Phosphorus‐Containing Fluoro‐Sulfonated Polytriazole Membranes with High Proton Conductivity: Understanding Microstructural and Thermomechanical Behaviors as a Function of Degree of Sulfonation

Abstract

AbstractThe current article describes the design and synthesis of a new series of phosphorus‐containing fluoro‐sulfonated polytriazoles through click polymerization. The synthesized copolytriazoles (PTPFDSH‐70 to 90) with different degrees of sulfonation (DS) from 70% to 90% are structurally interpreted by various spectroscopic techniques (1H, 13C, and FTIR). The high molecular weight (weight average molecular weight as high as 77 500 g mol−1 with polydispersity index of 2.29) polymers exhibits excellent mechanical (elongation at break up to 95%), thermal (10% decomposition temperature: 266–317 °C), and oxidative (>14.5 h) stability. The PTPFDSH‐70 to 90 possess outstanding water‐holding ability in hydrated conditions (swelling ratio [in‐plane]: 6.2–7.3% at 80 °C). The microstructural alterations by their thermal relaxations and transitions with increasing DS in the polymers have been thoroughly investigated by dynamic mechanical analysis. The atomic force microscopy and transmission electron microscope images of the PTPFDSH‐70 to 90 polymer membranes demonstrated the phase segregated interconnected ionic cluster‐like morphology between hydrophilic and hydrophobic domains. The PTPFDSH‐90 (DEB:PFAZ:DSAZ = 100:10:90) polymer membrane displays the proton conductivity (176 and 190 ms cm−1 at 80 and 90 °C, respectively) higher than Nafion117 under similar test conditions.