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

In this work, two structurally different monoamines (trimethylamine (TMA) and N-methylpiperidine (N-MPip)) were 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 had superior electrochemical performance than N-MPip counterparts, while the mechanical properties were good and only slightly inferior to those of N-MPip. Therefore, TMA was 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 were 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) displayed the highest conductivity among all the investigated membranes aminated with polyamine-based mixtures. Moreover, they had comparable mechanical and electrochemical properties to those quaternized with TMA, while exhibiting a reduced water uptake. This article is protected by copyright. All rights reserved.