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We have investigated the properties of thin films of a substituted polypyrrole synthesized via the chemical oxidation of a chloroform solution of 5-acetamido-4,5,6,7-tetrahydro-2H-benzo[c]pyrrole. Repeated compressions of Langmuir films prepared by spreading a dilute chloroform/dimethyl sulfoxide solution 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 compression and decompression. An infrared spectroscopic investigation was carried out for KBr mixed pellets of the material and for Langmuir−Blodgett (LB) films obtained by depositing six monolayers of the polymer on ZnSe crystals. The presence of a broad bipolaron band both in the transmission and in the attenuated total reflection (ATR) spectra indicates that in its pristine form the polymer was already slightly doped, a hypothesis confirmed by preliminary two-probe measurements. To better understand the nature of the organization of the deposited films we performed a linear dichroism analysis of the polarized ATR spectra and found evidence that the polymeric chains are transferred in a helical manner along the surface of the substrate.

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We have investigated the photovoltaic response and measured the impedance of mixed Langmuir–Blodgett films of retinal derivatives and behenic acid along three perpendicular directions. The results indicate that the molecular dipoles in these samples are preferentially oriented in the direction perpendicular to the substrate. This microscopic arrangement is responsible for the observed anisotropy of both the dielectrical and photovoltaic properties of these thin organic films.