Ionic π‐Conjugated Polyelectrolytes by Catalyst Free Polymerization of Bis(pyridyl)acetylenes and Bis[(pyridyl)ethynyl]benzenes

Abstract

The spontaneous, catalyst free polymerization of four monomers of the bis(pyridyl)acetylene and bis[(pyridyl)ethynyl]benzene types containing either 2-pyridyl or 4-pyridyl groups via activation with benzyl bromide leads to ionic π-conjugated polyacetylene-type polyelectrolytes (CPEs). All polymers are characterized by means of NMR, IR, UV/vis and photoluminescence spectroscopies, thermogravimetric analysis (TGA) and matrix assisted laser desorption/ ionization time of fl ight mass spectrometry (MALDI-TOF MS). The position of the pyridyl groups in the monomer infl uences the degree of quaternization and the extent of conjugation of CPEs. Monomers with 4-pyridyl groups provide CPEs with a low extent of quaternization [N + /(N + + N) = 0.27-0.34] and high extent of conjugation. On the other hand, the CPEs derived from 2-pyridyl-containing monomers are highly quaternized [N + /(N + + N) = 0.77-1.00], however, possess lower conjugation of the main chains. The mechanism assuming quaternization and polymerization as competitive reactions is proposed to explain the difference in the extent of quaternization of CPEs. Prepared CPEs i) are well soluble in polar solvents, e.g., water, methanol, dimethyl sulfoxide, and dimethylformamide, ii) exhibit photoluminescence (emission in the violet to yellow region), and iii) possess high thermal stability. materials with a wide variety of applications, [1][2][3][4][5][6][7][8] including light-emitting diodes (LEDs), [ 9 ] light-emitting electrochemical cells (LECs), [ 10 ] plastic lasers, [ 11 ] solar cells, [ 12 ] fi eld-effect transistors (FETs) [ 13 ] and porous materials. [ 14,15 ] The π-conjugated polyelectrolytes (CPEs) represent a special subclass of CPs. [ 16 ] The CPE polymers comprise π-conjugated main chains and ionic and/or ionizable groups. Unlike the majority of neutral CPs, CPEs additionally exhibit i) solubility in polar solvents as water, aqueous solutions, alcohols, and others environmentally friendly solvents, [17][18][19] ii) amphiphilic nature, which gives CPE macromolecules capability of self-assembling in solutions and ability to interact specifi cally with particular species under measurable optical and/or electrical responses, and iii) simultaneous electronic and ionic conductivity [ 20 ] reducing the electron-injection barrier Emission spectra 400 450 500 550 600 650 Wavelength (nm) Br N N N N N N N N N N Br Br Br Br Br NO CATALYST poly(4PD)

Ionic π-Conjugated Polymer Networks by Catalyst-Free Polymerization, Photoluminescence and Gas Sorption Behavior

“…The overall higher degree of quaternization of reported networks, compared to the quaternization of their linear counterparts prepared via quaternization polymerization of the same monomers activated with (monofunctional) benzyl bromide reported previously, is presumably caused by the bifunctional character of 1,4‐bis(bromomethyl)benzene applied as a QA in the synthesis of networks. The molecules of nonquaternized monomer which diffuse to the vicinity of growing polymer chains come, in fact, to the part of the reaction system with a high concentration of BrCH 2  groups (pendant groups of growing polymer chains).…”

“…All the monomers applied in this study except for 2PM exhibit photoluminescence in the UV region (emission maxima at 350–360 nm) . On the contrary, all the polymer networks emit in visible or visible/near IR region (see Figure ).…”

“…Probably the most important structural difference is evident from a comparison of units M1 and M2 in Scheme these units differ in the number of the preserved ethynyl groups. It should be noted that the symmetrical shoulder‐free bands (2222 cm −1 ) due to the CC bond stretching vibration were present in the IR spectra of 2PD and 4PD monomers …”

“…Digits in the codes specify the positional isomerism of the pyridyl substituents (2P— ortho ‐positioned pyridyl groups, 4P— para ‐positioned pyridyl groups), M—stands for the monoacetylenic character of the monomer, D—stands for the diacetylenic character of the monomer. The synthesis of the monomers is described in the article …”

“…Details on the preparation and spectral characterization of monomers, 1,2‐bis(2‐pyridyl)acetylene (2PM), 1,2‐bis(4‐pyridyl)acetylene (4PM), 1,4‐bis[(2‐pyridyl)ethynyl]benzene (2PD), and 1,4‐bis[(4‐pyridyl)ethynyl]benzene (4PD), are presented in the article . The spectra of the monomers ( 1 H NMR, 13 C NMR, IR) were in a good agreement with the spectra available in the literature …”