Related Experiment Video
Updated: Jun 2, 2026

Ion-Exchange Membranes for the Fabrication of Reverse Electrodialysis Device
Published on: July 20, 2021
Synthesis and evaluation of novel proton exchange membranes containing the semisquaric Acid group
Ken Yoshimura1, Lanny S Liebeskind
1Sumitomo Chemical Co., Ltd., Tsukuba Research Laboratory, 6 Kitahara, Tsukuba, Ibaraki, 300-3294, Japan. yoshimurak2@sc.sumitomo-chem.co.jp.
Abstract:
We focus our attention here on semisquaric acid, which is known to show high acidity, as a new proton dissociating group for proton exchange membranes (PEMs). The introduction of a squaric acid group into aromatic polymers was conducted by the reaction of lithiated aromatic polymers and diisopropoxy squarate, followed by treatment with hydrochloric acid. A resulting polyphenylsulfone membrane with the squaric acid group introduced (PPSf-SQ, IEC = 4.1 meq·g(-1) ) showed proton conductivity of 1.0 × 10(-1) S·cm(-1) at 80 °C under 95% relative humidity, which indicates that the semisquaric acid has the potential to become an alternative proton-conducting group for PEMs.
Related Concept Videos
Ion Exchange
Potentiometry: Membrane Electrodes
Diazonium Group Substitution: –OH and –H
Alkylation of β-Diester Enolates: Malonic Ester Synthesis
Titration in Nonaqueous Solvents
Acid Halides to Carboxylic Acids: Hydrolysis
As shown below, the mechanism involves a nucleophilic attack by water at the carbonyl carbon to form a tetrahedral intermediate. This is followed by the reformation of the carbon–oxygen π bond along with the departure of a halide ion. A final proton transfer step yields carboxylic acid...

