Green electrolyte host based on synthesized benzoyl kappa-carrageenan: Reduced hydrophilicity and improved conductivity

Newly synthesized benzoyl kappa carrageenan (Bz-ƙcar) was successfully produced by the Friedel Craft acylation method. The successful substitution of benzoyl molecule into kappa carrageenan (ƙcar) polymeric chain was confirmed by the FTIR analysis based on the formation of new carbonyl (CO) and CC bonds in Bz-ƙcar. 1H NMR analysis further proved the benzoylation by the appearance of new multiple resonances peaks at δ = 6.6–9.50 ppm, which belonged to the characteristic signals of protons in the aromatic benzoate group. XRD analysis showed reduced crystallinity of the synthesised carrageenan, while elemental analyser analysis revealed the increased percentages of carbon in Bz-ƙcar upon the substitution. The highest degree of substitution obtained was 0.27. TGA showed lower degradation temperature in the synthesised carrageenan, while water contact angle analysis demonstrated that Bz-ƙcar was less hydrophilic as compared to the pristine ƙcar. Solubility tests showed that Bz-ƙcar was best dissolved in ethylene glycol. The benzoylation also improved the ionic conductivity of Bz-ƙcar to 3.10 × 10−4 Scm−1 at ambient temperature.