A new viewpoint on aging degradation of polystyrene: From the perspective of molecular weight

In the photo-oxidative aging experiments, the observed trend of the molecular weight of polystyrene (PS) differs from the expected results. By utilizing techniques such as GPC, XPS, SEM, and UV–Vis, it has been demonstrated that the molecular weight of the PS surface decreases during the initial stages of aging, but remains stable in the later stages. The stability in molecular weight is closely associated with the presence of degradation products on the surface of PS. During the experiment, the low molecular weight PS short chains dissolve in the droplets produced by the aging machine, resulting in a reduction of low molecular weight PS chains on the surface. This phenomenon contributes to the maintenance of a stable molecular weight in the later stages. Additionally, this paper introduces a novel method for describing the degree of PS aging, which offers a more intuitive understanding of the degradation process. This method focuses on the number of special patterns obtained through etching away the degradation products, having reference value.