Upcycling Poly(vinyl chloride) and Polystyrene Plastics Using Photothermal Conversion
Hanning Jiang, Erik A. Medina, Erin E. Stache
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.