A Novel Bola-Type Rosin-Based Functional Surfactant and Its Synergistic Effect with Natural Surfactant Saponin

A novel bola-type acrylic-modified rosin ester tertiary ammonium salt surfactant (AETAS) with two hydrophilic groups and a rigid hydrophobic group was synthesized through a simple method from rosin acid, which is a natural raw material. The chemical structure of the synthesized surfactant was confirmed by infrared spectroscopy and nuclear magnetic resonance spectroscopy (1H NMR and 13C NMR). The critical micelle concentration (CMC) of the AETAS was 0.44 g/L, and the surface tension at the CMC (γ cmc) was 45.02 mN/m. Self-assembly behavior of the AETAS in aqueous solution was characterized by transmission electron microscopy. The micelle diameter of the AETAS was about 150 nm in aqueous solution. We also explored the synergy of the AETAS and soapnut saponin. The binary surfactant compound systems of the AETAS and soapnut saponin had obvious synergistic effect in enhancing surface activity when the mass ratio of AETAS/soapnut saponin was 1:1. The γ cmc of soapnut saponin was 47.70 mN/m when the concentration reached 0.46 g/L, but the γ cmc of mixtures decreased to 44.26 mN/m at 0.30 g/L. The emulsification ability of the mixtures was significantly improved and the emulsion performance increased from 245 to 595 s when the mass ratio of AETAS/soapnut saponin was 1:1.