Thin films of a new polar substituted polypyrrole

We have investigated the properties of thin films of a substituted polypyrr ole synthesized via the chemical oxidation of a chloroform solution of 5-ac etamido-4,5,6,7-tetrahydro-2H-benzo[c]pyrrole. Repeated compressions of Lan gmuir films prepared by spreading a dilute chloroform/dimethyl sulfoxide so lution of the polymer at an air-water interface have established their long -term stability as floating monolayers. Hysteresis experiments and surface potential measurements have indicated that while the stiff condensed layer changes its structure upon the first compression, the size and distribution of floating domains remain invariant under subsequent cycles of compressio n and decompression. An infrared spectroscopic investigation was carried ou t for KBr mixed pellets of the material and for Langmuir-Blodgett (LB) film s obtained by depositing six monolayers of the polymer on ZnSe crystals. Th e presence of a broad bipolaron band both in the transmission and in the at tenuated total reflection (ATR) spectra indicates that in its pristine form the polymer was already slightly doped, a hypothesis confirmed by prelimin ary two-probe measurements. To better understand the nature of the organiza tion of the deposited films we performed a linear dichroism analysis of the polarized ATR spectra and found evidence that the polymeric chains are tra nsferred in a helical manner along the surface of the substrate.