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