Electrocatalytic Depolymerization of Self-Immolative Poly(Dithiothreitol) Derivatives

We report the use of electrogenerated anthraquinone radical anion (AQ center dot(-)) to trigger fast catalytic depolymerization of polymers derived from poly(dithiothreitol) (pDTT)-a self-immolative polymer (SIP) with a backbone of dithiothreitols connected with disulfide bonds and end-capped via disulfide bonds to pyridyl groups. The pDTT derivatives studied include polymers with simple thiohexyl end-caps or modified with AQ or methyl groups by Steglich esterification. All polymers were shown to be depolymerized using catalytic amounts of electrons delivered by AQ center dot(-). For pDTT, as little as 0.2 electrons per polymer chain was needed to achieve complete depolymerization. We hypothesize that the reaction proceeds with AQ center dot(-) as an electron carrier (either molecularly or as a pendant group), which transfers an electron to a disulfide bond in the polymer in a dissociative manner, generating a thiyl radical and a thiolate. The rapid and catalytic depolymerization is driven by thiyl radicals attacking other disulfide bonds internally or between pDTT chains in a chain reaction. Electrochemical triggering works as a general method for initiating depolymerization of pDTT derivatives and may likely also be used for depolymerization of other disulfide polymers.

Automated summary

We report the use of AQ center dot(-) as an electron carrier to trigger the catalytic depolymerization of pDTT polymers. The reaction is rapid and catalytic, with as little as a small amount of electrons needed for complete depolymerization. It is driven by thiyl radicals attacking disulfide bonds internally or between chains.