End-capping of conductive poly(3.4-ethylene)dioxy-thiophene chain using 2-thienylmethyl methacrylate monomer

Structure of poly(3.4-ethylene)dioxythiophene (PEDOT) has been modified by end-capping the chain using a thiophene base monomer. End-capping was carried out to study the effect of PEDOT structures on the conductivity of the PEDOT/PSS films. The monomer used for the end-capping was 2-thienylmethyl methacrylate (2TMM). Endcapping of PEDOT with 2TMM was achieved by oxidative polymerisation of 3.4-ethylenedioxythiophene (EDOT) monomer in the presence of PSS as a dopant in aqueous solvent, and Na₂S₂O₈ and Fe₂(SO₄)₃ as oxidation agents. The reactions performed using ratio EDOT:PSS of 1:2.5, with the addition of varying concentrations of end capping agent: 10%, 20%, 30%, 40% and 50% by weight with respect to the EDOT monomer. Chemical characterisations of the structures were analysed using NMR and FTIR. PEDOT/PSS dispersions were also analysed using dynamic light scattering (DLS), capillary electrophoresis (CE), scanning electron microscopy (SEM), and conductivity measurements using the four point probe method. The results showed that the end-capping PEDOT was successfully employed using 2TMM monomer. The higher ratio of end-capping agent resulted in smaller PEDOT as indicated by CE and DLS results. Films surface were smoother with an increase in the ratio of end-capping monomer. While the conductivities of the films decreased with an increase in the ratio of 2TMM monomer.