Proton conducting electrolytes composed of chondroitin sulfate polysaccharide and citric acid

Santos, Filipe M.; Barbosa, Paula C.; Pereira, Rui F.P.; Silva, M. Manuela; Gonçalves, Helena M R; Nunes, Sílvia C.; Figueiredo, Filipe L.; Valente, Artur J.M.; Zea Bermudez, Verónica de

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Autores

Gonçalves, Helena M R

Nunes, Sílvia C.

Figueiredo, Filipe L.

Valente, Artur J.M.

Zea Bermudez, Verónica de

Resumo(s)

Novel electrolytes composed of chondroitin sulfate A (CSA) and citric acid (CA) have been prepared using a clean, safe, and fast route. These electrolytes exhibit different physical-chemical properties, depending on the amount of CA. For X > 82.3%, where X is the mass ratio, in %, of CA/(CA + CSA), whitish polycrystalline powders result. Lower amounts of CA leads to the production of translucent, amorphous films, sticky for X = 75.6 and 82.0, brittle for X < 43.6 and crack-free, self-standing for 43.6 < X < 75.6%. The results obtained provide evidence that, at low pH, strong hydrogen bonding interactions take place between the anionic sulfonic and carboxylic groups of CSA and CA. CA exerts a key role, acting as a cross-linker and proton source, while simultaneously influencing sample morphology. At room temperature the highest ionic conductivity is achieved at X = 60.8%. A significant enhancement of the ionic conductivity of this sample occurs with the increase of relative humidity (RH) (from 3.1 × 10−7 to 3.7 × 10−2 S cm−1 30% for RH = 30 and ~100%, respectively).