Trifluoromethyl functionalized sulfonated polytriazoles from diphenylphosphine oxide-based dialkyne via click polymerization: Effect of high content of phosphorus on the proton exchange membrane properties

Abstract

A new diphenylphosphine oxide based dialkyne, [2,5-bis(prop-2-yn-1-yloxy)phenyl]diphenylphosphine oxide (POALK) has been prepared under mild reaction conditions. Using this POALK monomer, a new-fangled fluorinated sulfonated polytriazoles (PTPPS-70 to -90 and PTPS-100) with a high content of phosphine oxide moieties were prepared via the click polymerizations with other two comonomers [sulfonated diazide (DSAZ) and non-sulfonated phosphorus containing diazide (PFAZ)]. FT-IR and NMR (1H, 13C, and 31P) spectroscopic techniques were used for the structural elucidations of the synthesized monomer and polymers. The high molecular weight (weight average molecular weight: 59,600–75,800 g mol−1 and PDI: 1.65–2.20) sulfonated polymers demonstrated exceptional thermal, mechanical and thermomechanical steadiness. The higher content of phosphorus (3.83–4.54%) in the copolymers (IECW: 1.58–2.16 meq g−1) has occasioned excellent harmony among the water uptakes (WU), swelling ratios (SR), and proton conductivity (σ). The coexistence of triarylphosphine oxide units (both in the dialkyne and diazide monomers) in the polymers slowed down the peroxide radical attacks. The observed interconnected ionic nanochannels in the phase segregated morphology in AFM and TEM images of sulfonated polytriazoles (PTPPS-70 to -90 and PTPS-100) facilitate the proton transportation that resulted in high proton conductivity.