Acid-base polymer blend membrane

J. Kerres, A. Ullrich, Synthesis of novel engineering polymers containing basic side groups and their application in acid-base polymer blend membranes, Sep. Purif. Technol. 22, 1-15 (2001)... 

Trogadas and Ramani summarized the modification of PEM membranes, including Nafion modified by zirconium phosphates, heteropolyacids, hydrogen sulfates, metal oxides, and silica. Membranes with sulfonated non-fluorinated backbones were also described. The base polymers polysulfone, poly(ether sulfone), poly(ether ether ketone), polybenzimidazole, and polyimide. Another interesting category is acid-base polymer blend membranes. This review also paid special attention to electrode designs based on catalyst particles bound by a hydrophobic poly-tetrafluoroethylene (PTFE) structure or hydrophilic Nafion, vacuum deposition, and electrodeposition method. Issues related to the MEA were presented. In then-study on composite membranes, the effects of particle sizes, cation sizes, number of protons, etc., of HPA were correlated with the fuel cell performance. To promote stability of the PTA within the membrane matrix, the investigators have employed PTA supported on metal oxides such as silicon dioxide as additives to Nafion. 

Pasupathi et al. fabricated an acid-base polymer blend membrane based on sulfonated poly(etheretherketone) and poly(benzimidazole) for direct methanol fuel cells. A SPEEK/PBI membrane demonstrated a noticeable enhancement in the DMFC performance compared with Nafion 117. The maximum power densities (45 mW cm ) obtained with SPEEK/PBI membranes were twice that of Nafion 117 at 60 °C. This membrane maintained high power densities for more than 50 days of operation and therefore is seen as a potential candidate for portable DMFC applications [89]. 

Fu, R.-Q. Julius, D. Hong, L. Lee, J.-Y, PPO-based acid-base polymer blend membranes for direct methanol fuel cells, /. Membr. Sci., 322(2), 331-338 (2008). 

Kerres, J., Ullrich, A., Meier, R and Haring, T. 1999. Synthesis and characterization of novel acid-base polymer blends for application in membrane fuel cells. Solid State Ionics 125 243-249. 

Cui W, Kerres J (2001) Acid-base polymer blends and their application in membrane processes. US Patent 6,194,474... 

Acid-base and blend membranes are alternative candidates for hybrid/composite polyelectrolytes. " Fully aromatic polymers are currently widely used polymer blenders except for Nation itself. The purpose for acid-base blending is to find an optimal compromise between enhancement of proton conductivity by sulfonation and improvement of thermal and morphological stability by composition. In blend composite membranes, the majority partner should ensure good proton-conducting behavior, and the minority partner should improve the mechanical properties and... 

Nam, K. et al., Acid-Base Proton Conducting Polymer Blend Membrane, U.S. Patent Application 2003/0219640, November 27, 2003. 

Savinell and co-workers, [105-107], who have principally studied phosphoric acid doped polybenzimidazole (PBl). Similar systems have been reported by He and co-workers [108], who in addition report the conductivities of PBl based membranes doped with PTA and zirconium hydrogen phosphate [108], Acid-base interactions in entirely polymeric systems have been reported by Kerres and co-workers [102], who prepared and stndied several membranes prepared by blending polymers with acidic (snlfonated-PEEK, sulfonated polyethersulfone) and basic (polybenzimidazole, poly-vinylpyridine) characteristics. Selected acid-base polymer systems are discnssed in the following. 

A significant number of works are concerned with the development of new membranes for the separation of mixtures of aromatic/alicyclic hydrocarbons [10,11,77-109]. For example, the following works can be mentioned. A mixture of cellulose ester and polyphosphonate ester (50 wt%) was used for benzene/cyclohexane separation [113]. High values of the separation factor and flux were achieved (up to 2 kg/m h). In order to achieve better fluxes and separation factors the attention was shifted to the modification of polymers by grafting technique. Grafted membranes were made of polyvinylidene fluoride with 4-vinyl pyridine or acrylic acid by irradiation [83]. 2-Hydroxy-3-(diethyl-amino) propyl methacrylate-styrene copolymer membranes with cyanuric chloride were prepared, which exhibited a superior separation factor /3p= 190 for a feed aromatic component concentration of 20 wt%. Graft copolymer membranes based on 2-hydroxyethyl methylacrylate-methylacrylate with thickness 10 pm were prepared [85]. The membranes yielded a flux of 0.7 kg/m h (for feed with 50 wt% of benzene) and excellent selectivity. Benzene concentration in permeate was about 100 wt%. A membrane based on polyvinyl alcohol and polyallyl amine was prepared [87]. For a feed containing 10 wt% of benzene the blend membrane yielded a flux of 1-3 kg/m h and a separation factor of 62. 

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