Sulfonation of low-density polyethylene (LDPE) films with fuming sulfuric acid was studied by X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance (ATR) infrared spectroscopy. The ATR spectra showed the formation of CAC double bonds and multiple sulfur atom containing groups for the sulfonation of LDPE films. This led us to propose that the abstraction reaction of hydride ion by sulfur trioxide (SO 3 ) in fuming sulfuric acid might account for the formation of the CAC double bonds. It was considered that after the abstraction reaction, these double bonds react with SO 3 , resulting in the production of alkene sulfonic acids and sultones, along with the formation of sulfate groups as a result of reaction of the double bonds with sulfuric acid. Experimental data by treatment of the sulfonated LDPE films with KOH and thiourea supported the proposed idea, estimating the approximate molar ratio of the products.

Summary: Sulfonation is one of the most commonly used methods for the surface modification of polymers. In this study, the sulfonation of poly(propylene) (PP) films with fuming sulfuric acid has been investigated with the focus on the surface reaction. Analysis of the sulfonated PP films by X‐ray photoelectron spectroscopy (XPS), attenuated total reflectance (ATR) infrared spectroscopy, and chemical modification demonstrated the formation of CC double bonds and sulfate groups in the sulfonation process. These results and a comparison with low‐density polyethylene (LDPE) films led us to propose a new sulfonation mechanism involving hydride abstraction and the formation of β‐sultones.

Summary: Photosulfonation of low‐density polyethylene (LDPE) films by UV irradiation in the presence of gaseous sulfur dioxide (SO2) and oxygen (O2) was studied by attenuated total reflectance (ATR) infrared spectroscopy and X‐ray photoelectron spectroscopy (XPS). The ATR and XPS analysis and chemical modification of UV‐irradiated LDPE films demonstrated the generation of CC double bonds and sultones in the reaction. These results indicated the possibility that sulfur trioxide (SO3) was produced during the photosulfonation. New pathways for the SO3 reaction with LDPE films, resulting in the formation of sulfonic acid groups, were proposed.Overview of the mechanism proposed for the photosulfonation of low‐density polyethylene by SO3 (produced upon UV‐irradiation of gaseous SO2 and O2).imageOverview of the mechanism proposed for the photosulfonation of low‐density polyethylene by SO3 (produced upon UV‐irradiation of gaseous SO2 and O2).