Synthesis of castor oil-derived polyesters with antimicrobial activity

• Castor oil-derivatives are employed for the synthesis of bio-based polyesters.
• Polyesters obtained from ricinoleic acid exhibit high biocidal activity.
• Double bonds are exploited for grafting reaction to improve biocidal properties.

This work aims at preparing new castor oil-derived polyesters with antibacterial activity. Ricinoleic acid and 10-undecenoic acid, derived from castor oil, were successfully used for this purpose. Firstly, an unsaturated homopolymer, derived from the self-polycondensation of ricinoleic acid, and its copolymers with poly(butylene succinate) were synthesized and resulted to be characterized by a remarkable biocidal activity against Staphilococcus aureus and a medium efficiency against Escherichia coli. Secondly, a PE-like aliphatic polyester, the poly(hexamethylene succinate), has been modified at the chain ends with the presence of unsaturated units of 10-undecenoate. This polymer was characterized by a low biocidal activity, mainly against Gram-positive bacteria. Furthermore, for both these polymeric systems the presence of the double bonds has been successfully exploited to covalently link an antimicrobial molecule, a vinyl imidazolium salt, which significantly improved the biocidal performances of the final polymers. Therefore, a general method to link molecules to the double bonds of PRA and undecenoate units and to insert new specific functionalites to the castor oil-derived polyesters is here developed.

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