**8. Antioxidant Random Copolymers**

The synthesis of antioxidant copolymers such as dual-function amphiphilic random copolymers is critical to the suppression of medical-related infections through Fe2+ chelating ability and supra-macromolecular re-arrangement and morphological changes in hydrous environments and biocompatibility [95]. The polymerization of the tertiary amine-containing cationic monomer with hydroxyl-tyrosol yielded copolymers with ideal amphiphilic balances, molar ratios, and functional groups (especially the aromatic rings) for biomedical device coatings. In other cases, polypropylene (PP) antioxidant random copolymers have been proven useful in hot water applications in the presence of nucleating agents. Even though the utility of nucleating agents was not demonstrated by Taresco et al. [95], Grabmann et al. [96] argued that the compounds contributed to the modification of the crystalline structure—a factor that translated to higher thermal stability, mechanical strength (toughness and creep); this was observed in β-nucleated PP-R grades. In contrast, non-nucleated grades with α-crystal structure did not exhibit improvements in thermal and mechanical properties.

The utility of antioxidant random copolymers transcends biomedical devices to encompass food packaging applications, but the suitability of the materials for such applications is offset by the rapid depletion of antioxidants and chemical changes induced by microwave heating. Shahidi [97] observed that the viability of polymers for food preservation depends on the ability of natural antioxidants, additives, and preservatives to prevent rancidity—a process that impacts the odor and sensory appeal of foods.

Alin and Hakkarainen [98] explored the suitability of propylene-ethylene copolymer (PP-C), propylene-ethylene random copolymer (PP-R), and polypropylene homopolymer (PP) in plastic packaging containers labeled as microwave safe. The microwave testing of the polymers established the following. First, excessive heating (and subsequent analysis using microwave-assisted extraction (MAE) and HPLC) triggered the migration of the antioxidant molecules, particularly Irgafos 168 and 100 from the propylene-ethylene copolymer (PP-C), propylene-ethylene random copolymer (PP-R), and polypropylene homopolymer (PP) [98]. The migration resulted in unequal distribution of the antioxidants diminishing the utility of the polymer packaging materials in food packaging. A notable observation was the influence of polypropylene materials on the migration rate of the antioxidants and the inverse relationship with crystallinity. Better migration resistance was noted in the polypropylene homo-polymer (PP) potentially due to higher crystallinity [98]; this pattern remained unchanged despite contact with fatty acid stimulants. The influence of acetic acid and ethanol/iso-octane concentration on the rate of migration is depicted in Table 11.


**Table 11.** Antioxidant migration under microwaving and heating conditions.

In light of the preliminary observations made by Alin and Hakkarainen [98], polypropylene homo-polymer (PP) is an ideal alternative compared to propylene-ethylene copolymer (PP-C), propylene-ethylene random copolymer (PP-R), considering that the migration of antioxidants promotes toxicity and emergence of undesirable flavors [99]. A fundamental constraint moving forward was the development of packaging materials that are suitable and resistant to antioxidant migration, regardless of the fatty acid concentration in food. The experimental data shows that the composition of the food items, exposure to heat, and microwave energy predicts the chemical composition of antioxidant polymers for food packaging.
