Plastics Biodegradation Triggering by Surface Chemical Modification and Introduction of Antimicrobial Quaternary Ammonium Cations

The surface of films of poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate] (PHBH), a biodegradable polyester, was oxidized using photoactivated chlorine dioxide radical gas, generating carboxyl groups for the introduction of quaternary ammonium cations, namely crystal violet. Crystal violet was stable in deionized water but was desorbed through cation exchange in high-salinity media. In soil, the antimicrobial activity of crystal violet inhibited the biodegradation of PHBH films. In seawater, crystal violet was immediately desorbed from the film, which triggered the biodegradation of PHBH films, and biodegradation was also observed in freshwater. Therefore, by introducing crystal violet to the surface of PHBH films, we have developed a material that is stable in soil but degrades when released into aqueous environments, expanding the potential applications of PHBH in our daily lives such as agricultural equipment and outdoor gear.