Effects of Structurally Different Tertiary Amines on the Properties of Quaternized Anionic Exchange Membranes Potentially Applicable for Water Electrolysis

Abstract

AbstractIn this work, two structurally different monoamines (trimethylamine [TMA] and N‐methylpiperidine [N‐MPip]) are used for the amination of a g‐VBC‐15 graft copolymer, obtained by the functionalization of a mechanically robust, commercially available styrene–butadiene block copolymer (SB) with vinylbenzyl chloride (VBC) via solution free‐radical polymerization. Results demonstrate that g‐VBC‐15‐based membranes quaternized with TMA have superior electrochemical performance than N‐MPip counterparts; while, the mechanical properties are good and only slightly inferior to those of N‐MPip. Therefore, TMA is the selected monoamine to be alternatively mixed with two polyamines (tetramethyl‐1,3‐propanediamine [TMPDA] and N,N,N’,N’’,N’’‐pentamethyldiethylenetriamine [PMDETA]) into different proportions, in order to modulate the average functionality of the amination mixture in terms of number of amine functional groups available for the quaternization reaction of the membranes. g‐VBC‐15‐based membranes derived therefrom are extensively characterized to assess their thermal, mechanical, and ex situ electrochemical properties. Results indicate that membranes quaternized with a TMA/PMDETA mixture (90:10 in mole) display the highest conductivity among all the investigated membranes aminated with polyamine‐based mixtures. Moreover, they have comparable mechanical and electrochemical properties to those quaternized with TMA, while exhibiting a reduced water uptake.