PEMs graft copolymer

Block and graft copolymers are composed of significant sequences of different monomer units, normally in a nonstatistical fashion. For block copolymers, these sequences are assembled in a linear fashion whereas in the case of graft copolymers, blocks are grown from or attached to the backbone of another block as branches. In the case of block and graft copolymer PEMs, these sequences may be composed of significantly different chemical units or units that are chemically identical except that one block is sulfonated and the other is not. 

As typically observed in the case of non-ionic block and graft copolymers, the immiscibility of the constituent blocks within the copolymers can induce microphase separation beyond even that which normally occurs due to hydrophobic and hydrophilic sites within statistical copolymer PEMs such as Nation. A relatively recent area of PEM research, ionic block and graft copolymers are interesting from the point of view of providing fundamental understanding about the influence of morphology upon proton conduction... 

Keywords Polyelectrolyte multilayer PEM poly (ethylene glycol) PEG graft copolymer FTIR-ATR adsorption... 

Thermal stability is an important property for PEMs, especially in high-temperature systems, and the corresponding characterization is thermogravimetric analysis (TGA). As most of the prepared aliphatic PEMs reported in the literature are block copolymers, graft copolymers, and composites of polymers, with frequently some inorganic materials included, TGA was used to study the differences between PEMs with different compositions [24,37,42,47],... 

As to the fabrication of PEMs, PVDF was usually used as a copolymer with hexafluoropropylene, indicated as PVDF-HFP. Kumar et al. have done much work on PVDF-HFP-based PEMs [29-33]. Since then, the copolymer was blended with other polymers or inorganic materials for ion introduction like Naflon, montmoril-lonite (MMT), and A10[0H]. Besides, PVDF has been grafted with PSSA or vinyl-imidazole (Vim) in some research works [34,35], and AI2O3, poly(ethylene glycol) (PEG), or poly(2-acrylamido-2-methyl-l-propanesulfonic acid) (PAMPS) have been used to blend with PVDF system [35,36]. In these researches, PVDF-based PEMs are designed mainly for DMFC application as well as DEFC. 

Copolymerization The copolymerization of the preceding aliphatic polymers with other polymers is another method to fabricate PEMs, in which block or graft copolymerization has been used. This method is easily used for designing different main chain structures. For the composition method, the base polymers were usually obtained from commercial products directly, whereas for the latter method, the copolymers should be synthesized in laboratory by the researchers. Via sequential atom transfer radical... 

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