Electrochemical Characterization of Redox Probes Confined in 3D Conducting Polymer Networks

In this manuscript we present a versatile platform for introducing functional redox species into tailor-made 3D redox polymer networks. Electrochemical characterization based on cyclic voltammetry is applied to verify the immobilization of the redox species within the conducting networks. Ultimately this strategy shall be extended to (photo)electrocatalytic applications which will profit from the conducting polymer matrix. Soluble precursor copolymers are synthesized via radical copolymerization of vinyltriphenylamine (VTPA) with chloromethylstyrene (CMS) in different ratios, whereas CMS is subsequently converted into azidomethylstyrene (AMS) to yield poly(VTPA-co-AMS) copolymers. Spin-coating of poly(VTPA-co-AMS) on gold electrodes yields thin films which are converted into stable polymer network structures by electrochemical crosslinking of the polymer chains via their pendant triphenylamine groups to yield N,N,N',N'-tetraphenylbenzidine (TPB) crosslinking points. Finally, the resulting redox-active, TPB-crosslinked films are functionalized with ethynylferrocene (EFc) as a representative redox probe using a click reaction. Main experimental tools are polarization modulation infrared reflection absorption spectroscopy and scan rate dependent cyclic voltammetry. Especially the latter proves the successful conversion and the immobilization of redox probes in the polymer matrix. The results are compared with the reference system of azide-terminated self-assembled monolayers on gold substrates, allowing to distinguish between free and immobilized EFc species.