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Embedding of Hollow Polymer Microspheres with Hydrophilic Shell in Nafion Matrix as Proton and Water Micro-Reservoir
Department of Chemical & Biomolecular Engineering, National University of Singapore, 10 Kent Ridge Crescent, 119260, Singapore
Institute of Materials Research and Engineering, 3 Research Link, 117602, Singapore
* Author to whom correspondence should be addressed.
Received: 19 June 2012; in revised form: 1 August 2012 / Accepted: 10 August 2012 / Published: 20 August 2012
Abstract: Assimilating hydrophilic hollow polymer spheres (HPS) into Nafion matrix by a loading of 0.5 wt % led to a restructured hydrophilic channel, composed of the pendant sulfonic acid groups (–SO3H) and the imbedded hydrophilic hollow spheres. The tiny hydrophilic hollow chamber was critical to retaining moisture and facilitating proton transfer in the composite membranes. To obtain such a tiny cavity structure, the synthesis included selective generation of a hydrophilic polymer shell on silica microsphere template and the subsequent removal of the template by etching. The hydrophilic HPS (100–200 nm) possessed two different spherical shells, the styrenic network with pendant sulfonic acid groups and with methacrylic acid groups, respectively. By behaving as microreservoirs of water, the hydrophilic HPS promoted the Grotthus mechanism and, hence, enhanced proton transport efficiency through the inter-sphere path. In addition, the HPS with the –SO3H borne shell played a more effective role than those with the –CO2H borne shell in augmenting proton transport, in particular under low humidity or at medium temperatures. Single H2-PEMFC test at 70 °C using dry H2/O2 further verified the impactful role of hydrophilic HPS in sustaining higher proton flux as compared to pristine Nafion membrane.
Keywords: hollow polymer microspheres; keeping moisture; composite membrane; PEM fuel cell
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MDPI and ACS Style
Guo, B.; Tay, S.W.; Liu, Z.; Hong, L. Embedding of Hollow Polymer Microspheres with Hydrophilic Shell in Nafion Matrix as Proton and Water Micro-Reservoir. Polymers 2012, 4, 1499-1516.
Guo B, Tay SW, Liu Z, Hong L. Embedding of Hollow Polymer Microspheres with Hydrophilic Shell in Nafion Matrix as Proton and Water Micro-Reservoir. Polymers. 2012; 4(3):1499-1516.
Guo, Bing; Tay, Siok Wei; Liu, Zhaolin; Hong, Liang. 2012. "Embedding of Hollow Polymer Microspheres with Hydrophilic Shell in Nafion Matrix as Proton and Water Micro-Reservoir." Polymers 4, no. 3: 1499-1516.