Preparation and Characterization of Conducting Chemo-sensitive Layers Based on Alkoxy-substituted polythiophenes

This study was aimed at improving the knowledge of the use of conducting polymers as sensing layers. Conducting chemo-sensitive layers obtained by the deposition of suspensions of chemically doped alkoxy-substituted polythiophenes, i.e. poly(3,3-dipentoxy-2,2-bithiophene) and poly[3,3-2-(2-ethoxy)ethoxy-2,2-bithiophene], were characterized by comparing the stability over time of resistance values during storage in both dry and laboratory environments, and by measuring the electric resistance variations following exposure to chemicals. Experimental data show that a good stability was obtained in all cases, although polymeric layers produced from two different batches of synthesis behaved differently. The behaviour of sensing layers in response to different concentrations, in nitrogen, of organic compounds of environmental and biomedical interest was monitored in terms of sensitivity, selectivity and reproducibility. The percentage variation in electrical resistance following exposure to organic vapours was found to vary linearly at low-medium concentrations. Differentiation and reliability of responses of several alkoxy-substituted thiophenes doped with different dopants and molar ratios are reported.