Fengyan Fu

Synthesis and characterization of sulfonated polyphosphazene-graft-polystyrene copolymers for proton exchange membranes

A novel series of polyphosphazene-graft-polystyrene (PP-g-PS) copolymers were successfully prepared by atom transfer radical polymerization (ATRP) of styrene monomers and brominated poly(bis(4-methylphenoxy)phosphazene) macroinitiator. The graft density and the graft length could be regulated by changing the bromination degree of the macroinitiator and the ATRP reaction time, respectively. The PP-g-PS copolymers readily underwent a regioselective sulfonation reaction, which occurred preferentially at the polystyrene sites, producing the sulfonated PP-g-PS copolymers with a range of ion exchange capacities. The resulting sulfonated PP-g-PS membranes prepared by solution casting showed high water uptake, low water swelling and considerable proton conductivity. They also exhibited good oxidative stability and high resistance to methanol crossover. Morphological studies of the membranes by transmission electron microscopy showed clear nanophase-separated structures resulted from hydrophobic polyphosphazene backbone and hydrophilic polystyrene sulfonic acid segments, indicating the formation of proton transferring tunnels. Therefore, these sulfonated copolymers may be candidate materials for proton exchange membranes in direct methanol fuel cell (DMFC) applications.

Copper-Catalyzed Asymmetric Synthesis and Comparative Aldose Reductase Inhibition Activity of (+)/(−)-1,2-Benzothiazine-1,1-dioxide Acetic Acid Derivatives

A copper catalyst system for the asymmetric 1,4-hydrosilylation of the α,β-unsaturated carboxylate class was developed by which synthesis of (+)- and (-)-enantiomers of 1,2-benzothiazine-1,1-dioxide acetates has been achieved with a good yield and an excellent level of enantioselectivity. A comparative structure-activity relationship study yielded the following order of aldose reductase inhibition activity: (-)-enantiomers > racemic > (+)-enantiomers. Further, a molecular docking study suggested that the (-)-enantiomer had significant binding affinity and thus increased inhibition activity.

Chiral resolution, determination of absolute configuration, and biological evaluation of (1,2-benzothiazin-4-yl)acetic acid enantiomers as aldose reductase inhibitors

Abstract A novel series of (1,2-benzothiazin-4-yl)acetic acid enantiomers was prepared by chiral resolution, and their absolute configurations were determined using the PGME method. The biological evaluation of the racemate and single enantiomers has shown a remarkable difference for the aldose reductase inhibitory activity and selectivity. The (R)-(−)-enantiomer exhibited the strongest aldose reductase activity with an IC50 value of 0.120 μM, which was 35 times more active than the S-(+)-enantiomer. Thus, the stereocenter at the C4 position of this scaffold was shown to have a major impact on the activity and selectivity.

Composite polyphosphazene membranes doped with phosphotungstic acid and silica

Poly(bis(phenoxy)phosphazene) (SPBPP)/phosphotungstic acid (PWA)/silica composite membranes for fuel cells were prepared. The composite membranes were characterized by using FTIR, TGA and SEM techniquies. Incorporation of PWA particles and silica particles into the SPBPP polymer matrix and a specific interaction between them were confirmed by FTIR spectra. TGA results showed that the composite membranes had high thermal stability. Homogeneous distribution of PWA and silica particles within the SPBPP matrix was verified by SEM micrographs. The doped membranes showed increased water uptake and proton conductivity.

Synthesis and Characterization of Perfluoroalkyl Sulfonic Acid Functionalized Polyphosphazene for Proton-Conducting Membranes

Polyphosphazenes containing perfluoroalkyl sulfonic acids (PSA-P) were synthesized by the copper-catalyzed coupling reaction of poly[(4-bromophenoxy)(phenoxy)phosphazene] with potassium 1,1,2,2-tetrafluoro-2-(1,1,2,2-tetrafluoro-2-iodoethoxy) ethanesulfonate. Two synthetic protocols have been developed to obtain the polymers and 1, 10-phenanthroline was found benefit for improving the efficiency of the coupling reaction. The PSA-P membranes prepared by solution casting showed excellent thermal stability, oxidative stability and low swelling ratios. In addition, compared with the sulfonated poly[bis(phenoxy)phosphazene] membrane with similar IEC, the PSA-P membrane displayed significant superiority in proton conductivity, water resistance, oxidative and thermal stability, indicating that it is a good candidate for proton exchange membranes.