Abstract
The optimization of fuel cell materials, particularly polymer membranes, for PEMFC has driven the development of methods and alternatives to achieve systems with more adequate properties to this application. The sulfonation of poly (styrene-co-allyl alcohol) (PSAA), using sulfonating agent:styrene ratios of 2:1, 1:1, 1:2, 1:4, 1:6, 1:8 and 1:10, was previously performed to obtain proton conductive polymer membranes. Most of those membranes exhibited solubility in water with increasing temperature and showed conductivity of approximately 10-5 S cm-1. In order to optimize the PSAA properties, especially decreasing its solubility, semi-IPN (SIPN) membranes are proposed in the present study. These membranes were obtained from the diglycidyl ether of bisphenol A (DGEBA), curing reactions in presence of DDS (4,4-diaminodiphenyl sulfone) and PSAA. Different DGEBA/PSAA weight ratios were employed, varying the PSAA concentration between 9 and 50% and keeping the mass ratio of DGEBA:DDS as 1:1. The samples were characterized by FTIR and by electrochemical impedance spectroscopy. Unperturbed bands of PSAA were observed in the FTIR spectra of membranes, suggesting that chemical integrity of the polymer is maintained during the synthesis. In particular, bands involving C-C stretching (1450 cm-1), C=C (aromatic, ~ 3030 cm-1) and C-H (2818 and 2928 cm-1) were observed, unchanged after the synthesis. The disappearance or reduction of the intensity of the band at 916 cm-1, attributed to the DGEBA epoxy ring, is evidenced for all samples, indicating the epoxy ring opening and the DGEBA crosslinking. Conductivity of H3PO4 doped membranes increases with temperature, reaching 10-4 S cm-1.
Highlights
Renewable energy sources are currently among theIn order to allow the commercialization of fuel cells (FC) in a most active research areas due to the global climate large scale, a significant cost reduction must be achieved, T changes and their consequences
Semi-interpenetrating polymer network (SIPN) membranes based on the diglycidyl ether of bisphenol-A (DGEBA) crosslinked with 4,4’diaminodiphenyl-sulphone (DDS) and poly(styreneco-allyl alcohol) were obtained and characterized by FTIR, electrochemical impedance spectroscopy and scanning electronic microscopy, in a prospective study for its future application as proton conductive membrane in PEMFC
The surface continuity and compactness observed for the DGEBA/poly(styrene-co-allyl alcohol) (PSAA) Semi-IPN membranes is key for its application in FC devices, since fuel crossover must be avoided and membrane porosity is one of the main factors influencing this characteristic
Summary
Renewable energy sources are currently among theIn order to allow the commercialization of FC in a most active research areas due to the global climate large scale, a significant cost reduction must be achieved, T changes and their consequences. The availability of starting materials and the possibility of changing SIPN composition allow the tuning of optimized properties such as high ionic conductivity; mechanical, chemical and dimensional stability at high temperatures and in oxidizing/reducing environments; low fuel permeability after water or methanol uptake and good contact with the interfaces between electrodes/ electrolyte.
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