: 1h nmr spectra of a series of enaminones r-co-ch=c(nhch2ph)-r  [1, r=ch3; 2, r=c6h5; 3, r=cf3; 4, r=ch2ch2ch2; 5, r=ch2c(ch3)2ch2], were obtained in the presence of trifluoroacetic acid in cdcl3 or dmso-d6 at 28 °c. steric, solvent, electronic and hydrogen bonding effects on the rates of acid-catalyzed nh proton exchanges were investigated. rate constants were calculated by 1h nmr line shape ...

heterogeneous proton exchange membranes (pem) are synthesized using the dry phase inversion technique. the casting solutions are prepared by dispersing a finely ground cation exchange resin particle in n,n-dimethylacetamide (dmac) solution of polyvinyl-chloride (pvc). results show that ion exchange capacity is increased with the addition of 1 %-wt nanosilica (from 0.14 to 0.27 meq/g) while it i...

sulfonated poly (ether ether ketone) (speek) with a low degree of sulfonation (ds = 40%) was prepared for proton exchange membrane fuel cells (pemfc). poly (ether ether ketone) (peek) was sulfonated in concentrated h2so4 under n2 atmosphere and characterized by the hydrogen nuclear magnetic resonance (h-nmr) technique. after preparation of the speek polymer, the obtained polymer was dissolved i...

In this study, proton conductive composite membranes were produced by using a poly(methylmethacrylate-co-maleic anhydride) (P(MMA-co-MAH)) copolymer and phosphotungstic Acid (PWA) as an additive of the proton conductive agent. P(MMA/MAH) 70/30, 50/50, and 30/70 were synthesized using a free radical polymerization reaction. PWA with a concentration of 2% was added to...

in the current work, graphene oxide (go) samples were prepared at room temperature from graphite flakes using a modified hummer's method to produce metal-free electrocatalysts. the effect of the duration of the oxidation process on the structural, chemical and physical characteristics of the go samples was evaluated using x-ray diffraction (xrd), fourier transform infrared spectroscopy (ftir), ...

Heterogeneous proton exchange membranes (PEM) are synthesized using the dry phase inversion technique. The casting solutions are prepared by dispersing a finely ground cation exchange resin particle in N,N-dimethylacetamide (DMAc) solution of polyvinyl-chloride (PVC). Results show that ion exchange capacity is increased with the addition of 1 %-wt nanosilica (from 0.14 to 0.27 meq/g) while it i...

proton exchange membrane fuel cells (pemfcs) are electrochemical devices that show the highest power densities compared to the other type of fuel cell. in this work, nanocomposite membranes used for proton exchange membrane fuel cells as poly(vinyl alcohol)/la2ce2o7 (pva-lc) with the aim of increasing the water uptake and proton conductivity. glutaraldehyde (ga) was used as cross linking agent ...

Proton exchange membrane fuel cells (PEMFCs) are electrochemical devices that show the highest power densities compared to the other type of fuel cell. In this work, nanocomposite membranes used for proton exchange membrane fuel cells as poly(vinyl alcohol)/La2Ce2O7 (PVA-LC) with the aim of increasing the water uptake and proton conductivity. Glutaraldehyde (GA) was used as cross linking agent ...

Sulfonated poly (ether ether ketone) (SPEEK) with a low degree of sulfonation (DS = 40%) was prepared for proton exchange membrane fuel cells (PEMFC). Poly (ether ether ketone) (PEEK) was sulfonated in concentrated H2SO4 under N2 atmosphere and characterized by the hydrogen nuclear magnetic resonance (H-NMR) technique. After preparation of the SPEEK polymer, the obtained polymer was dissolved i...