Synergy between the Assembly of Individual PEDOT Chains and Their Interaction with Light

Abstract

A new method for poly (3, 4-ethylenedioxythiophene) (PEDOT) synthesis based on acid-assisted polymerization is proposed, and the optical and structural properties of the obtained material are explored. Special attention is given to the effect of the polar Bronsted acid on the formation of oligomer/polymer chains and their ability to assemble into nanoobjects. By using 1H and 13C NMR spectroscopy (in the liquid and solid state), the formation of PEDOT in a neutral state was proven. Matrix-assisted laser desorption/ionization–time-of-flight, static light scattering, and dynamic light scattering spectroscopies were used to determine the M w and size of PEDOT nanoobjects. Moreover, we used density functional theory calculations to seek a correlation between the length of the PEDOT oligomer chain and the position of its lowest-energy absorption peak S1. All calculations were performed in concentrated formic acid and compared with calculations in the gas phase. In addition, we demonstrate a correlation between the photoluminescence (PL) from individual PEDOT chains and that from PEDOT chains assembled into nanoobjects. While individual PEDOT chains show four PL peaks, the assembled PEDOT nanoobjects show only one PL peak. Tuning the process of self-assembly for individual PEDOT chains is a promising way to control the properties of a polymer material.

Preparation of Smart Surfaces Based on PNaSS@PEDOT Microspheres: Testing of E. coli Detection

“…The microspheres were used as cores in the preparation of the PNaSS@PEDOT microsphere particles ( Scheme 2 ). The polymer film was obtained in the process of acid-assisted self-polymerization of the monomer (3,4-ethylenedioxythiophene, EDOT); the reaction was first described by our research group [ 44 , 45 ]. The synthesis can be summarized as follows: the prepared microspheres were dispersed in concentrated formic acid, and EDOT monomer was added to the dispersion.…”

“…The acid-assisted self-polymerization of the EDOT monomer without the formation of by-products was first revealed by our research group and studied in detail [ 44 ]. The analysis of high-resolution core-level S2p X-ray photoelectron spectra (XPS) confirmed that only polymers with reduced monomer units were formed during acid-assisted self-polymerization [ 44 ].…”

“…On the other hand, PEDOT has a peak at ~164 eV, which corresponds to the reduced sulfur atom in thiophene fragment. A small shoulder at ~168 eV was recorded for PEDOT (~6%); our previous studies have demonstrated that this peak corresponded to thiophene sulfur that lost electron density due to the formation of hydrogen bonds between the formic acid and thiophene unit [ 44 ]. The final PNaSS@PEDOT microsphere material shows both the peaks corresponding to reduced thiophene sulfur (~84 atomic%, the values were calculated from the intensities of both peaks) and the peak attributed to oxidized sulfur (~16%) from the sulfo groups of microspheres and/or the thiophene sulfur that has diminished electron density due to the formation of hydrogen bonds between the formic acid and thiophene rings ( Figure 2 ).…”

“…The main peak (PEDOT (100)) is positioned at 2Θ = 6.55°, which corresponds to 13.48 Å; the peak width is 1.974° [ 44 ]. Based on this value, we estimated the size of the ordered domain using the Scherrer equation.…”

“…The sensing layer obtained from PNaSS@PEDOT microspheres is stable and, more importantly, reproducible. Moreover, the new acid-assisted self-polymerization method for EDOT monomer is biologically friendly, and the final PEDOT shell is composed of the polymer in the reduced state [ 44 , 45 ], which makes the PNaSS@PEDOT microspheres suitable as an antifouling coating layer, as shown in Scheme 1 . On the one hand, this structure provides limited affinity of the surface towards bacteria; on the other hand, the reduced state facilitates internal conductivity by the presence of the core containing the sulfonate groups in each monomer unit.…”