Synthesis of bio-based polymacrolactones with pendant eugenol moieties as novel antimicrobial thermoplastic materials

In the last few decades there has been a continuous effort toward the synthesis of polymers from renewable resources. In this context we have presently developed novel and fully bio-based functionalized polymacrolactones bearing pendant eugenol moieties. These polymeric materials were obtained by exploiting the ring-opening copolymerization of two macrolactones, ω-6-hexadecenlactone (6HDL) and ω-pentadecalactone (PDL), both derived from renewable resources, in the presence of a pyridylamidozinc(II) complex, to produce random poly(6HDL-co-PDL) copolymers. Eugenol, a natural occurring essential oil with anti-microbial properties, was modified in its mercapto derivative, the 4-(3-mercaptopropyl)-2-methoxyphenol (TE). Subsequently, the thiol-ene addition reaction of the TE to the CC double bond of the 6HDL monomeric units of the poly(6HDL-co-PDL) copolymers produced the functionalized polymacrolactones with pendant eugenol moieties. This synthetic approach allowed to modulate the amount of eugenol pendant groups on the polymeric chains. The melting temperatures and the thermal degradation behavior of the TE-functionalized copolymers were dependent on the copolymers composition. The antimicrobial activity of TE-functionalized copolymers was tested for the bacterium E. coli on films. The toxicity of the samples was dependent on the amount of TE groups in the films. Our approach demonstrated the feasibility to covalently attach eugenol moieties to a polymacrolactone main chain and to impart antimicrobial properties to the macromolecular chains.