Synthesis And Application Of Polythiophene Derivatives With Cationic Side Chain

Cationic polythiophene derivatives have been widely used in chemical sensors, molecularswitches and biological probes due to their unique optical, electrical and processable properties.Here, three new monomers3-(1-methyl-4-piperidinemethylene)thiophene (MPMT),3-(1,1’-dimethyl-4-piperidinemethylene]thiophene methyl sulfate (DPMTMS) and3-(1-methyl-1’-ethyl-4-piperidinemethylene)thiophene bromide (MEPMT-Br) were obtained from3-methylthiophene as starting material and then through NBS bromination, Witting-Hornerreaction and quaternary ammoniation. The structures of these monomers were characterizedwith1H NMR and FIIR. Then three monomers were polymerized by ferric chloride oxidativepolymerization to obtain three new polythiophene derivatives including poly(3-(1-methyl-4-piperidinemethylene)thiophene)(PMPMT), poly(3-(1,1’-dimethyl-4-piperidinemethylene)thiophene-2,5-diyl chloride)(PDPMT-Cl) and poly(3-(1-methyl-1’-ethyl-4-piperidinemethyl-ene) thiophene-2,5-diyl bromide)(PMEPMT-Br). The structures of these polymers werecharacterized using1H NMR, FTIR and GPC, and their optical and electrical properties werestudied by UV-vis, FL, TG and CV methods.Due to their favorable optical properties, water-soluble polythiophene derivativesPDPMT-Cl and PMEPMT-Br were applied as colorimetric and fluorometric probes for thedetection of common ions, surfactant and biological substances. The results showed thatPDPMT-Cl was specific to detect iodide ion and anionic surfactant with colorimetric detectionlimit of10-5M and10-6M, respectively, and the fluorescent detection limit to iodine ion andanionic surfactant could reach to10-8M and10-9M, respectively. PMEPMT-Br only has betterspecificity to anionic surfactant detection with colorimetric and fluorescent detection limit of10-6M and10-9M, respectively.