Carbamate-functional, biobased surfactants derived from cardanol, carbon dioxide, and amino acids: Their synthesis and properties

Abstract

Three biobased, CO₂-consuming, and carbamate-groups-containing surfactants (CC-G, CC-T, CC-L) were synthesized separately by combination of Cardanol, CO₂, Glycine sodium salt (G), Taurine sodium salt (T), and Lysine sodium salt (L). The chemical structures of CC-G, CC-T, CC-L were confirmed by ¹H NMR and IR spectra. Thermal properties of these surfactants were studied with TGA and DSC. Their critical micelle concentration (CMC) and surface tension at CMC (${\rm Y}$_CMC) in aqueous solution were obtained by surface tension and conductivity methods, respectively. The amount of excess concentration (${\Gamma }_{\max }$) and the average occupied surface area ($A_{\min }$) of three surfactants were calculated. ${\Gamma }_{\max }$ of CC-G, CC-T and CC-L was 2.35 × 10⁻⁷ mmol/m², 2.23 × 10⁻⁷ mmol/m², and 6.16 × 10⁻⁷ mmol/m², separately. $A_{\min }$ of CC-G was 0.71 nm²/mmol, CC-T 0.74 nm²/mmol, CC-L 2.70 nm²/mmol. The Krafft point, emulsification, and foaming power of these surfactants were investigated as well. The Krafft points were 0°C (CC-G), 5°C (CC-T) and 20°C (CC-T). For CC-G, the separation time of 10 mL double distilled water (DDW) was 43 min, CC-T 40 min, and CC-L 37 min. It was inferred from the calculated packing parameters that shape of the micelle of CC-G, CC-T were cylindrical in aqueous media, while CC-L was spheroidal in aqueous media.