Ricinoleic acid as a reagent in the synthesis of ionomeric copoly(ester-amide)s for water soluble coating applications

In this investigation, water-soluble coatings based on poly(ester-amide)s were applied to a commercial poly(ethylene terephthalate) (PET) film. In particular, poly(hexamethylene isophthalamide) (PA6I) was synthesized using 1,6-hexamethylene diamine (HMDA) and isophthalic acid (IPA). To impart water solubility to the material, 15 mol% of sulfonated groups was inserted along the macromolecular chain (PA6I/PA6ISO3). Additionally, 20 mol% of ricinoleic acid (RA) was introduced to potentially confer antimicrobial activity (PA6I/PA6ISO3/PRA). The PET-film coated with the prepared poly(ester-amide) shows potential for use in packaging and coating applications, particularly in the medical sector. The materials were characterized in terms of thermal properties by differential scanning calorimetry (DSC) and thermogravimetry (TGA), demonstrating high thermal stability and an amorphous nature. Mechanical properties were evaluated, and cytotoxicity tests were conducted using fibroblast cells. The results revealed significant improvements in elongation and strength at break compared to uncoated PET, suggesting good interfacial compatibility between the coating and the PET surface, as well as the absence of a toxic activity. Moreover, the presence of ricinoleic acid units conferred antibacterial activity, mainly against Listeria monocytogenes, a common foodborne pathogenic bacterium.