Synthesis and Characterization of Partially Renewable Oleic Acid-Based Ionomers for Proton Exchange Membranes

• Published in: Polymers Vol. 13; no. 1; p. 130
• Main Authors: Corona-García, Carlos, Onchi, Alejandro, Santiago, Arlette A, Martínez, Araceli, Pacheco-Catalán, Daniella Esperanza, Alfonso, Ismeli, Vargas, Joel
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI 30.12.2020; MDPI AG
• Subjects: long-chain polyamide; metathesis; oleic acid; proton exchange membrane; renewable ionomer; sulfonated polymer; long-chain polyamide; proton exchange membrane; sulfonated polymer; renewable ionomer; metathesis; oleic acid
• ISSN: 2073-4360; 2073-4360
• DOI: 10.3390/polym13010130

The future availability of synthetic polymers is compromised due to the continuous depletion of fossil reserves; thus, the quest for sustainable and eco-friendly specialty polymers is of the utmost importance to ensure our lifestyle. In this regard, this study reports on the use of oleic acid as a renewable source to develop new ionomers intended for proton exchange membranes. Firstly, the cross-metathesis of oleic acid was conducted to yield a renewable and unsaturated long-chain aliphatic dicarboxylic acid, which was further subjected to polycondensation reactions with two aromatic diamines, 4,4'-(hexafluoroisopropylidene)bis( -phenyleneoxy)dianiline and 4,4'-diamino-2,2'-stilbenedisulfonic acid, as comonomers for the synthesis of a series of partially renewable aromatic-aliphatic polyamides with an increasing degree of sulfonation (DS). The polymer chemical structures were confirmed by Fourier transform infrared (FTIR) and nuclear magnetic resonance ( H, C, and F NMR) spectroscopy, which revealed that the DS was effectively tailored by adjusting the feed molar ratio of the diamines. Next, we performed a study involving the ion exchange capacity, the water uptake, and the proton conductivity in membranes prepared from these partially renewable long-chain polyamides, along with a thorough characterization of the thermomechanical and physical properties. The highest value of the proton conductivity determined by electrochemical impedance spectroscopy (EIS) was found to be 1.55 mS cm at 30 °C after activation of the polymer membrane.