The authors study the photophys. properties of the pyridine-based polymers poly(p-pyridyl vinylene) (PPyV) and poly(p-pyridine) (PPy). The primary photoexcitations in the pyridine-based polymers are singlet excitons. The authors observe direct intersystem crossing (ISC) on picosecond time scales with the vol. d. of triplet excitons varying with the sample morphol. (film or powder). These effects are demonstrated clearly by examg. the millisecond photoinduced absorption characteristics of powder and film forms of PPyV. The pyridine-based polymers were shown to be promising candidates for polymer light-emitting devices, both conventional diode device and sym. configured ac light-emitting (SCALE) device. Here the authors examine the role of insulating layers and their interfaces with the emitting layer and electrodes in the SCALE device operation, with emphasis on the central role of the polymer-polymer interfaces. [on SciFinder(R)]