Preparation of semi-interpenetrating polymer networks with adjustable mesh width and hydrophobicity

• Published in: Polymer (Guilford) Vol. 54; no. 1; pp. 134 - 142
• Main Authors: Fang, Chunliu, Julius, David, Tay, Siok Wei, Hong, Liang, Lee, Jim Yang
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 08.01.2013; Elsevier
• Subjects: alkylation; Applied sciences; bromination; Chemical modifications; Chemical reactions and properties; crosslinking; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Exchange resins and membranes; Forms of application and semi-finished materials; Fuel cells; hydrophobicity; methanol; Organic polymers; permeability; Physicochemistry of polymers; Poly(2,6-dimethyl-1,4-phenylene oxide); Polymer industry, paints, wood; polymers; Proton exchange membrane; Semi-interpenetrating polymer network; sulfonic acid; Technology of polymers; water uptake; Proton exchange membrane; Semi-interpenetrating polymer network; Poly(2,6-dimethyl-1,4-phenylene oxide); Structure effect; Transport properties; Voltage current curve; Size stability; Aromatic polymer; Ether polymer; Proton conductivity; Proton exchange membrane fuel cells; Methanol; Electrical properties; Bromine containing polymer; Crosslinking; Semiinterpenetrating polymer network; Experimental study; Functional polymer; Hydrophily; Diamine; Sulfonate polymer; Cation exchange capacity; Morphology; Preparation; Cation exchange membrane; Liquid permeability
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2012.11.069

Proton exchange membranes (PEMs) with a semi-interpenetrating polymer network (SIPN) structure were prepared by cross-linking brominated poly(2,6-dimethyl-1,4-phenylene oxide) (BPPO) with different aliphatic α,ω-diamine cross-linkers in the presence of sulfonated PPO (SPPO). The alkylation of the α,ω-diamine with BPPO resulted in a covalently cross-linked BPPO network where SPPO could be immobilized by interlocking. The interlocked structure was also strengthened by ion pair interactions between the sulfonic acid groups of SPPO and the amine moieties formed in cross-linking. The length of the aliphatic α,ω-diamine cross-linker was varied to modify the hydrophobicity and the mesh width (the average distance between two cross-linked polymer segments) of the cross-linked network host. The effects of these adjustments on the structure of the cross-linked network host were evaluated by the morphology of the hydrophilic domains, and transport properties such as proton conductivity and methanol permeability. It was found that the increase in mesh width and hydrophobicity of networks formed by long cross-linkers resulted in more scattered hydrophilic domains and fewer contiguous connections. On the contrary, the hydrophilic domains in networks with short cross-linkers were closer and more extensively-connected to facilitate proton transport. Methanol crossover in the SIPN membranes, on the other hand, could be suppressed by downsizing the size of the hydrophilic domains. Overall water uptake and dimensional swelling of the membranes were also affected by the cross-linker length. Some of the SIPN membranes delivered better performance than the Nafion® 117 membrane in single stack fuel cell tests, demonstrating the potential of SIPNs for the construction of fuel cell PEMs. [Display omitted]