Synthesis and properties of novel sulfonated polyimides containing binaphthyl groups as proton‐exchange membranes for fuel cells

Abstract

A novel sulfonated diamine monomer, 2,2′‐bis(p‐aminophenoxy)‐1,1′‐binaphthyl‐6,6′‐disulfonic acid (BNDADS), was synthesized. A series of sulfonated polyimide copolymers containing 30–80 mol % BNDADS as a hydrophilic component were prepared. The copolymers showed excellent solubility and good film‐forming capability. Atomic force microscopy phase images clearly showed hydrophilic/hydrophobic microphase separation. The relationship between the proton conductivity and degree of sulfonation was examined. The sulfonated polyimide copolymer with 60 mol % BNDADS showed higher proton conductivity (0.0945–0.161 S/cm) at 20–80 °C in liquid water. The membranes exhibited methanol permeability from 9 × 10−8 to 5 × 10−7 cm2/s at 20 °C, which was much lower than that of Nafion (2 × 10−6cm2/s). The copolymers were thermally stable up to 300 °C. The sulfonated polyimide copolymers with 30–60 mol % BNDADS showed reasonable mechanical strength; for example, the maximum tensile strength at break of the sulfonated polyimide copolymer with 40 mol % BNDADS was 80.6 MPa under high moisture conditions. The optimum concentration of BNDADS was found to be 60 mol % from the viewpoint of proton conductivity, methanol permeability, and membrane stability. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 222–231, 2007

In situ sol–gel route to novel sulfonated polyimideSiO2 hybrid proton‐exchange membranes for direct methanol fuel cells

“…Up to now, a large number of sulfonated polymers have been studied, such as poly(styrene sulfonic acid) and analogous polymers,16 sulfonated polysulfone,17 sulfonated poly(ether ether ketone),18 among others. Very recently, sulfonated polyimides (SPIs) have been reported as promising materials for use in PEFCs 19–22. High‐performance aromatic polyimides (PIs) have many technological applications, in particular in aerospace, advanced microelectronics and other advanced technologies, due to their excellent mechanical, thermal and dielectric properties 23, 24.…”

Soluble Polyimides Based on Long-chain Alkyl Groups via Amide Linkages

“…However, owing to the instability of poly(amic acid)s and the liberation of water in the imidization process, problems can arise. Extensive research has been recently carried out to improve the solubility of polyimides and successful examples involve the incorporation of fluorine moieties, [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] bulky side groups, [18][19][20][21][22][23][24] alicyclic structure, 25 spiro structure, 26 cardo groups, 27,28 pyridine moiety, 29,30 porphyrin moiety, 31 acridine moiety, 32 and sulfonated structure, [33][34][35][36] and the applications include the functional materials such as low-k material, 3,14,15,25 colorless or light-colored polyimides, 9,10,12 gas transport membranes, 16,17,24 electrochromism materials, 22 pervaporation membranes, 7 materials for organic light-emitting diode (OLED), 27,…”

Preparation and properties of ionic cross‐linked sulfonated copolyimide membranes containing pyrimidine groups

“…Unfortunately, high sulfonation level makes them excessively water‐swollen or even soluble in water. Therefore, highly sulfonated polyimide membranes lose their mechanical properties and become unavailable in applications 9–13…”