding considerations on the selection of lignin sources for specific applications based on their molecular properties.

The increased interest in the utilization of lignin in biobased applications is evident from the rise in lignin valorization studies. The present study explores the responsiveness of lignin toward oxidative valorization using acetic acid and hydrogen peroxide. The pristine lignins and their oxidized equivalents were analyzed comprehensively using NMR and SEC. The study revealed ring opening of phenolic rings yielding muconic acid- and ester-end groups and side-chain oxidations of the benzylic hydroxyls. Syringyl units were more responsive to these reactions than guaiacyl units. The high selectivity of the reaction yielded oligomeric oxidation products with a narrower dispersity than pristine lignins. Mild alkaline hydrolysis of methyl esters enhanced the carboxylic acid content of oxidized lignin, presenting the potential to adjust the carboxylic acid content of lignin. While oxidation reactions in lignin valorization are well documented, this study showed the feasibility of employing optimized oxidation conditions to engineer tailored lignin-based material precursors.

The ring-opening copolymerization (ROcoP) of epoxides and anhydrides is exploited to afford 4 structurally diverse and functional copolyesters. Mixtures of 2 epoxides (allyl glycidyl ether and butylene oxide) with 1 anhydride (succinic, glutaric, phthalic and homo phthalic anhydride) are copolymerized in the presence of bis (triphenylphosphine)iminium chloride (PPNCl) as organocatalyst. All monomer combinations yield vinyl-functionalized materials with alternating epoxide-anhydride units, statistical incorporation of both epoxides along the polymer chain and molar masses up to 28.3 kg/mol. The copolyesters are amorphous with a Tg between -39 degrees C and 38 degrees C. Together with the molar mass, the anhydride dictates the thermal stability of the copolyesters with glutaric anhydride resulting in a remarkably high thermal stability up to 310 degrees C. In a post-polymerization step, the pendant double bonds are radically crosslinked to gels with swelling ratios above 1500 % and com-parable to enhanced thermal stability with respect to the non-crosslinked, parent copolyesters. The degradation of the 4 copolyesters (before and after crosslinking) is tested in abiotic and enzymatic conditions: The highest degradation rates are observed for the non-crosslinked materials in enzymatic conditions with a mass loss of up to 60 % after 27 d. After crosslinking, the gels are more stable against degradation under both conditions, although a decrease in the gel content and a decrease in mass indicates that degradation still takes place.

Polymers containing ester bonds undergo abiotic degradation independently from the surrounding environment as long as the hydrolytic conditions are provided. The hydrolysis of the ester bonds leads a bulk degradation of the polymeric matrix which, contrary to surface erosion, is unpredictable. The enchainment of diverse degradability functions was sought to expand the scope of the degradation mechanism and achieve a more predictable profile of the mass loss.The copolymerization of trimethylene carbonate and p-dioxanone enabled the synthesis of one class of copolymers with controllable erosion rate and susceptible to three degradation pathways depending on the surrounding environment. The synthetic strategy used organocatalysts and allowed the synthesis at room temperature of both random and block copolymers in high yield and with molar mass, Mn, in the range 12-22 kg mol- 1. The composition and microstructure of the random copolymers were regulated by varying the monomers' ratio. Diverse cleavable groups, i.e., ester/ether and carbonate bonds, were statistically incorporated along the same polymer chain to yield materials able to degrade under hydrolytic, oxidative and enzymatic conditions. Bulk degradation was the mechanism that took place under hydrolytic conditions, while the oxidative and enzymatic environments lead to surface erosion. The rate of mass loss of the random copolymers was regulated by varying the composition. These results showed how the statistical incorporation of different degradable bonds could pave the way to diverse and more predictable degradation pathways than simple hydrolysis by taking advantages of the surrounding environment to trigger surface erosion.