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

Abstract

Four monomers of the bis(pyridyl)acetylene and bis[(pyridyl)ethynyl]benzene types containing either 2-pyridyl or 4-pyridyl groups are polymerized into respective networks of the conjugated polyelectrolyte (CPE) type by catalyst-free polymerization via activation with 1,4-bis(bromomethyl)benzene as quaternization agent (QA). Prepared CPE networks are characterized by elemental analysis (EA), TGA analysis, 13C cross-polarization magic-angle spinning NMR, IR, UV/vis, and photoluminescence spectroscopies. Highly cross-linked network structure containing both π-conjugated polyacetylene type chains and ionic alternating type chains is proposed. According to EA analysis, the mole ratio of units derived from monomer molecules and QA molecules is close to unity in all prepared networks. The CPE networks based on 4-pyridyl monomers exhibit strong photoluminescence in the visible region after irradiation with light of wavelength of 378 nm. Prepared CPE networks also show moderate efficiency in CO2 sorption up to 13.6 cm3 g−1 (STP) and exceptionally high ethanol vapor capture efficiency up to 24.5 wt% (293 K). The specific interactions of ionic network and adsorbed molecules and also temporary pores formation are assumed to play important role in sorption processes.