Solution properties of cardanol-based anion-nonionic surfactant and application in emulsion polymerization

Abstract Using cardanol-based nonionic surfactant, cardanol polyoxyethylene ether (NSF) with an EO addition number of 7 as the precursor, the anionic-nonionic surfactant, cardanol polyoxyethylene sulfate (NES) was prepared via sulfonation with chlorosulfonic acid. The molecular structures were characterized by FT-IR, and the solution properties were conducted and compared with NSF. The results indicate that the introduction of anionic groups significantly improves the water solubility, resulting in a low Krafft point (<0 °C). Compared to NSF, NES solution exhibits superior high-temperature stability, as well as higher resistance to alkali and salt, meeting the requirements for applications under high-temperature and high-salinity conditions. Surface tension tests demonstrate that NES possesses stronger hydrophilicity, with a looser molecular arrangement at the interface (larger molecular cross-sectional area), leading to the reduction in the ability to reduce surface tension (larger γ cmc ) and efficiency (smaller pC 20 ). While both the diffusion barrier from bulk to subsurface and the adsorption barrier from subsurface to interface increase. NES shows more prominent emulsification stability for polar soybean oil and foam stabilization capability, and is demonstrated to be a green bio-based emulsifier for acrylate emulsion polymerization, with high monomer conversion rate of 97.35 %, small particle size and narrow distribution.