Self-assembled structures and excellent surface properties of a novel anionic phosphate diester surfactant derived from natural rosin acids

Abstract

A novel anionic rosin-based phosphate diester sodium (DDPDS) was successfully synthesized from raw dehydroabietic acid, a natural raw material, via four-step reactions: acylation, esterification, phosphorylation and neutralization. Nuclear magnetic resonance (13C NMR) and Fourier transform infrared spectroscopy (FT-IR) were used to characterize the structure of target products. The aggregation behaviors in aqueous-ethanol solution and surface properties of DDPDS and its mixed systems were investigated by transmission electron microscopy (TEM), automatic tensiometer and contact angle measuring instrument. The results showed that DDPDS had high surface activity, unexpected emulsification and excellent wettability. The critical micelle concentration (CMC) of 1.35g∗L−1, the minimum surface tension (γcmc) of 31.75mN∗m−1, emulsifying power of 153s and the minimum contact angle of 13.4° were determined for DDPDS. Spherical vesicles with diameter about 50nm and 5μm were self-assembled respectively in aqueous-ethanol solution when DDPDS concentration is about 1 CMC and 5 CMC. Two surfactant ionic self-assembly systems were constructed by mixing DDPDS with sodium dodecylbenzenesulfonate (SDBS) and cetyltrimethylammonium bromide (CTAB), which forms 40nm and 20nm spherical micelles in 1 CMC aqueous-ethanol solution. Possible formation mechanisms of surfactant ionic self-assembly systems on a combination of ionic interactions between DDPDS and SDBS or CTAB are discussed. It was found that there were an obvious synergistic effect of foam stability in DDPDS/SDBS mixed system and an obvious synergistic effect of foam capability in DDPDS/CTAB mixed system.