Sulfonated polytriazoles have drawn a great attention as high performance polymers and their good film forming ability. In the present study, a phosphorus containing new diazide monomer namely, bis-[4-(4 0 -aminophenoxy)phenyl] phenylphosphine was synthesized and accordingly, a series of phosphorus containing sulfonated polytriazoles (PTPBSH-XX) was synthesized by reacting equimolar amount of this diazide monomer (PAZ) in combination with another sulfonated diazide monomer (DSAZ) and a terminal bis-alkyne (BPALK) by the Cu (I) catalyzed azide-alkyne click polymerization. The polymers were characterized by nuclear magnetic resonance ( 1 H, 13 C, 31 P NMR) and Fourier transform infrared spectroscopic techniques. The sulfonic acid content of the copolymers also determined from the different integral values obtained from the 1 H NMR signals. The small-angle X-ray scattering results unfolded the wellseparated dispersion of the hydrophilic and hydrophobic domains of the polymers. As a whole, the copolymer membranes displayed sufficient thermal, mechanical, and oxidative stabilities high with high proton conductivity and low water uptake that are essential for proton exchange membrane applications. The copolymers exhibited oxidative stability in the range of 15-24 h and had proton conductivity values were found as high as 38-110 mS cm −1 at 80 C in completely hydrated condition. Among the all copolytriazoles, PTPBSH-90 (BPALK:DSAZ: PAZ = 100:90:10) having IEC W = 2.44 mequiv g −1 , showed proton conductivity as high as 119 mS cm −1 at 90 C with an activation energy of 10.40 kJ mol −1 for the proton conduction.

Polytriazoles are considered as an excellent high-performance polymer due to their outstanding set of properties. The current investigation reports the synthesis of a phosphorus-containing fluorinated diazide monomer, that is, bis[4-(4′-azidophenoxy)-3-trifluoromethyl phenyl] phenylphosphine oxide (PFAZ) and utilization of this compound to synthesize a set of trifluoromethyl groups and phosphine oxide containing sulfonated polytriazoles (PTPFBSH-XX). The copolymers with a different level of sulfonation (-XX = −60, −70, −80, −90) were prepared by the Cu(I) catalyst-assisted click reaction of equimolar amounts of a dialkyne (BPALK) and a mixture of diazides having one sulfonated diazide (DSAZ) and PFAZ. The polymers were further characterized by NMR ( 1 H, 13 C, 19 F, and 31 P) and FTIR spectroscopy. Freestanding membranes were attained from the dissolved copolymers solution in DMSO by standard solution casting route. The membranes showcased acceptable thermal and mechanical stabilities, excellent water management with a high proton conductivity, and outstanding oxidative stability. SAXS, TEM, AFM, and cross-sectional FE-SEM studies of the membranes indicated phase-separated morphology. The oxidative stabilities of the membranes ranged over 18 h. The polytriazole PTPFBSH-90 (PFAZ/DSAZ/BPALK = 10:90:100, where the degree of sulfonation is 90%) having a weight-based ion exchange capacity (IEC W ) of 2.39 mequiv g −1 exhibited a high proton conductivity of 142 mS cm −1 under hydrated conditions at 90 °C. Furthermore, PTPFBSH-XX polymer membranes displayed a comparable performance in microbial fuel cell as Nafion117. The chemical oxygen demand removal results indicated that the polymeric membranes could be sustainable in bioelectrochemical systems.

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A phosphaphenanthrene-based diazide monomer, 1,1-bis-(4-azidophenyl)-1-(6-oxido-6H-dibenz⟨c,e⟩⟨1,2⟩oxaphosphorin-6-yl) ethane (DPAZ), was synthesized via diazonium compound formation. DPAZ was used as one of the comonomers along with a sulfonated diazide to prepare a series of sulfonated polytriazoles (PTDPBSH-XX, where XX denotes the molar percentage of the sulfonated diazide in the diazide mixtures) through copper-induced click polymerization with the bisphenol-based dialkyne (BPALK). The products were analyzed using Fourier transform infrared (FTIR) and NMR techniques. Size exclusion chromatography (SEC) results indicated the formation of high molar mass products (weight average molecular weight as high as 74 900 g mol–1 with a polydispersity index (PDI) of 2.13). The polytriazoles showed high thermal stability, and the solution cast membranes from dimethyl sulfoxide (DMSO) were flexible and had good mechanical integrity. PTDPBSH-XX copolymers displayed high proton conductivity (141 and 152 mS cm–1 at 80 and 90 °C, respectively, for PTDPBSH-90 with a weight-based ion exchange capacity (IECW) of 2.46 mequiv g–1) with balanced water management and high oxidative stability (>16.5 h). The images of the cross-sectional membranes obtained from atomic force microscopy (AFM) and field emission scanning electron microscopy (FE-SEM) studies revealed hydrophilic–hydrophobic phase-segregated morphology. Besides, the microbial fuel cell performances of the membranes were comparable with that of Nafion 117.

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