Preparation of Block Copolymer-Stabilized Microspheres from Commercial Plastics and Their Use as Microplastic Proxies in Degradation Studies

This study presents a novel one-pot procedure for preparing sub-10 μm poly(ethylene glycol) (MPEG)-stabilized glycol-modified poly(ethylene terephthalate), poly(ethylene terephthalate) (PET), poly(lactic acid) (PLA), polycarbonate, and polycaprolactone (PCL) particles from commercial plastics. The prepared particles can be dried and directly resuspended in water, making them easy to handle and relevant mimics of microplastics. In addition, the method was extended to the preparation of unstabilized PET particles and somewhat larger polyethylene (PE)-based particles. Selected stabilized microparticles were subjected to aerobic biodegradation studies and compared with nonstabilized PET particles. All of the particles exhibited some degradation. For PLA and PET particles, the degradation corresponded well to the amount of surface-stabilizing MPEG groups or known impurities, confirming that these polymers do not degrade under the applied conditions but that the stabilizing groups do. PCL particles degraded relatively rapidly, which is consistent with the literature data and their relatively small size. PE-based particles degraded more than expected if only degradation of the stabilizing groups was taken into account, indicating that the surface chemistry of these particles plays a role in bulk degradation.