The preparation and application of a ROMP-type epoxy-functionalized norbornene copolymer and its hybrid alkaline anion exchange membranes

Abstract

A series of ROMP-type epoxy-functionalized norbornene copolymers named rP(BN/MGENB)-x, with different MGENB content, were synthesized by copolymerization of 5-norbornene-2-methylene butyl ether (BN) and 5-norbornene-2-epoxypropyl ether (MGENB) via ring-opening metathesis polymerization. The obtained rP(BN/MGENB)-49.2 showed the best molecular weight and processability performance for hybrid alkaline anion exchange membrane preparation. Based on this, cross-linked copolymer/silica hybrid alkaline anion exchange membranes, QrP(BN/MGENB-SiO₂-y) (y = 10, 20, 30 and 40 wt% TSPCA), were prepared by chemical reaction with N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride (TSPCA) and glutaric dialdehyde (GA). The effects of the TSPCA compositions on the mechanical properties, morphology, methanol resistance permeability, alkaline resistance stability, and ionic conductivity of the hybrid alkaline QrP(BN/MGENB-SiO₂-y) were investigated. QrP(BN/MGENB-SiO₂-10) exhibited the best comprehensive properties and ionic conductivity of all of the hybrid membranes. The ionic conductivity increased obviously with a rise in temperature, and values of 9.7 × 10⁻³ S cm⁻¹ at 30 °C and 41 × 10⁻³ S cm⁻¹ at 80 °C were obtained. A membrane electrode assembly (MEA) fabricated using QrP(BN/MGENB-SiO₂-10) was also tested in a direct methanol fuel cell, and a maximum open circuit voltage (OCV) of 0.95 V and a current density of 96.7 mW cm⁻² at a peak power density of 42.6 mW cm⁻² at 80 °C were achieved.