Preparation of block copolymer-stabilised microspheres of common polymers and their use as microplastics proxies in degradation studies

Abstract

The environmental fate and impact of microplastics as well as their possible physiological effects, are expected to depend on their physico-chemical characteristics, including polymer types and surface chemistry. There is thus a clear need to develop a broad range of model microplastic particles to study the fate and effects of environmentally relevant microplastics. Here, a simple one-pot procedure to prepare sub-10 µm poly(ethylene glycol) (MPEG)-stabilised glycol modified poly(ethylene terephthalate) (PETG), poly(ethylene terephthalate) (PET), poly(lactic acid) (PLA), polycarbonate (PC) and polycaprolactone (PCL) particles is described. The prepared particles can be dried and directly re-suspended in water, making them easy to handle and relevant mimics of microplastics. In addition the method was extended to prepare somewhat larger polyethylene-based (PE) particles and control PET particles were also prepared. Selected microparticles were subjected to aerobic biodegradation studies and compared with non-stabilised PET particles. All particles exhibited some degradation. For PLA and PET particles, the degradation corresponded well to the amount of surface stabilising MPEG groups or known impurities, confirming that these polymers do not degrade under the applied conditions but that the stabilising groups do. PCL particles degraded relatively rapidly, consistent with literature data and their relatively small size. PE-based particles degraded more than expected if only degradation of the stabilising groups was taken into account, indicating that the surface chemistry of these particles plays a role in bulk degradation. These studies thus demonstrate the effect of varying the type of polymer and improves the understanding of how surface chemistry affects the degradation of microparticles.