Proton conducting electrolytes composed of chondroitin sulfate polysaccharide and citric acid


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 x 10(-7) to 3.7 x 10(-2) S cm(-1) 30% for RH = 30 and similar to 100%, respectively).



subject category

Polymer Science


Santos, FM; Barbosa, PC; Pereira, RFP; Silva, MM; Goncalves, HMR; Nunes, SC; Figueiredo, FL; Valente, AJM; Bermudez, VD

our authors


Support by Fundacao para a Ciencia e Tecnologia, I.P. (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013, UID/QUI/00686/2013, UID/QUI/50006/2019 and UID/QUI/00686/2016. This work was funded by the R&D Project UniRCell-Unitised regenerative fuel cell for efficient renewable energy supply: from materials to device, with reference POCI-01-0145-FEDER-016422 and SAICTPAC/0032/2015, financed by the European Regional Development Fund (ERDF) through COMPETE 2020 - Operational Program for Competitiveness and Internationalization (FOCI) and by the Foundation for Science and Technology (FCT) and CICECO-Aveiro Institute of Materials (UID/CTM/50011/2019), financed by national funds through the FCT/MEC. Is also acknowledged, as well as funding under projects UID/CTM/50025/2013, Pest-OE/QUI/UI0616/2014, and LUMECD (PTDC/CTM/NAN/0956/20149 and POCI-01-0145-FEDER-016884). F. M. Santos acknowledges a Post-PhD Fellow grant supported by Project UniRcell. P. C. Barbosa employment contract is funded by national funds (OE), through FCT - Fundacao para a Ciencia e a Tecnologia, I.P., in the scope of the framework contract foreseen in the numbers 4, 5 and 6 of the article 23, of the Decree - Law 57/2016, of August 29, changed by Law 57/2017, of July 19. R. F. P. Pereira Post-PhD fellow was funded by FCT (SFRH/BPD/87759/2012). S. C. Nunes was funded by FCT projects (Post-PhD Fellowships of UniRCell and LUMECD projects). H.M.R. Goncalves was funded by NORTE-01-0145-FEDER-030858 and PTDC/BTM-MAT/30858/2017.

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