Electronic Spectroscopy of Poly(propylmethylazine)
Bradford C. Sherman, William B. Euler, Chemistry of Materials, 1994, 6, 899 – 906
Abstract
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 groups allows for limited solubility in some organic solvents but does not affect the approximate C2h symmetry of the conjugated π backbone indicative of a 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.