Synthesis, Characterization, and Thin-Film Properties of 6-Oxoverdazyl Polymers Prepared by Ring-Opening Metathesis Polymerization

Redox-active 6-oxoverdazyl polymers were synthesized via ring-opening metathesis polymerization (ROMP) and their solution, bulk, and thin-film properties investigated. Detailed studies of the ROMP method employed confirmed that stable radical polymers with controlled molecular weights and narrow molecular weight distributions (D < 1.2) were produced. Thermal gravimetric analysis of a representative example of the title polymers demonstrated stability up to 190 degrees C, while differential scanning calorimetry studies revealed a glass transition temperature of 152 degrees C. Comparison of the spectra of 6-oxoverdazyl monomer 12 and polymer 13, including FT-IR, UV-vis absorption, and electron paramagnetic resonance spectroscopy, was used to confirm the tolerance of the ROMP mechanism for the 6-oxoverdazyl radical both qualitatively and quantitatively. Cyclic voltammetry studies demonstrated the ambipolar redox properties of polymer 13 (E-1/2,E-ox = 0.25 and E-1/2,E-red = -1.35 V relative to ferrocene/ferrocenium), which were consistent with those of monomer 12. The charge transport properties of thin films of polymer 13 were studied before and after a potential of 5 V was applied, revealing a drastic drop in the resistivity from 10(6) - 10(10) Omega m or more to 1.7 x 10(4) Omega m and suggesting the potential usefulness of polymer 13 in bistable electronics. (C) 2016 Wiley Periodicals, Inc.