INFRARED SPECTRAL HOLE-BURNING OF POLYMERS - A PROBE OF LOCAL-STRUCTURE

Infrared hole-burning studies of the ionic polymers poly(ammonium styr enesulfonate) and ammonium Nafion are reported. The ammonium groups ar e doped with a few percent of deuterium, and the irradiation is in the N-D stretching bands. Both polymers show only broad spectral absorpti on bands, but the narrow spectral holes reveal details of the ammonium group interactions with their surroundings. The results are interpret ed by comparison with the hole burning of the model compounds ammonium tosylate and ammonium triflate. Characteristic behavior of the holes shows that some of the local conformations of the models persist in th e polymers. Particularly unusual are the changes of hole depth with ti me: for the Nafion, some holes decay for a period of time, then grow, and then continue to decay--a behavior also observed in the model trif late.