In Situ Synthesis of Conducting Polymers: A Novel Approach toward Polymer Thermoelectrics

Abstract

We report on a simple, fast, and versatile bottom-up strategy based on the solid-state synthesis of interpenetrating polymer network (IPN) films by the in situ oxidative polymerization of terthiophene (3T) with Cu(ClO 4 ) 2 inside poly(methyl methacrylate) after spin-coating. Our method allows the control of the polymerization of 3T and the doping degree with the Cu(ClO 4 ) 2 /3T molar ratio. We found that the electrical conductivity and Seebeck coefficient are uncorrelated. As Cu(II)/3T ratio increases, both the conductivity and Seebeck coefficient grow. We demonstrated that the uncorrelation is due to the enhancement of the carrier mobility at the macroscopic scale as the ratio increases. The resulting IPNs show conductivities up to 20 S/cm and a Seebeck coefficient of 110 μW K −1 . The highest power factor (18 μW m −1 K −2 ) was reached for a Cu(II)/3T ratio of 2.2. This approach is fully compatible with industrial coating techniques for the large-area printing and allows very fast screening of materials and formulations to optimize thermoelectric properties.

In Situ Synthesis of Polythiophene and Silver Nanoparticles within a PMMA Matrix: A Nanocomposite Approach to Thermoelectrics

“…However, the second percolation curve (yellow line in Figure a) shows a t -value of 0.91, suggesting a percolation in 2D. In our previous work, when Cu­(ClO 4 ) 2 was used as an oxidant agent, the resulting IPN film showed a single percolation with a t -value of 2.4 and a maximum conductivity (10 S cm –1 ) lower than that of Ag-PT-PMMA (120 S cm –1 ) . Below a value of 2.2 for the oxidant/monomer ratio, Cu­(II)-PT-PMMA and Ag-PT-PMMA IPNs show similar conductivities.…”

“…Recently, we reported on the thermoelectric properties of PT-PMMA IPN thin film . This synthetic approach allows the modification of the thermoelectric properties through the control of the polymerization process and the doping degree varying the oxidant salt/monomer molar ratio, showing electrical conductivities up to 20 S cm –1 and Seebeck coefficient of 110 μV K –1 .…”

“…This synthetic approach allows the modification of the thermoelectric properties through the control of the polymerization process and the doping degree varying the oxidant salt/monomer molar ratio, showing electrical conductivities up to 20 S cm –1 and Seebeck coefficient of 110 μV K –1 . However, these films showed low PFs (18 μW m –1 K –2 ) . A common approach to improve thermoelectric properties is using conducting polymers with nanostructured materials (carbon nanotubes, SnS, and Te, ...) to form a hybrid nanocomposite which produces an enhancement of the PF. − ,− Despite the recent progress on increasing ZT in conducting polymers and their nanocomposites, further research is still needed to improve their efficiency to compete with traditional thermoelectric materials.…”