Membrane properties of sulfonated polytriazoles with molecular branching

Abstract

The incorporation of branching units in the polymer is beneficial in improving many of the polymer properties. This article deals with the synthesis of branched sulfonic acid–based copolytriazoles (PTHPSH‐XX) to prepare freestanding membranes. The copolymers were synthesized by the click reaction of 1,4‐bis(prop‐2‐ynyloxy)benzene, 1,3,5 tris[2‐trifluoromethyl‐4(4‐azidophenyl) phenoxy]benzene (B3), and 4,4′‐diazido‐2,2′‐stilbene disulfonic acid disodium salt. The chemical constructions of the subsequent copolymers were established by Fourier‐transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy. The copolymers showed high thermal stability, low water absorption, and outstanding structural robustness in their hydrated state. The presence of branching segments (B3) in the copolymers contributed to improved peroxide radical resistance and proton conductivity (71–192 mS/cm measured at 90°C) in comparison with their linear analogs. In addition, the membranes exhibited reasonably good set of mechanical properties (TS = 71–53 MPa, YM = 2.76–2.33 GPa). The membranes exhibited phase‐separated morphology in their transmission electron microscope images with ionic domains of 20–160 nm.

Synthesis and characterization of sulfonated polytriazoles utilizing 1,4‐bis(4‐azido‐2‐(trifluoromethyl)phenoxy)benzene for the proton exchange membrane applications

“…In this context, 1,4‐bis(4‐azido‐2‐(trifluoromethyl)phenoxy)benzene (BATFB), a novel trifluoromethyl substituted diazide monomer, was synthesized. The molar mass of this monomer is relatively lower than many other previously reported –CF 3 containing diazide monomers and this resulted in higher IEC values of the copolymers based on this monomer 35,39 . This fluorinated diazide compound is used to control the resulting polymer's ion exchange capacity (IEC), which assisted in enhancing the proton conductivity and contracting the water uptake and swelling ratio of those polymer membranes.…”

“…Sharpless and co-workers develop a highly efficient and regioselective procedure of "click" cycloaddition reaction to synthesize novel triazole-linked PEM polymers with excellent yields. 39 In the last two decades, Cu(I)-induced "click" cycloaddition polymerization reaction between the azides and the terminal alkynes has been performed for the preparation of chemically stable and sufficient molecular weight 1,4-disubstituted 1,2,3-polytriazoles. 40 The N-heterocyclic triazole-linked polymers have high oxidative, chemical, and hydrolytic stability, due to the aromatic nature of the triazole rings.…”

“…43 Subsequently, several numbers of fluorinated sulfonated polytriazoles with different degrees of sulfonation (DS) were developed by Banerjee et al, which show sufficient proton conductivity and high mechanical, chemical, and thermal stabilities. [35][36][37][38][39]44,45 Based on the admirable performance of the fluorinated sulfonated polytriazoles, a new series of semifluorinated sulfonated polytriazoles with different DS has been synthesized and characterized. In this context, 1,4-bis(4-azido-2-(trifluoromethyl)phenoxy)benzene (BATFB), a novel trifluoromethyl substituted diazide monomer, was synthesized.…”

“…The molar mass of this monomer is relatively lower than many other previously reported -CF 3 containing diazide monomers and this resulted in higher IEC values of the copolymers based on this monomer. 35,39 This fluorinated diazide compound is used to control the resulting polymer's ion exchange capacity (IEC), which assisted in enhancing the proton conductivity and contracting the water uptake and swelling ratio of those polymer membranes. The presence of the bulky trifluoromethyl groups on BATFB enhances the phase separation between the hydrophobic and hydrophilic segments and additionally enhanced oxidative stability by avoiding peroxide assaults.…”

“…Also, incorporating the electron‐withdrawing trifluoromethyl groups (‐CF 3 ) into the sulfonated polymer backbone improved the overall oxidative and mechanical properties and diminished swelling 43 . Subsequently, several numbers of fluorinated sulfonated polytriazoles with different degrees of sulfonation (DS) were developed by Banerjee et al, which show sufficient proton conductivity and high mechanical, chemical, and thermal stabilities 35–39,44,45 …”