Phosphonium‐based polyelectrolyte networks with high thermal stability,high alkaline stability,and high surface areas

Phosphonium‐containing polyelectrolyte networks (PENs) ( P1 – P4 ) were prepared by cyclotrimerization of bis(4‐acetylphenyl)diphenylphosphonium bromide ( M1 ) and 1,4‐diacetylbenzene ( M2 ) with p‐toluene sulfonic acid in various M1:M2 ratios (1,0, 1:1, 1:2, and 1:4). The relative abundance of the PAr₄⁺ units in each PEN was demonstrated to influence thermal stability, alkaline stability, water uptake, surface area, and CO₂ uptake in predictable ways. Impressively, PENs with NTf₂^? counterions (Tf = CF₃SO₃) did not exhibit 5% mass loss until heating above 400 °C. Alkaline stability, tested by challenging a PEN with 6 M NaOH(aq) at 65 °C for 120 h, increased with increasing PAr₄⁺ content, which reflected the enhanced reactivity of the HO^? anion in more hydrophobic materials (i.e., PENs with lower M1:M2 ratios). The specific surface areas estimated by Brunauer‐Emmett‐Teller (BET) analysis for these PENs were above 60 m²/g under N₂ and nearly 90 m²/g under CO₂. Notably, P3 (in which 33% of monomers comprise a phosphonium moiety) exhibited a CO₂ uptake affinity of one CO₂ molecule adsorbed for every phosphonium site. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 598–604