Eventually, when the film reaches a certain thickness by the 40 th cycle, significantly exceeding the thickness of the interfacial region directly influenced by the applied Δ o w 𝜙, IET continues but the polymerisation reaction becomes purely chemical in nature and the 4electrode electrochemical cell can no longer detect the PEDOT thin film's continued growth, i.e., the CVs remain almost identical with further CV cycling as shown in Fig. for the 40 th , concentration will continue to oxidise the aqueous side of the PEDOT thin film. However, as the interfacial Ce 4+ concentration is no longer replenished as previously by an applied Δ o w 𝜙 positive of the PZC, with time the Ce 4+ is consumed, the kinetics of IET slows considerably (to an almost negligible rate after a certain time), and the potential of the PEDOT thin film falls until only oligomers may be oxidised due to the reduced driving force.