DMFC Performance of Polymer Electrolyte Membranes Prepared from a Graft-Copolymer Consisting of a Polysulfone Main Chain and Styrene Sulfonic Acid Side Chains
Polymer electrolyte membranes (PEMs) for direct methanol fuel cell (DMFC) applications were prepared from a graft-copolymer (PSF- g -PSSA) consisting of a polysulfone (PSF) main chain and poly(styrene sulfonic acid) (PSSA) side chains with various average distances between side chains ( L av) and side chain lengths ( L sc). The polymers were synthesized by grafting ethyl p -styrenesulfonate (EtSS) on macro-initiators of chloromethylated polysulfone with different contents of chloromethyl (CM) groups, and by changing EtSS content in the copolymers by using atom transfer radical polymerization (ATRP). The DMFC performance tests using membrane electrode assemblis (MEAs) with the three types of the PEMs revealed that: a PSF- g -PSSA PEM (SF-6) prepared from a graft copolymer with short average distances between side chains ( L av) and medium L sc had higher DMFC performance than PEMs with long L av and long L sc or with short L av and short L sc. SF-6 had about two times higher PD max (68.4 mW/cm 2 ) than Nafion ® 112 at 30 wt % of methanol concentration. Furthermore, it had 58.2 mW/cm 2 of PD max at 50 wt % of methanol concentration because of it has the highest proton selectivity during DMFC operation of all the PSF- g -PSSA PEMs and Nafion ® 112.
Methanol permeability and proton conductivity of sulfonated co-polyimide membranes
Abstract Two types of sulfonated co-polyimides (co-SPIs) with ion exchange capacities of 1.83–2.32 meq/g were prepared from 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), two types of sulfonated diamines, namely, 4,4′-bis(4-sulfophenoxy)biphenyl-3,3′-disulfonic acid (BAPBDS) and bis(3-sulfopropoxy)benzidines (BSPBs), and common non-sulfonated diamines via statistical polycondensation reaction. The BSPB-based co-SPI membranes had a clear microphase-separated structure composed of hydrophilic and hydrophobic domains but the connection of hydrophilic domains was rather poor. On the other hand, the BAPBDS-based co-SPI membranes did not show such a clear microphase separation. The co-SPI membranes except for a few ones showed high proton conductivities of 0.10–0.16 S/cm in water at 323 K, which was comparable to that of Nafion 112 (0.13 S/cm). The methanol permeabilities of the co-SPI membranes hardly depended on feed composition up to 50 wt.% of methanol and were in the range of 0.5 × 10 −6 to 1.8 × 10 −6  cm 2 /s at 323 K, which were more than two times smaller than those of Nafion 112. As a result, the co-SPI membranes showed more than two times larger ratios of proton conductivity over methanol permeability than Nafion, suggesting high potential for direct methanol fuel cell application.
Synthesis and properties of nonlinear optical side chain soluble polyimides for photonics applications
Aromatic polyimides with side chain nonlinear optical chromophores have been investigated through a facile two-step synthetic route. First, various poly(hydroxy imide)s have been synthesized by direct thermal imidization of diaminophenol dihydrochloride salt and aromatic dianhydride monomers. The resulting polyimides bearing phenolic hydroxy groups were found to react easily with the terminal hydroxy group on the chromophores via the Mitsunobu condensation to give corresponding polyimides with high optical nonlinearities and good solubility in common organic solvents. Detailed physical properties showed that these polyimides have a molecular weight (M ω ) of 31,000 and high glass transition temperature above 220°C, ensuring a long-term alignment stability at elevated temperature. The electrooptic coefficients, r 33 , of the electrically poled polymer films were in the range 1.8-7.6 pm/V at 1.3 μm.