Lea‐Sophie Hornberger

In the context of green chemistry, replacing fossil‐based components with renewable alternatives in polymerization processes represents a key challenge towards more sustainable materials. This work establishes a terpene‐based polymerization system for the synthesis of aliphatic polyesters via yttrium‐mediated ring‐opening polymerization of bio‐based lactones. An aminoalkoxy bis(phenolate) yttrium catalyst was combined with terpene‐derived alcohols as nucleophiles and dl ‐limonene as a renewable solvent, replacing conventional systems based on isopropyl alcohol and toluene. The terpene‐based alcohols ( E )‐geraniol, (1 R ,2 S ,5 R )‐ l ‐menthol and (3 R )‐linalool, differing in steric demand and substitution pattern, were evaluated as initiators and chain transfer agents. Polymerizations of lactones with varying ring‐strain and size (β‐butyrolactone, ω‐pentadecalactone and the terpene‐derived (−)‐menthide) were performed and directly compared to fossil‐based reference systems. All monomers were successfully polymerized under fully terpene‐based conditions, yielding polymers with controllable molecular weights (3.2–44.6 kg mol ⁻¹ ), low dispersities ( Đ = 1.1–1.4) and defined end groups. Kinetic studies revealed a strong influence of nucleophile structure and concentration on polymerization characteristics, with increasing chain transfer agent content leading to decreased molecular weights, consistent with an immortal coordination‐insertion mechanism that can enable efficient catalyst utilization and reduced catalyst loadings. The fully terpene‐based systems provided comparable or improved control over the polymerization and end‐group analysis confirmed the incorporation of terpene‐derived initiating groups, enabling subsequent post‐polymerization functionalization via thiol‐ene chemistry. These results demonstrate that renewable nucleophiles and solvents can effectively replace fossil‐based components in rare‐earth metal‐catalyzed ring‐opening polymerization, providing access to sustainable and functionalizable aliphatic polyesters. © 2026 The Author(s). Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Terpenes exhibit a wide range of structures, thus enabling diverse applications. Herein, (‐)‐menthide and trans (+)‐carvomenthide were synthesized from terpenoids (‐)‐menthone and (+)‐dihydrocarvone, differing solely in their substitution pattern. (‐)‐Menthide features a methyl group at position 4 and an isopropyl group at position 7, whereas (+)‐carvomenthide shows the inverse arrangement. Both lactones were transformed into polyesters via ring‐opening polymerization (ROP) using an amino‐alkoxy‐bis(phenolate) yttrium catalyst. Polymerization kinetics revealed first‐order behavior, with (+)‐carvomenthide polymerizing significantly faster than (‐)‐menthide, while (‐)‐menthide demonstrated a more controlled polymerization. Activation energies were 36.3 kJ mol⁻¹ for (+)‐carvomenthide and 40.8 kJ mol⁻¹ for (‐)‐menthide. The Gibbs free energy of activation confirmed the lower energy barrier for (+)‐carvomenthide polymerization, with experimental values of 81.9 kJ mol⁻¹ compared to 89.1 kJ mol⁻¹ for (‐)‐menthide. Density functional theory (DFT) calculations supported the experimental results, with computed Gibbs free energy barriers of 84.5 kJ mol⁻¹ for trans (+)‐carvomenthide and 82.3 kJ mol⁻¹ for (‐)‐menthide and mechanistic differences. Refined free energy barriers were determined to be 102.1 kJ mol^⁻1 for (‐)‐menthide and 84.9 kJ mol^⁻1 for trans (+)‐carvomenthide, agreeing with the experimental trend. These findings highlight the critical role of molecular structure and substituent position on polymerization kinetics and energy barriers in metal‐catalyzed polymerization.