Poly benzimidazole blends

One of the first examples of this type of blend was composed of SPEEK or SPES as the acidic component and diaminated PES, poly(4-vinylpyridine) (P4VP), poly(benzimidazole) (PBl), or poly(ethyleneimine) (PEI) as the basic component. " For blend lEC values of 1.0 meq/g, conductivity values were reported to be good, as was H2/O2 EC performance. Thermal stabilities for these blends was also demonstrated to be high (>270°C). Other examples of acid-base PEMs include blends of SPPO and PBI, sulfonated poly(phthalazinone ether ketone) and aminated SPES, SPIs and aminated Pls, and SPEEK with PES bearing benzimidazole side groups, ° as well as an unusual example in which the blend is composed of sulfonated, hyper-branched polyether and pyridine-functionalized polysulfone. ... 

MacKnight and coworkers found that several poly(imide)s, such as Ultem poly(ether imide) and XU218 poly(imide), formed miscible blends with poly (benzimidazole) (FBI) [58, 59]. The miscibility of these blends is believed to result from specific interactions between the benzimide ring of the poly(im-ide) and benzimidazole ring of FBI. In a later study, Grobelny et al. [60] reported the CFMAS spectra of several of these blends. Slight changes in the lineshape were observed in the intimate blends, and seen as evidence of the specific interactions between the polymers. In particular, the peak in the spectra, due to the imide carbonyl carbon, was seen to broaden towards... 

There are also some specialized fibers, such as flame-retardant fibers. They are utilized, for example, in hotel blankets, subway seats, and in aircraft. There are two methods of introducing flame retard-ancy. One is to blend in flame-retardant agents during the making of the fibers. Most flame-retardant agents are organophosphorus compounds. The other is to make inherently flame-retardant synthetic fibers. Some of these fibers are composed of poly( benzimidazole) and an aromatic copolyamide. 

A similar synergistic effect in the physical properties of blends was observed by Cho et al. (2000) who studies novel blends of nitro-substituted poly(benzimidazole) (NO2 - PBI) and poly(etherimide) (PEI) in a cosolvent. The blends possess tractable processability owing to the enhanced solubility of NO2 - PBI. Miscilbility was observed and attributed to hydrogen bonding between the N-H groups of the NO2-PBI and the carbonyl groups in the PEI. 

High-molecular/low-molecular composites such as blends of poly (benzimidazoles) with phosphoric acid as the proton-conducting component or phosphoric acid blended into other organopolymers [24-27], or blends of a sulfonated polymer with amphoterics such as imidazoles or pyrazoles or imidazole-containing oligomers or polymers alone [28,29], or blends of sulfonated polymers with heteropolyacids [30-32]. 

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, Y. Z., Manthiram, A. and Guiver, M. D. 2006. Blend membranes based on sulfonated poly(ether ether ketone) and polysulfone bearing benzimidazole side groups for proton exchange membrane fuel cells. Electrochemistry... 

One of the basic problems confronting molecular composites is the difficulty of finding miscible combinations of rigid rod polymers with flexible chain polymers. Poly(p-phenylene benzobisthiazole)/poly(-2,5(6)-benzimidazole block copolymers have been reported by Tsai et al. [1985] and are noted to exhibit better processability and mechanical properties than the simple blends of the block copolymer constituents. Chang and Lee [1993] prepared poly(p-benzamide)/Pl block copolymers and reported on the liquid crystalline behavior. Such approaches would appear to have future implications. As an example PA e.g., PA-66) block copolymers with rigid rod polyamides could be prepared and used in blends with PA-66 to yield the desired molecular composite. 

Fu Y, Manthiram A, Culver MD (2007) Acid-base blend membranes based on 2-amino-benzimidazole and sulfonated poly(ether ether ketone) for direct methanol fuel cells. Electrochem Commun 9 905-910... 

Acar O, Sen U, Bozkurt A, Ata A (2009) Proton coneluering membranes based on poly (2,5-benzimidazole) (ABPBI)-poly(vinylphosphonic acid) blends for fuel cells. Int J Hydrogen Energ 34 2724—2730... 

Kreuer et al. [66] doped sulfonated poly(ether ether ketone) (sPEEK) by immersing it into liquid pyrazole and imidazole. A base doping level of 2.3-10, defined as the molar ratio of [C3N2H4]/[-S03H], could be achieved. The intercalation of imidazole and pyrazole into polymers with Brpnsted acid sites is shown to enhance the protonic conductivity. Of the two basic solvents of protons, pyrazole has a lower tendency for the molecular association by hydrogen bonding and therefore a lower proton conductivity, as compared with imidazole. Fu et al. [81, 82] studied acid-base blends based on 2-aminobenzimidazole and sPEEK. They proposed that benzimidazole is protonated by the sulfonic acid, as evidenced by the symmetric stretching of the S-O bonds in FTIR spectra. 

Fu et al. [11] reported the acid-base blend membranes based on 2-amino-benzimidazole (basic polymer) and sulfonated poly(ether ether ketone) (SPEEK) (acidic polymer) for direct methanol fuel cells. A novel polymer, polysulfone-2-amide-benzimidazole (PSf-ABIm), using carboxylated polysulfone and 2-amino-benzimidazole was synthesized for this purpose. The blend membrane of SPEEK/PSf-ABIm showed high performance a s represented by Figure 1.12. The blend membrane with 3 wt% PSf-ABIm was evaluated continuously for 120 h and little or no decline in performance was found after 120 h. On the other hand, the Nafion 112 membrane standard was observed to have a decline in performance due to a much higher amount of methanol crossover. 

Organic components can also be introduced in perfluorinated membranes, to increase the membrane selectivity. Polyvinylidene (PVDF) can effectively suppress the swelling of Nafion due to its high crystallite nature and further improve the selectivity [17]. By simple blending of PVDF with Nafion, the CE of the battery can be improved due to its higher ion selectivity, and the EE increases as well. The use of acid-base membranes such as SPEEK (sulphonated poly(ether ether ketone)), and PSf-ABIm (polysulphone-2-amide-benzimidazole) is another way to improve membrane selectivity via the interactions between sulphonated acid and amide basic groups [18,19]. 

Sen, U Acar, O. Bozkurt, A. and Ata, A., Proton conducting polymer blends from poly(2,5-benzimidazole) and poly(2-acrylamido-2-methyl-1-propane-sulfonic acid), J. Appl. Polym. Set, 120(2), 1193-1198 (2011) DOI 10.1002/ app.33026. 

---