Thermoplastic polyester amides derived from oleic acid

Article abstract of DOI:10.1016/j.polymer.2011.08.002

Three lipid-based Polyester Amides (PEAs) with varying ratios of ester and amide linkages were synthesized. Oleic acid was used as the starting material to produce the intermediates, characterized by MS and NMR, used for polymerization. PEAs were characterized by FTIR and GPC. The PEAs were constrained to have similar number average molecular weights, in the 2 × 10⁴ range, thereby enabling comparison of their physical properties from a structural perspective. The thermal behavior of the polymers was assessed by DSC, DMA and TGA. Thermal degradation was not affected by ester/amide ratios, but T_g increased non-linearly with decreasing ester/amide ratios and correlated with hydrogen-bond density and repeating unit chain length. Crystallinity was studied by XRD and DSC. Degree of crystallization and multiple melting behavior as a function of cooling kinetics were explained well by hydrogen-bond density, repeating unit chain length and density of ester moieties. Mechanical properties were investigated by DMA and Tensile Analysis, with a non-linear increase of storage and tensile moduli recorded as a function of decreasing ester/amide ratios. The findings suggest how approaches to the synthesis of lipid-based PEAs can be targeted to the delivery of specific physical properties.