Upcycling Poly(vinyl chloride) and Polystyrene Plastics Using Photothermal Conversion

Abstract

Poly(vinyl chloride) (PVC) and polystyrene (PS) are among the least recycled plastics. In this work, we developed a simple and novel strategy to valorize PVC and PS plastics via photothermal conversion to (1-chloroethyl)benzene, a commodity chemical with excellent versatility. As PVC is known to release HCl gas and decompose into conjugated polyenes, we envisioned a dual role for PVC plastics. While the in situ-generated HCl serves as a chlorine source, the resulting dehydrochlorinated-PVC (DHPVC) functions as a photothermal agent to accelerate the hydrochlorination of styrene. We converted PVC and styrene in up to 89% (1-chloroethyl)benzene in less than 1 h of white light irradiation. Subsequent nucleophilic substitution on the chloro-adduct formed 1-phenylethanol (a fragrance additive) and fendiline (a heart disease drug) in high yields. The PVC photothermal hydrochlorination system is applied to various alkenes and is compatible with post-consumer waste PVC plastics and plasticizers. Ultimately, PVC upcycling with photothermally recycled styrene achieved 84% (1-chloroethyl)benzene under white LED light in 1 h, and co-upcycling of PS and PVC achieved 42% yield under focused sunlight irradiation in just 4 min.