Carbonyl Groups in Sulfonated Styrene−Divinylbenzene Macroporous Resins

Scanning electrochemical microscopy for the differentiation of radical-induced degradation mechanisms in polymer electrolyte membranes

In this work, a spatially resolved analytical method based on scanning electrochemical microscopy (SECM) to distinguish different degradation phenomena in polymer electrolyte membranes was developed. SECM was combined with a Franz diffusion cell to distinguish between radical-induced aging of a sulfonated tetrafluoroethylene based fluoropolymer-copolymer due to deactivation of the sulfonic acid groups followed by a decreased proton conductivity, and the radical-induced formation of cracks and holes in the polymer. The experiments were performed with ferrocyanide as redox mediator to detect holes and cracks, and protons (sulfuric acid) to determine the through-plane proton conductivity, respectively. A pristine Nafion™ membrane, a pristine Nafion™ membrane with an artificial pinhole and a Nafion™ membrane aged with Fenton's reagent were investigated to prove the measurement principle. It could be shown that holes and cracks can be reliably detected with this approach and discriminated from a change in proton conductivity. The presence of holes in the investigated aged membranes was confirmed by scanning electron microscopy, whereas the loss of sulfonate groups could be supported by infrared spectroscopy measurements.

High-frequency fabrication of discrete and dispersible hollow carbon spheres with hierarchical porous shells by using secondary-crosslinking pyrolysis

Discrete, uniform HCSs with hierarchical porous shell are fabricated by “secondary-crosslinking pyrolysis”, showing high specific capacitance of 192 F g⁻¹.

Preparation of large micron-sized monodisperse polystyrene/silver core–shell microspheres with compact shell structure and their electrical conductive and catalytic properties

Large micron-sized monodisperse PS/Ag core–shell microspheres and their corresponding hollow Ag spheres were synthesized via an improved mild electroless plating strategy.

Formation of sulfonated aromatic ketone chromophores within styrene-acrylic acid copolymers and their pH-responsive color change

Styrene-acrylic acid copolymer was synthesized via solution polymerization and then sulfonated by concentrated sulfuric acid. This sulfonated copolymer displays an obvious pH-responsive color change in aqueous solutions (1 g/L) from yellow (pH <6) to khaki (pH 6 to 7)/red (pH 7 to 8) to purple (pH >8). This response is as quick as for small-molecule pH indicators such as methyl orange and phenolphthalein within 1 s and can be reversible. The lowest critical concentration of this pH-responsive copolymer solution is around 0.1 g/L, which is about 50-500 times the necessary amount used for conventional small-molecule pH indicators. An intramolecular cyclization mechanism between a neighboring carboxyl group and a benzene ring to form a sulfonated aromatic ketone is proposed to explain this pH-responsive color change behavior. The molar ratio of 1:1 for styrene to acrylic acid is the most favorable for forming neighboring benzene and carboxyl group pairs in the copolymer chains and subsequently yields sulfonated aromatic ketone chromophores at full capacity.