The synthesis of 3-octadecyl- and 3-docosylpyrrole, their polymerisation and incorporation into novel composite gas sensitive resistors

3-Octadecylpyrrole and the novel 3-docosylpyrrole were synthesised in high yields. These monomers were polymerised with various oxidising agents to produce a range of 3-octadecylpolypyrroles and 3-docosylpolypyrroles with different counter-ions. These polymers were soluble in chloroform and were readily coated onto microporous poly(vinylidene fluoride) membranes. Novel 3-alkylpolypyrrole--tin(IV) oxide composites were also produced by adding finely ground tin(IV) oxide to a solution of the 3-alkylpolypyrrole in chloroform and drop-coating the resulting mixture onto alumina substrates or poly(vinylidene fluoride) membranes. The resulting 3-alkylpolypyrrole based materials were tested for their gas sensitivity towards a number of classes of volatile organic compounds (VOCs). The 3-alkylpolypyrrole-tin(IV) oxide composites were found to exhibit enhanced sensitivity and differing selectivities to VOCs when compared to tin(IV) oxide or the 3-alkylpolypyrrole alone. Previously, conducting polymers exhibited little response to non-polar VOCs, in contrast 3-octadecylpolypyrrole-nitrate-tin(IV) oxide composite sensors were particularly sensitive to hydrocarbons and could detect butane and propane at concentrations well below their lower limit of explosion (LLE) (C) 2002 Elsevier Science B.V. All rights reserved.