A series of alkyl-substituted and unsubstituted poly(3,4-alkylenedioxythiophene)s were synthesized electrochemically using 3,4-alkylenedioxythiophene derivative monomers where either the size of the alkylenedioxy ring or the nature of the pendent group was varied. The specific systems studied include 3,4-ethylenedioxythiophene (EDOT), 2-methyl-2,3dihydrothieno [3,4-b][1,4] (BuDOT-Xyl). Optoelectrochemical experiments revealed that the nature of the substitution on the polymers had little effect on the extent of conjugation of the backbone as evidenced by electronic band gaps for all polymers of approximately 1.7 eV (730 nm). These electrochromic polymers switch from a relatively transmissive light green in the oxidized form to an opaque dark blue in the reduced form, with the highest electrochromic contrast ratios accessible for PBuDOT and PEDOT-C 14 H 29 . Multiple switching studies monitoring the electrochromic contrast showed that ca. 300 nm thick polymer films could be fully switched between their reduced and oxidized forms in 0.8-2.2 s with ∆%T of 44-63%. In situ conductivity studies carried out on relatively thick polymer films (2.7-9.5 µm) deposited between large gap (200 µm) lateral growth electrodes demonstrated the lowpotential turn-on for these materials, and maximum conductivities of 0.2-12.1 S/cm were attained.

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Correlation analysis of the oxidation potentials of a series of N, N',3, substituted at the para positions of the outer phenyl rings shows a linear free energy relationship with resonance-enhanced substituent parameters (s ). Reaction parameters (r ) for oxidation of TPABs were found to be À1.53, À1.45 and À1.34 (per substituent) in methylene chloride, acetonitrile and propylene carbonate respectively. The resonance enhancement and small magnitude of the r values are related to a significant but weak delocalization of charge onto the outer phenyl rings in the molecular orbitals of radical cations resulting from the oxidation of TPABs. Data on the oxidation of p-substituted triphenylamines were treated similarly and gave a r value of À3.27 (per substituent) in acetonitrile, greater than that for TPABs owing to a more significant delocalization of charge onto the phenyl rings in the molecular orbitals of the corresponding radical cations. To demonstrate their predictive value, these linear free energy correlations were used to estimate the oxidation potentials of similarly substituted N, N,N',N',N@,N@-hexaphenyl-1,3,5-triaminobenzenes, which are of interest as building blocks for molecular magnetic materials.