Poly(ester amide)s from biomass-based 3,4-dihydrocoumarine through Meldrum's acid mediated ketene chemistry

Meldrum's acid mediated ketene chemistry (MAMKC) is applied to synthesis of poly(ester amide)s in this work. An MA-functionalized phenolic amide compound (MA_PhOH-Am) is synthesized from the reaction between a MA-functionalized amine and 3,4-dihydrocoumarine (DHC, a biomass-based chemical) through amine-lactone addition reaction. Polymerization of MA_PhOH-Am results in the corresponding poly(ester amide) (P(Es-Am)), through MA thermolysis reaction (generating the corresponding ketene groups) and ketene-phenol addition reaction. Both MA_PhOH-Am and P(Es-Am) have been characterized with spectral methods and thermal analysis. P(Es-Am) has an inherent viscosity of 0.49 dL g⁻¹, a molecular weight of 76,500 Da, a glass transition temperature of 145°C (tanδ peak in dynamic mechanical analysis), a thermal stability of about 320°C, and a storage modulus at 50°C of 1.0 GPa. In the stress–strain measurement, P(Es-Am) exhibits a Young's modulus, a tensile strength, and an elongation at break of 10.6 ± 0.7 GPa, 165 ± 40 MPa, and 1.83 ± 0.41%, respectively. An effective approach for the synthesis of high-performance poly(ester amide)s has been demonstrated.