Conducting Polymers from Heterocyclic Compounds

Hu, Gang (1995). Conducting Polymers from Heterocyclic Compounds. PhD thesis The Open University.



The novel electroactive polymers poly(5,6-dimethylisothianaphthene) (PDMITN) and poly(4-methoxyisothianaphthene) (PMeOITN) have been synthesised. As with polyisothianaphthene (PITN), PDMITN can be obtained by both electrochemical and pure chemical oxidation from the monomers 5,6-dimethylisothianaphthene (DMITN) and 5,6-dimethyl-1,3-dihydroisothianaphthene (DMDHTTN). Using a nucleophilic electrolyte, tetrabutylammonium bromide (TBNBr), and dichloromethane the conductivity of PDMITN was as high as 100 Scm-1. The polymer film undergoes a high contrast colour change from blue in the neutral form to yellow/transparent in the oxidised form. PMeOITN, however, can only be prepared by electrochemical oxidation from the monomers 4-methoxyisothianaphthene and 4-methoxy-1,3-dihydroisothianaphthene when a non-nucleophilic electrolyte, tetraethyl ammonium tetrafluoroborate (TENBF), is used. PMeOITN is soluble in dichloromethane and chloroform, but, the polymer film does not undergo a strong colour change unlike PDMITN and PITN.

The properties of PDMITN and PMeOITN have been investigated using FT-IR, NMR, UV/Vis-near IR, X-ray powder diffraction and Cyclic voltammetry and compared with those of PITN.

The consumption of monomers and the formation of intermediates during electrochemical and chemical oxidation of the isothianaphthene derivatives were examined using cyclic voltammetry, time-resolved electronic absorption spectrometry and HPLC. The presence of methyl and methoxy groups does indeed affect the polymerisation process.

Silicon containing monomers including 1,1,3,4-tetramethyl-1-sila-3-cyclopentene (TMSCP), 1,1,3,4-tetramethylsilacyclopentadiene (TMSCPD) and 1,1 -dimethyl-2,3,4,5-tetraphenyl-1-silacyclopentadiene (TPSCP) have been successfully synthesised in good yield. Attempts to polymerise these silicon containing compounds have been carried out.

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