Photoexcitation of poly( p -phenylene sulfoxide): signatures of triplet excitons

Near steady-state photoinduced absorption spectroscopy has been used for the initial study of millisecond photoexcitations in poly(p-phenylene sulfoxide) (PPSx). A photoinduced absorption (PA) band at ∼2.3 eV is observed. We conclude, based on the transition energy, and frequency and intensity dependence studies of this band, that this PA feature is associated with the formation of triplet excitons in PPSx. The PA spectrum of PPSx is compared with PA spectra previously reported for the leucoemeraldine base (LEB) form of polyaniline and poly(p-phenylene sulfide) (PPS). Ring-torsional polarons were identified as the dominant excitations in LEB and PPS. We suggest that the sulfoxide unit is one factor inhibiting the production of polarons in PPSx.