Mono‐Material Polydisulfides for Pressure Sensitive Adhesive Tapes With Closed‐Loop Recyclability

Abstract

ABSTRACT Conventional PSAs are multi‐layer materials that contain numerous additives, rendering them non‐recyclable. Efforts to develop more sustainable PSAs have predominantly focused on the adhesive layer with less attention toward the backing layer, which is typically a petroleum‐derived plastic. Herein, we report a strategy to create “mono‐material” PSA tapes from biogenic polydisulfide copolymers where both the plastic backing and adhesive layer are chemically recyclable. The copolymerization of α‐lipoic acid and its ester derivative, ethyl lipoate, yields high‐molecular‐weight polydisulfides ( M w > 400 kDa) with low glass transition temperatures (<−30 °C) and unique viscoelastic properties including extremely low moduli (<100 kPa) and exceptional adhesion strength (peel capacity > 400 N·m − 1 ) which was superior to commercial PSA tapes. The adhesive copolymer was treated with an alkaline solution to form a non‐adhesive ionomer congener that was 1000‐fold stiffer with plastic‐like mechanical properties. The ionomer backing and elastomeric adhesive layer were adhered without additives or compatibilizers to form a complete PSA tape. Furthermore, the entire tape was depolymerized to recover the original monomeric components and repolymerized to afford materials with comparable properties. These discoveries establish a fully closed‐loop, additive‐free PSA platform in which both the adhesive layer and backing originate from a single dynamic polymer.