A series of conjugated cationic polymers, differentiated only by their accompanying counter-anions, was prepd. and characterized. The choice of counter-anion (CA) was found to drastically impact the soly. of the polymers and their optical properties in soln. and in the solid state. Fluorescent polymer thin films were found to be instantaneously quenched by volatile amines in the gas phase at low ppm concns., and a mini-array with CAs as variable elements was found to be able to differentiate amines with good fidelity. [on SciFinder(R)]