A solid-state NMR investigation of the dopability of poly(p-phenylene vinylene) model compounds and corresponding polymers with iodine

Abstract

Twelve phenylene vinylene compounds, including poly(p-phenylene vinylene) (PPV), poly(2,5-dimethoxyphenylene vinylene) and the copolymer of PPV and poly(2,5-dimethoxyphenylene vinylene), have been prepared and doped with iodine to form electrically conducting materials. Characterization of the molecular structure and conductivity as a function of the dopant level for trans,trans-1,4-bis(2-(3,4,5-trimethoxyphenyl)ethenyl)benzene (MPV4) and trans-3,4,4',5-tetramethoxystilbene (MPV7) were carried out. Methoxy groups in a para position on the terminal rings contribute more to the conductivity than meta-substituted methoxy groups. This correlates well with the spectral changes that occur in the CP/MAS C-13 spectra upon doping. Conductivity measurements on trans-stilbene (MPV8), trans, trans-distyrylbenzene (MPV9) and all-trans PPV show a slight chain length dependency. Upon doping with iodine, cis-trans mixtures of MPV4 are converted to trans, trans isomers, and the original double bond configuration does not affect the conductivity.