Electronic Spectroscopy of Poly(Propylmethylazine)

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Poly(propylmethylazine) ([N═C(R1)—C(R2)═N]x, R1 ═ CH3, R2 ═ CH2CH2CH3, PMPAZ) and a permethylpolyazine (MMPAZ)-PMPAZ copolymer series with varying amounts of propyl substitution has been studied by UV-vis spectroscopy in solution and UV-vis-NIR as thin films and I2-doped thin films. The presence of the propyl group allows for limited solubility in some organic solvents but does not affect the approximate C2h symmetry of the conjugated π backbone indicative of substantial σ-π separability. Due to the two imine bonds in the repeat unit the electronic manifold contains two high-lying filled bands and two low-lying empty bands. The pristine polymers all exhibit a π → π* multiplet arising from the conjugated azine moiety with maxima observed approximately at 280 and 320 nm arising from transitions to the lower energy conduction band. A bandgap of 3.0 eV has been assigned by extrapolation of the low-energy band edge and an approximate energy diagram of the π manifold is proposed. The iodine-doped PMPAZ thin-film spectrum is dominated by the I3− signature and is accompanied by a pronounced vacuum-UV band edge while the π → π* multiplet is diminished and no longer discernible. Compensation with ammonia regenerates the conjugated azine manifold. © 1994, American Chemical Society. All rights reserved.

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Chemistry of Materials