Certain food packaging may possess antibacterial functions through the adsorption of small molecules. However, during the course of their manufacture at high temperatures, or even over time, these molecules are released and contaminate the food.

In collaboration with the INRAE-AgroParisTech, chemists from Iramis have proposed an alternative path that does not involve any untimely releases, and which utilizes covalent (and therefore stable) bonds between the packaging and an antibacterial polymer.

For the bactericide, they chose polyionene polymers that contain positive charges, separated by hydrophobic segments of an adjustable size.

They first developed a process for grafting these polymers onto glass, comprising three steps in the liquid phase: polydopamine deposition; polymerization induced by diazonium salts; and finally, the polyaddition of ionenes (C₁₃H₁₈). Each of these steps was characterized in detail using various surface analysis techniques.

In parallel, they synthesized several polyionenes by varying the length and nature of their segments (aliphatics and ethers), as well as their molecular weight, and evaluated their antibacterial action and cytotoxicity. Polymers with (CH₂)n aliphatic segments were found to be the most bacteriostatic, and revealed increasing efficacy with segment length.

As part of the BRICAPAC project supported by the ANR, three processes were developed to incorporate polyionenes into polyethylene food films.

• The first one transposes the process to glass with polyethylene.
• The second uses printing with a polyionene-based ink, followed by UV exposure.
• The third, studied in collaboration with BOLLORE Division Films Plastiques, consists in incorporating the polyionenes via a "master mix" during the extrusion of the polyethylene film.