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Effect of block composition on the morphology, hydration, and transport properties of sulfonated PS‐ b ‐PEGPEM‐ b ‐PS
Author(s) -
PérezPérez Maritza,
Suleiman David
Publication year - 2016
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.44343
Subject(s) - membrane , polymer chemistry , nafion , copolymer , atom transfer radical polymerization , chemical engineering , polymer , polymerization , materials science , methanol , proton exchange membrane fuel cell , ionic conductivity , proton transport , ionic bonding , chemistry , electrolyte , organic chemistry , ion , composite material , electrode , biochemistry , engineering , electrochemistry
This work discusses the effect of block composition on the properties of proton conducting polymer membranes. A homopolymer and two block copolymers were synthesized using atom transfer radical polymerization. The homopolymer poly(ethylene glycol phenyl ether methacrylate) (PEGPEM) was used as a bifunctional macroinitiator. Polystyrene (PS), was added to both sides of PEGPEM (A) with two different percentages of PS (B) (i.e., 18 and 31%). These copolymers, BAB 18, BAB 31 and the homopolymer A, were completely sulfonated (SA, SBAB 18 and SBAB 31). The resulting polymers produced different water absorption values and transport properties for direct methanol fuel cell (DMFC) applications. The nanostructure and morphology of the casted membranes were studied using small‐angle X‐ray scattering and atomic force microscopy. The results revealed that all six membranes exhibited a disordered phase‐segregated morphology, which changed on sulfonation into small‐interconnected ionic domains. Normalized DMFC selectivities (proton conductivity over methanol permeability divided by the respective values for Nafion ® ) were calculated and ranged from 1.16 (SBAB 31) to 15.30 (BAB 18), indicating that the performance of these materials can be comparable or better than Nafion ® . Transport property results also suggest that chemistry (block nature and composition), morphology and water content play a critical role in the transport mechanism of protons and methanol. For example, the percentage of B in BAB 18 provides shorter interstitial ionic distances and sufficient water content to produce high proton conductivity, while maintaining low methanol permeability in a multi‐ionic proton exchange membrane. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133 , 44343.