Synthesis, characterization, and thin‐film properties of 6‐oxoverdazyl polymers prepared by ring‐opening metathesis polymerization

Abstract

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 (Ð < 1.2) were produced. Thermal gravimetric analysis of a representative example of the title polymers demonstrated stability up to 190 °C, while differential scanning calorimetry studies revealed a glass transition temperature of 152 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,ox = 0.25 and E 1/2,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 m or more to 1.7  10 4 m and suggesting the potential usefulness of polymer 13 in bistable electronics.

Crystallographic Insights into the Synthesis and Magnetic Properties of Oxoverdazyl Radicals Functionalized by Benzoic Acid

“…The presence of these two processes is typical of neutral oxoverdazyl radicals. The values of the oxidation (0.37 V and 0.21 V for H I Me and H I i Pr , respectively) and reduction (–1.34 V and –1.47 V for H I Me and H I i Pr , respectively) potentials are consistent with those previously published , . The assignment of the processes is then straightforward.…”

“…Nonetheless, such irreversibility has been observed when various acids are willingly added to the solution, as well as in an imidazole‐substituted oxoverdazyl . When the acidic proton borne by the substituent of the verdazyl radical is replaced by a nonacidic group, the reversibility is recovered , . Following these observations, the irreversibility observed for H I Me and H I i Pr is attributed to the presence of the protonated carboxylic acid moiety of these radicals.…”

“…Verdazyl radicals have been known as stable organic radicals for a long time Their current revival follows two lines: the synthesis of purely organic materials with photoswitchable or conductive properties and their use as proligands for original coordination compounds , , . It turns out that the coordination chemistry of these radicals is rather tricky and tedious and is sometimes perturbed by the limited stability of the radicals.…”

“…To overcome the stability and solubility problems encountered during coordination processes, Brook et al have proposed the use of isopropyl groups, instead of the mostly used methyl groups . This strategy has since been used for introducing verdazyl radicals into polymers …”

“…[11] This strategy has since been used for introducing verdazyl radicals into polymers. [6] Herein, following this line, we compare the synthesis, as well as the structural and magnetic properties, of 1,5-dimethyl-3-(4′-the case of HI iPr , depending on the solvent, two polymorphs are crystallized. The structure resolution reveals that, in the solid state, the organization of the verdazyl radicals is governed by both H-bonding and π-π interactions and is reminiscent of the H-bonded structures that can be present in solution.…”