High Precision Tuning of Limonene Polyamide via Side-Chain Functionalization for Specialized Applications

Abstract

Despite the success of conventional nylons in biomedicine, there is a growing demand for specialized materials tailored to modern needs. Tunable and sustainable bio-polyamides (PAs) derived from terpenes offer a promising alternative. This work focuses on limonene polyamide (LiPA) synthesized via anionic ring-opening polymerization (AROP) from limonene lactam and its functionalization via a thiol-ene click reaction. Optimizing the AROP enables the preparation of high molecular weight LiPA up to 54 kg mol−1, rendering the material attractive for further utilization. Subsequent exploration of the side-chain functionalization via thiol-ene click chemistry allows for the introduction of diverse functional groups (e.g., alkyl, ester, sulfonate) and finetuning of the polymers’ properties. The modifications give control over solubility, processability, hydrophilicity, and glass transition temperature (44–133 °C). While alkyl groups increase hydrophobicity, all PAs display hydrophilic surfaces (q < 90°). Notably, the sulfonate-modified LiPA shows amphiphilic behavior, forming micelles in an aqueous solution, demonstrating potential for drug delivery applications. The high tolerance of the thiol-ene reaction towards various functional groups enables future incorporation of bioactive moieties, like cell-binding motifs for tissue engineering. In summary, this investigation demonstrates the tunability of LiPA’s properties through strategic side-chain modifications, paving the way for diverse biomedical applications.