Environmentally friendly upcycling of PHA-based copolymers

This work focuses on two fundamental aspects that make the use of plastics and, more recently, bioplastics sustainable and cyclical, namely their recycling and the valorization of the products resulting from this process. Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) was considered as substrate. A solventless partial chemical decomposition with concomitant branching was developed based on the use of reagents from renewable sources, namely pentaerythritol as polyalcohol and zinc stearate as catalyst. ¹H NMR, IR, and DSC measurements showed the formation of oligomers having a branched structure whose molecular weights and glass transition temperatures decreased with the increasing of the polyalcohol content in the reaction mixture. The oligomers were used as additives in the development of porous films based on the starting high molecular weight PHBH, exploiting a Non-Solvent Induced Phase Separation (NIPS) method using Cyrene®, a green solvent derived from cellulose. The ability of the films to retain a dye and the metal precursor palladium chloride was studied. In the latter case, the catalytic activity of the system consisting of Pd clusters formed on the porous substrate after the metal precursor reduction was demonstrated. Finally, the enzymatic hydrolysis of the films was evaluated using Humicola insolens Cutinase (HiC) at different concentrations and in different media.