Abstract
In this work we report the synthesis of poly(vinylbenzylchloride-co-hexene) copolymer grafted with N,N-dimethylhexylammonium groups to study the effect of an aliphatic backbone without ether linkage on the ionomer properties. The copolymerization was achieved by the Ziegler–Natta method, employing the complex ZrCl4 (THF)2 as a catalyst. A certain degree of crosslinking with N,N,N′,N′-tetramethylethylenediamine (TEMED) was introduced with the aim of avoiding excessive swelling in water. The resulting anion exchange polymers were characterized by 1H-NMR, FTIR, TGA, and ion exchange capacity (IEC) measurements. The ionomers showed good alkaline stability; after 72 h of treatment in 2 M KOH at 80 °C the remaining IEC of 76% confirms that ionomers without ether bonds are less sensitive to a SN2 attack and suggests the possibility of their use as a binder in a fuel cell electrode formulation. The ionomers were also blended with polyvinyl alcohol (PVA) and crosslinked with glutaraldehyde. The water uptake of the blend membranes was around 110% at 25 °C. The ionic conductivity at 25 °C in the OH− form was 29.5 mS/cm.
Highlights
Anion exchange membranes (AEMs) are ion conducting materials used in several applications like anion exchange membrane fuel cells (AEMFCs) [1,2,3,4], water electrolysers [5], water treatments, and redox flow batteries [6,7]
In this study we focus on the backbone, in particular on the study of how the absence of ether bonds in the polymer matrix improves the chemical stability of anion exchange ionomers, synthesizing the copolymer poly(VBCl-co-hexene)
We aimed in this work: (i) to synthesize the new copolymer poly(VBCl-co-hexene) with no ether linkage looking for an increased stability in strong alkaline conditions, (ii) to obtain a high ionic conductivity because of the introduction of long spacer chains into the backbone and with the introduction of ammonium groups on long side chains, (iii) to obtain a blend membrane of poly(VBCl-co-hexene) and polyvinyl alcohol (PVA), presenting a plastic behavior similar to Nafion® due to the use of a flexible aliphatic backbone in both polymers
Summary
Anion exchange membranes (AEMs) are ion conducting materials used in several applications like anion exchange membrane fuel cells (AEMFCs) [1,2,3,4], water electrolysers [5], water treatments, and redox flow batteries [6,7]. In this study we focus on the backbone, in particular on the study of how the absence of ether bonds in the polymer matrix improves the chemical stability of anion exchange ionomers, synthesizing the copolymer poly(VBCl-co-hexene). We aimed in this work: (i) to synthesize the new copolymer poly(VBCl-co-hexene) with no ether linkage looking for an increased stability in strong alkaline conditions, (ii) to obtain a high ionic conductivity because of the introduction of long spacer chains into the backbone and with the introduction of ammonium groups on long side chains, (iii) to obtain a blend membrane of poly(VBCl-co-hexene) and polyvinyl alcohol (PVA), presenting a plastic behavior similar to Nafion® due to the use of a flexible aliphatic backbone in both polymers. One of the most accepted mechanisms for the Ziegler–Natta polymerization reaction One owf athseesmtaobsltisahcecdepbtyedComsseecehainni1s9m64s.fTohrethaectZZiviieagtiloenr–oNf athtteacpaotallyymsteirsizreaptioornterdeainctFioignure 2a was eessttaabblli[is4sh5he]e.ddbbyyCCoosseseeinin1916946.4T. hTehaecaticvtaivtiaotnioonf othfethceatcaalytasltyistreisporerpteodrtiendFignuFrieg2uare[425a]. [45]
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