Polymer/polymeric electrolyte membrane

Boroxine ring-containing polymers have found extensive use in the development of polymeric electrolyte materials used in ion-selective transport membranes. Matsumi and Ohno cover this area in Chapter 6 of this book. 

Schematic depiction of the structural evolution of polymer electrolyte membranes. The primary chemical structure of the Nafion-type ionomer on the left with hydrophobic backbone, side chains, and acid head groups evolves into polymeric aggregates with complex interfacial structure (middle). Randomly interconnected phases of these aggregates and water-filled voids between them form the heterogeneous membrane morphology at the macroscopic scale (right).

Some of the most useful polyphosphazenes are fluoroalkoxy derivatives and amorphous copolymers (11.27) that are practicable as flame-retardant, hydrocarbon solvent- and oil-resistant elastomers, which have found aerospace and automotive applications. Polymers such as the amorphous comb polymer poly[bis(methoxyethoxyethoxy)phosphazene] (11.28) weakly coordinate Li " ions and are of substantial interest as components of polymeric electrolytes in battery technology. Polyphosphazenes are also of interest as biomedical materials and bioinert, bioactive, membrane-forming and bioerodable materials and hydrogels have been prepared. 

The development of transparent polymer electrolyte membrane from the bi-continuous-microemulsion polymerization of 4-vinylbenzene sulfonic acid Hthium salt (VBSIi), acrylonitrile and a polymerizable non-ionic surfactant, co-methoxypoly(ethylene oxide)4o-undecyl-a-methacrylate (Ci-PEO-Cn-MA-40) was reported in 1999 [94,95]. The ionic conductivities of the polymer electro-... 

Many different kinds of fuel cells are presently known, most of them suitable for high-temperature applications— for details see Ref. [101]. The polymeric proton-conducting membranes (polymer electrolyte membranes PEM) are however suitable for low temperamre operations (<100°C) and have the advantage of low weight. 

The development of new polymeric materials for polymer electrolyte fuel cell is one of the most active research areas, aiming at the new energy sources for electric cars and other devices. The mainstream of the material research for fuel cell is perfluoroalkyl sulfonic acid membranes such as Nafion, Acipex, and Flemion. The most well-known one is Nafion of Du Pont, which is derived from copolymers of tetrafluoro-ethylene and perfluorovinyl ether terminated by a sulfonic acid group.Protons, when dissociated from the sulfonic acid groups in aqueous environment, become mobile and the membrane becomes a proton conducting electrolyte membrane. 

Many approaches have been developed for the production of ionic liquid-polymer composite membranes. For example, Doyle et al. [165] prepared RTILs/PFSA composite membranes by swelling the Nafion with ionic liquids. When 1-butyl, 3-methyl imidazolium trifluoromethane sulfonate was used as the ionic liquid, the ionic conductivity ofthe composite membrane exceeded 0.1 S cm at 180 °C. A comparison between the ionic liquid-swollen membrane and the liquid itself indicated substantial proton mobility in these composites. Fuller et al. [166] prepared ionic liquid-polymer gel electrolytes by blending hydrophilic RTILs into a poly(vinylidene fiuoridej-hexafluoropropylene copolymer [PVdF(HFP)] matrix. The gel electrolytes prepared with an ionic liquid PVdF(HFP) mass ratio of 2 1 exhibited ionic conductivities >10 Scm at room temperature, and >10 Scm at 100 °C. When Noda and Watanabe [167] investigated the in situ polymerization of vinyl monomers in the RTILs, they produced suitable vinyl monomers that provided transparent, mechanically strong and highly conductive polymer electrolyte films. As an example, a 2-hydroxyethyl methacrylate network polymer in which BPBF4 was dissolved exhibited an ionic conductivity of 10 S cm at 30 °C. 

The proton exchange membrane - also known as polymer electrolyte membrane (PEM) - fuel cell uses a polymeric electrolyte. The protonconducting polymer forms the heart of each cell electrodes, usually made of porous carbon with catalytic platinum incorporated into them, are bonded to either side of the electrolyte to form a one-piece membrane-electrode assembly (MEA). The following are some key advantages that make PEMs such a promising technology for the automotive market ... 

The temperature of operation of polymer electrolyte membrane fuel cells tends to get higher, because certain advantages are faced, such as improved tolerance of carbon monoxide, the improved ease of water and heat management, and increased energy efficiency. However, several commonly used polymeric membranes cannot withstand the high temperatures. Therefore, there is a need to look for alternative materials. 

Polymeric functional materials are of central importance for the polymer electrolyte membrane fuel cell (PEMFC) and DMFC technologies in particular. In addition to the expected cost reduction due to low-cost mass productimi, for example of polymeric bipolar plates (see Sect. 2.1), the polymeric membranes are irreplaceable in the PFMFC and DMFC technologies. 

Polymer electrolyte fuel cells (PEFCs) have attracted much interest as one of the most promising nonpolluting power sources capable of producing electrical energy with high thermodynamic efficiencies. The key element of PEFCs is a polymer electrolyte membrane (PEM) that serves as proton conductor and gas separator [1, 2, 3,4], The membrane commonly employed in most PEFC developments is based on Nafion, which represents a family of comb-shaped ionomers with a perfiuorinated polymeric backbone and short pendant (side) chains having sulfonic acid end groups... 

The discovery and the characterization of ionically conducting polymeric membranes (see Chapters 1 and 2) have provided the interesting possibility of developing new types of lithium batteries having a thin-layer, laminated structure. Various academic and industrial laboratories [1-5] are presently engaged in the development of this revolutionary type of battery, i.e. the so-called Lithium Polymer Battery (LPB). The key component of the LPB is the polymeric ionic membrane which acts both as electrolyte and separator furthermore, the membrane can be easily fabricated in the form of a thin film (typically 50 jum thickness) by a number of convenient casting techniques. 

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