Triggered Transience of Plastic Materials by a Single Electron Transfer Mechanism

Abstract

Transient polymers rapidly and controllably depolymerize in response to a specific trigger, typically by a chain-end unzipping mechanism. Triggers, such as heat, light, and chemical stimuli, are generally dependent on the chemistry of the polymer backbone or end groups. Single electron transfer (SET), in contrast to other triggering mechanisms, is achievable by various means including chemical, electrochemical, and photochemical oxidation or reduction. Here, we identify SET and subsequent mesolytic cleavage as the major thermal triggering mechanism of cyclic poly(phthalaldehyde) (cPPA) depolymerization. Multimodal SET triggering is demonstrated by both chemical and photoredox-triggered depolymerization of cPPA. Redox-active small molecules (p-chloranil and 1,3,5-trimethoxybenzene) were used to tune the depolymerization onset temperature of cPPA over the range 105−135 °C. Extending this mechanism to photoredox catalysis, N-methylacridinium hexafluorophosphate (NMAPF 6 ) was used to photochemically degrade cPPA in solution and thin films. Finally, we fabricated photodegradable cPPA monoliths with a storage modulus of 1.8 GPa and demonstrated complete depolymerization within 25 min of sunlight exposure. Sunlight-triggered depolymerization of cPPA is demonstrated and potentially useful for the manufacture of transient devices that vanish leaving little or no trace. Most importantly, this new mechanism is likely to inspire other SET-triggered transient polymers, whose development may address the ongoing crisis of plastic pollution.

Unravelling binder chemistry in sodium/potassium ion batteries for superior electrochemical performances

“…Actually, this defluorination of PVdF by sodium metal could be understood in terms of organic chemistry. 42–44 In our case, the most possible reaction is the single electron transfer (SET) reaction between PVdF and ether in the presence of Na + and e − (Scheme 1).…”

Green chemistry and the plastic pollution challenge: towards a circular economy

“…However, the ideal plastic packaging which combines required mechanical properties and cost-effectiveness with rapid triggered end-of-life degradation into naturally recyclable components remains an elusive goal and remains a substantial challenge for future research and development. 124 Interestingly, a recently published Royal Society of Chemistry White Paper on ' Science to enable sustainable plastics' from the 8 th Chemical Sciences and Society Summit (CS3) 125 discussed four major themes in sustainable plastics which align well with the cConclusions and oOutlook of this Perspective. These are (i) to understand the impact of plastics throughout their life cycles, (ii) to develop new sustainable plastics, (iii) closed-loop plastics recycling and (iv)…”

Residue analysis of thermally depolymerized phthalaldehyde‐based polymer thin films

“…At temperatures above T c , the polymer is thermodynamically driven to depolymerize but can exist in a metastable state as long as there are no reactive chain ends. These metastable polymers can undergo thermally induced chain scission to introduce reactive chain ends at temperatures higher than T c , such as >100°C 9,10 . Once a backbone bond is broken above T c and reactive chain ends are formed, the polymer can rapidly depolymerize from the solid state into volatile, low‐molecular‐weight products.…”

“…Although pPHA has been used for thermal probe lithography applications for over a decade, there is no study that examines the residue composition and amount that form after thermolysis of thin films 4 . Recently, Moore et al proposed that pPHA thermolysis followed a single electron transfer induced depolymerization to cleanly form o ‐phthalaldehyde monomer, 9 however, their residue analysis focused on bulk polymer samples and did not explore the non‐monomeric residues formed on the substrate surface. Identifying and quantifying the thin‐film residues that form on a substrate is important for semiconductor processing applications, especially for small critical dimensions, where trace amounts of residue could account for a substantial volume at the length scales considered or could alter the physical and electrical properties of surfaces.…”