Low-pressure-induced conformational transition in doped polypyrrole: optical and IR spectra

A pressure dependence of the optical absorption spectra of BF−4-doped polypyrrole has been observed at pressures below atmospheric pressure. The two absorption bands at photon energies of 1·2 and 3·0 eV depend on the pressure: a decrease in the high-energy absorption is accompanied by an increase in the low-energy absorption and its shift towards lower energies. The Fourier transformation infrared reflection spectra also depend on the pressure in this region of pressures. The results are interpreted as a pressure-induced conformational transition of the polypyrrole chain. © 1998 John Wiley & Sons, Ltd.