Temperature dependent structural stability of ladder type poly(p-phenylenes)

We report on temperature (104K - 575K) dependent Raman investigations of tw o ladder type poly(paraphenylenes), LPPP and mLPPP, This temperature range is important for applications in light emitting devices. A usual weak softe ning with increasing temperature of inter-and intra-ring line positions ind icate rather stable intra-molecular structure. A non reversible background above 555K demonstrates increasing degeneration processes, Additional a str iking behavior of some line intensities are found which seem to be related to long distance rearrangements due to inter-chain coupling.