Enhancement of the Molecular Ordering via the Polymerization of 3,4-Ethylenedioxythiophene-Based Two-Monomer-Connected Precursor with 4,4-Biphenyldisulfonic Acid

The polymerization of 3,4-ethylenedioxythiophene (EDOT)-based two-monomer-connected precursors in various solvent systems leads to improved crystallinity, compared to poly(3,4-ethylenedioxythiophene) synthesized from traditional route. The P(EDOT:BPDSA:EDOT) is ordered by using 4,4-biphenyldisulfonic acid (BPDSA) that is a connector and dopant linking EDOT monomers. The crystallinity, measured from X-ray diffraction studies, is increased when using short chain or hydrophobic solvents. The crystallinity of P(EDOT:BPDSA:EDOT) significantly increases up to 45.0% compared to polymer with other sulfonic acids, bifunctional 1,2-ethanesulfonic acid, and monofunctional methanesulfonic acid (MSA). The crystal structure is also confirmed from high-voltage electron microscope. From these studies, it is confirmed that P(EDOT:BPDSA:EDOT) has an orthorhombic structure, which has the unit cell lattice parameters of a = 1.44 nm, b = 0.98 nm, and c = 1.18 nm from fast Fourier transform pattern images. The electrical conductivity is increased about four times with BPDSA (0.21 S cm(-1)) when compared using MSA (0.06 S cm(-1)).