Conducting polymers (CPs) provide a class of processible, film forming semiconductors and metals. Electrical and optical properties of CPs, similar to those of metals and semiconductors, and the attractive properties associated with conventional polymers such as ease of synthesis and processing, has given these polymers a wide range of applications in the microelectronics industry, in biological field and also as humidity, chemical and mechanical sensors. The principal interest in the use of polymers lies in the scope for low cost manufacturing. Organic polymers offer several advantages over analogous inorganic semiconductors, the most important of which are the processability and the large surface film technology together with the possibility of tuning the polymer properties through a chemical design of the constituent units. In contrast, problems of environmental stability and the inability to process these into useful devices constitute the main drawbacks of organic materials. To set a material suitable for applications in various technological fields one has to improve the processability, mechanical strength and environmental stability of the polyheterocycles: one method adopted to do this is synthesizing the composites of conducting polymers within a matrix of insulating polymers. In this paper, the science of conducting polymers will be discussed. A review from literature on selected applications of organic devices based on conducting polythiophene and its composites will be discussed with a view to targeting the areas of future research in this topic.

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Polythiophene (PTh) -polyvinyl acetate (PVAc) composite fi lms were prepared by chemical oxidative polymerization with ZnCl 2 as oxidant, in methanol solvent at room temperature. In this study DC conductivity as a function of temperature was measured. An attempt has been made to investigate the effect of temperature and concentration of ZnCl 2 oxidant on the conductivity of polythiophene and polyvinyl acetate composite fi lms. For fi xed wt % of PVAc, the DC electrical conductivity initially increases with the molar concentration of ZnCl 2 which increases the rate of polymerization and then decreases with further increase in concentration of ZnCl 2 due to reduced segmental motion of the polymer. The Fourier transforms infrared (FTIR) spectra reveal that the structure remains the same throughout the series. The small shift in the observed peak frequencies is due to composition change of ZnCl 2 , but the overall trend of the IR spectra is the same. From the fi nger print region it is observed that the terminal branching is completely absent. The ionic transference number is calculated from the polarization current versus time plot. Ionic contribution is found to be dominant. The thermo gravimetry (TG) curves of the samples show single step degradation.