Synthesis And Properties Of Fatty Acylethyl Betaines

A series of novel betaine surfactants containing ester bonds were synthesized through reactions between sodium chloroacetate and the intermediate fatty acylethyl dimethyl tertiary amine, which was prepared using fatty acid (lauric acid, myristic acid, palmistic acid) and N,N-dimethyl ethanolamine as starting materials, p-toluenesulfonic acid as catalyst. In this paper, the best reaction conditions for the two-step preparation of this series of fatty acylethyl betaines were investigated using orthogonal experimental design method, while establishing products analysis methods both in quality and quantity. The surface chemical properties and hydrolytic properties of this series of products were also researched.In the process of synthesis the intermediate, took lauroylethyl dimethyl tertiary amine for example. Investigated the influence of such important parameters as materials/reactant ratio, solvents, reaction temperature and reaction time.Explored appropriate orthogonal test conditions, the optimum technological conditions were obtained via orthogonal experiments: N,N- dimethyl ethanolamine and lauric acid in a molar ratio of 1.6∶1, catalyst amount used 1.5%, reacted at 170℃for 12 h. The maximum yield was beyond 88%.The second step was to synthesis the final products, took the synthesis of lauroylethyl betaine for instance, with which the homogeneous experiment showed the optimum technological conditions were as follows: Isopropyl alcohol as solvent, the intermediate and sodium chloroacetate in a molar ratio of 1∶2.2, at 90℃for 21 h.The conversion rate was beyond 98%. Studied the best way to purify crude products, chose acetone to recrystal them. HPLC showed the purity of lauroylethyl betaine was beyond 99%. Its structure was characterized by FT-IR,ESI-MS and ¹HNMR spectrometry.Surface properties of this series of fatty acylethyl betaines were also studied, high surface activities were shown: The cmc(critical micelle concentration) of lauroylethyl betaine, myristoylethyl betaine and palmitoylethyl betaine were 5.13×10^-4 mol·L^-1, 2.63×10^-4 mol·L^-1, 2.63×10^-4 mol·L^-1 each.γcmc were 28.09 mN·m^-1, 30.56 mN·m^-1, 41.16 mN·m^-1 each. This series of fatty acylethyl betaines had better emulfication properties and wetting ability, stronger calcium soap scattered forces (LSDR) than BS-12 and SDS. They also showed excellent anti-hard water performance and low foaming property.The hydrolysis property of fatty acylethyl betaines was preliminary studied,hydrolysis performance of myristoylethyl betaine was discussed, analysis results showed that: Myristoylethyl betaine had good chemical hydrolysis property; Meanwhile, it was stable enough in normal temperature, pH relatively moderate using conditions.Therefore, it showed brilliant application potential.