Study Of Synthesis And Surface Properties Of Glucose-based Amino Acid Dimer Surfactants

Carbohydrate compounds, due to their special hydrophilic structure of many hydroxyl groups, through some corresponding modification to connect with the hydrophobic chain of long carbon chain, a class of glucose-based surfactants will be obtained. These kinds of surfactants are widely used in food, cosmetics, medicine and other industries due to their nature, safety, avirulence, good chemical stability and so on.The traditional surfactants are made up of single hydrophilic head group and single hydrophobic chain, due to their molecular structures, there are many restrictions on performance improvements. Gemini surfactants, which contain two hydrophilic head groups and two hydrophobic chains are too strong in hydrophilicity performance. It is difficult to form a stable oil-in-water emulsion, and therefore can not well reduce the interfacial tension between oil and water. In order to adjust the hydrophilic lipophilic balance, the main contents of this paper is the synthesis of a class of AOT surfactants with two hydrophobic chains and single hydrophilic head group and Bola surfactants with two hydrophilic head groups and single hydrophobic chain.In this dissertation,4 kinds of lysine glucose ester dimer surfactants with two hydrophobic chains and 4 kinds of glutamic acid glucose ester compounds with two hydrophilic head groups were synthesized using L-lysine, L-glutamic acid, alpha-D-Methylglucoside as row materials. The target products were synthesized by Schotten-Baumann condensation, benzyl protection, Steglich esterification and Pd/C debenzylation. IR、1HNMR、ESI-MS spectra were used to confirm the chemical structures of the intermediates and the target products. The reaction conditions of each steps were optimized:(1) synthesis of N-acyl amino acids:the ratio of L-lysine and fatty acyl chloride 3:4, the volume ratio of acetone and water as solvent 2:1, reaction temperature 0-5℃, pH 10, reaction time 4h, to the yield 71.7%; (2) benzyl protection of alpha-D-Methylglucoside:the ratio of NaH, alpha-D-Methylglucoside and benzyl bromide 5.5:1:5, DMF as solvent, reaction temperature 40℃, reaction time 24h. Demethylation:the ratio of glacial acetic acid and 10% hydrochloric acid 1:1, reaction temperature 90℃, reaction time 12h, to the yield 44.6%; (3) Steglich esterification:the ratio of EDC1 and N-acyl amino acid 1.5:1, the ratio of N-acyl amino acid and 2,3,4,6-Tetra-O-benzyl-D-glucopyranose 1.5:1, DMAP as catalyst in an amount of 40% mass of glucose, reaction temperature 30℃, reaction time 24h, to the yield 91.2%; (4) Pd/C debenzylation:the volume ratio of ethyl alcohol absolute and dichloromethane as solvent 1:1,5% Pd/C as catalyst in an amount of 20% mass of reactants, reaction temperature 30℃, reaction time 48h, to the yield 46.7%.The surface tension(y) of the synthesized dimer surfactants were determined by drop volime method, The results show that the surface tension and critical micelle concentration(cmc) of the lysine glucose ester surfactants gradually decreased when the length of the carbon chain increased from 8 to 10, but increased when the length of the carbon chain increased from 10 to 14. Thus the critical micelle concentration of the lysine glucose ester surfactants is not only related with the length of carbon chain, and is also linked to the steric hindrance effect of the double carbon chain. The surface tension and critical micelle concentration of the glutamic glucose ester surfactants with two hydrophilic head groups were consistent with general rules of surfactants:with the lengthening of hydrophobic chain, the efficiency of reducing surface tension increased and cmc decreased.