(235f) Synthesis and Properties of p-(Lauryl)-Benzyl Polyoxyethylenate Ethers
The benzene ring in alkylphenol ethoxylates (APEO) provides smooth polar transition between hydrophobic alkyl chain and hydrophilic ethylene oxide (EO) chain, imparting emulsification, solubilization, wetting, penetration, dispersion, washing and other outstanding properties to these surfactants. APEO was originally widely used in the field of domestic, civil and industrial cleaning, and in the fine chemicals and polymer industry. It had a large annual consumption worldwide. In recent years, the poor biodegradability of APEO itself and the toxicity of its degradation products have caused widespread concern. European Union countries have banned the use of APEO, and China has also been restricting its application in many areas.
With the growth of environmental security awareness, an all-around ban of APEO will become an inevitable trend. Therefore, the development of a new surfactant molecule as the substitute of APEO is desired. A surfactant molecule that not only retains the benzene ring structure with excellent performance, but also avoids the phenol structure with poor biodegradability and reproductive toxicity, has great theoretical significance and broad market prospects.
In this paper, six kinds of para-lauryl-benzyl polyoxyethylenate ether (LBEOn) with different number, n, of ethylene oxide (EO) units (n = 4, 5, 7, 9, 11, or 13) were synthesized starting from dodecylbenzene by a three-step process including chloromethylation, hydroxylation and ethoxylation. Chemical structure of the LBEOn was characterized by FTIR and 1H NMR spectroscopy. Average EO mole adduct numbers in the LBEOn were characterized by ESI-MS. Critical micelle concentration (cmc) of the product was measured by surface tension method at 25 °C and other performance of applications of the products were also determined.
The experimental results showed that with an increasing number of EO in the surfactant, cloud points and wetting ability increased; cmc, emulsifying ability, and solubilization ability decreased when the EO mole adduct numbers equal to or greater than 9. Compared to the most commonly used alkylphenol ethoxylate, nonylphenol ethoxylate (trade name TX-10), the LBEOn with 9 EO has similar cloud point, cmc, and emulsifying and solubilizing power as TX-10. This LBEO may be an effective alternative to TX-10, with no concerns about environmental and reproductive toxicity.
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