Synthesis, characterization and polymerization of 3,4-ethylenedioxythiophens substituted at ethylene bridge

Abstract

Various routes to synthesis of EDOT substituted at ethylene bridge and other related derivatives have been attempted. Synthesis of new diethyl 3,4-dialkoxythiophene-2,5-dicarboxylate derivatives using double Williamson etherifications of the corresponding alkyl halides yielded the desired thiophene dicarboxylate precursors in range of yields. Decarboxylation obtained a new potential monomer (Vinyl-EDOT). Halogenation of various thiophene derivatives with N-bromosuccinimide (NBS) or N-chlorosuccinimide (NCS) have been accomplished in excellent yields (80-99%). Transetherification of 3,4-dimethoxy- thiophene with trans-1,2-cyclohexanediol to obtain 3,4-cyclohexylenedioxy- thiophene (CDOT) in good yield (86%). This monomer was subjected to oxidative polymerization to give poly(3,4-cyclohexylenedioxythiophene) (PCDOT) in 69%. 2,5-Dibromo-3,4-cyclohexylenedioxythiophene (DBCDOT) could be polymerized in solid state which also gave the polymer PCDOT. Characterizations of the resulting polymer were performed by NMR, FT-IR, SEM, UV-Vis, XRD, MALDI-TOF MS, TGA, DSC and Four-point-probe conductometer. Solid-state polymerized PCDOT heated at 120 ºC for 24 hours and stored at room temperature for 14 days gave the best value of conductivity up to 131 S/cm.