Functionalized highly electron-rich redox-active electropolymerized 3,4-propylenedioxythiophenes as precursors and targets for bioelectronics and supercapacitors

Abstract

In order to combine capacitive properties with processability, e.g. solubility in organic solvents, poly(3,4-propylenedioxythiophene) derivatives containing different functional groups like oxyphenyl methanol (–OPhCH₂OH), oxybenzyl (–OBz), bromide (–Br) and tosyl (–OTs) were synthesized and electropolymerized as thin films from acetonitrile (ACN) using Et₄NBF₄ as an electrolyte. Multifunctionality in the substitution pattern of the polymer exhibits a similar trend between monomer oxidation potentials and specific capacitance (C_sp) vs. crystal size. The presence of π–π stacking interactions in the polymer structures plays an important role in building the crystal structures. The same order of flat band potential and C_sp values are observed for –OBz < –Br < –OTs < –OPhCH₂OH substitutions. The structures of PProDOT–OBz and PProDOT–OPhCH₂OH resemble each other much more than those of PProDOT–Br and PProDOT–OTs. Impedance measurements were conducted at different applied biases in order to define a Mott–Schottky analysis revealing the dependence of the semiconducting properties on the type of substituent present in the PProDOT derivative.