Synthesis of processible poly(3,4-dialkoxy thiophene)

Abstract

The research studied the substituents modification by ether exchange from ethylene dioxy bridges on EDOT, DBrEDOT and PEDOT to other dialkoxy derivatives followed by the bromination and polymerization either through solid state polymerization (SSP) or oxidative coupling processes. The products from the modifications: 3,4-dimethoxythiophene (DMT), 3,4-dibutoxythiophene (DBT), 2,5-dibromo-3,4-dimethosythiophene (DBrDMT) and 2,5-dibromo-3,4-dibutoxythiophene (DBrDBT) were obtained in 8.5, 42.5, 18.7 and 10.2% yield respectively. The best acid catalyst in the ether exchange was p-toluenesulfonic acid (PTSA). The brominations with NBS gave 2,5-dibromo-3,4-ethylenedioxythiophene (DBrEDOT), 2,5-dibromo-3,4-dibutoxythiophene (DBrDBT), 2,5-dibromo-3- methoxythiophene (DBrMT) and 2,5- dibromothiophene-3-carboxylic acid in 65.7, 76.1, 32.6, 26.3 and 30.1% yield respectively. Oxidative coupling polymerizations yielded PEDOT, PDMT, PDBT and PMT in 92.3, 61.8, 62.2 and 77.0% yield respectively. Solid state polymerization was achieved only with 2,5-dibromo-3,4-ethylenedioxythiophene giving PEDOT. The highest conductivity of iodine doped polymer belongs to DEPOT synthesized through SSP process.