High‐Performance BioNylons from Itaconic and Amino Acids with Pepsin Degradability

Abstract The use of renewable feedstock for polymers has led to poor thermomechanical properties with high production costs. Herein, the production of novel chiral dicarboxylic acids derived from renewable itaconic and amino acids (d‐ or l‐leucine) is reported. In this study, rigid chiral heterocyclic dicarboxylic acid monomers are obtained with high purity from itaconic acid‐derived dimethyl itaconate as a starting material. Chirally interactive polyamides are prepared via melt polycondensation of hexamethylenediamine with heterocyclic diacid monomers. Further studies are conducted on d‐ or l‐leucine‐derived polyamides with homochirality that are fully amorphous. In contrast, the crystallization degree of the composite of d‐leucine‐derived polymer chains with l‐leucine‐derived chains increases to 36%, presumably due to enhanced interaction between polymer chains with different chiralities. The chirally‐interacting composite shows a glass transition temperature, T_g, of approximately 117 °C and a melting temperature, T_m, of approximately 213 °C, which are higher than those of conventional polyamides such as polyamide 11 (T_g of approximately 57 °C). The composite also shows high Young's moduli, E, and mechanical strengths σ, ranging from 2.2–3.8 GPa and 86–108 MPa, respectively. In addition, the polyamides show degradability with a digestive enzyme, pepsin.