The sulfonation of aromatic polymers such as polystyrene (PS), polyether sulfone (PES) and poly(ethylene terephthalate) (PET) is a commonly used industrial method to prepare sulfonated materials for ion-exchange resins, membranes, and electronics. This process operates in either a heterogeneous solid-gas reaction with sulfur trioxide or in concentrated sulfuric acid. These harsh conditions often lead to uncontrolled degrees of sulfonation, chain scission or crosslinking, and moderate regioselectivity. Instead, we found a sulfonation procedure that proceeds under mild conditions with a stoichiometric sulfonation reagent, 1,3-disulfonic acid imidazolium chloride ([Dsim]Cl). In this presentation, I will describe our optimization of the reaction conditions for the sulfonation of PS to maintain a similar polymer dispersity, without crosslinking or chain scission, and high degrees of sulfonation (&gt; 90%) and yields, and regeneration of the [Dsim]Cl. Analysis of the resulting poly(styrene sulfonate) (PSS) by <sup>13</sup>C NMR revealed over 99% regioselectivity for the para position thanks to the mild reaction conditions used. This reaction is applicable to a range of aromatic polymers, including PES, PET, thermoplastic elastomers such as styrene-ethylene-butylene-styrene, and expanded polystyrene waste obtained from plastic waste. We demonstrated that 60 to 74% of the plastic can be isolated from the sulfonation, with a degree of functionalization of 90%. Importantly, we proved that the upgraded PSS can be used in electronic applications by using them as matrix for the conductive polymer poly(3,4-ethylene dioxythiophene) (PEDOT) to form the conductive polyelectrolyte complex PEDOT:PSS. Materials thereby obtained perform at the same efficiency as commercial PEDOT:PSS in hybrid solar cells and organic electrochemical transistors, demonstrating a route towards plastic-to-electronics upcycling.

Mild and regioselective sulfonation of aromatic polymers including plastic waste

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