Solution processible statistical poly(3-methoxythiophene)-co-poly(3-hexylthiophene) copolymer

Abstract

Growing energy demand is provoking researchers to investigate semiconducting polymers for use in a wide variety of applications such as organic-based thermoelectric generators, solar panels, and thin-film transistors. Polythiophene has attracted wide interest in organic-based electronics due to the high stability of its (un)doped states, ease of structural modification, and solution processability. Herein, is described the synthesis of a thiophene monomer, 3-methoxythiophene, and its polymerization, (poly(3-methoxythiophene)) (PMoT), and statistical copolymerization with 3-hexylthiophene, poly((3-methoxythiophene)-co-(3-hexylthiophene)) (PMoT-P3HT), using Grignard Metathesis polymerization in place of more traditional electropolymerization of alkoxy thiophenes. 3-methoxythiophene synthesis is verified at each intermediate step using 1H NMR spectroscopy. PMoT-P3HT exhibited improved solubility in common organic solvents over PMoT due to the presence of the alkyl side chain. Analysis using the Spano model reveals PMoT-P3HT has a similar optical band gap and stretching mode energy to P3HT while absorbing a greater portion of the UV spectrum. Quantum chemical calculations by way of Density Functional Theory (DFT) were used to estimate polymer structures and electronic properties, which were found to capture experimental trends very well.