Synthesis And Properties Of Aromatic Amino Acid Surfactants

Using phenylalanine and dodecyl chloride,tetradecyl chloride and hexadecyl chloride as raw materials,three sodium N-acylphenylalanine surfactants were obtained by Shawton Bowman condensation method?sodium N-lauroyl phenylalaninate,sodium N-myristoyl phenylalaninate,sodium N-palmitoyl phenylalaninate?.The optimal preparation process of two amino acid surfactants was obtained by single factor and orthogonal experiments.The structure of the product was analyzed by infrared spectroscopy?FT-IR?and nuclear magnetic resonance spectroscopy?¹H-NMR?.The surface activity,foam,emulsification and wetting properties were determined.Firstly,through the single factor experiment method,the effects of reaction time,reaction temperature,molar ratio of reactants and volume ratio of reaction solvent on yield of N-lauroyl phenylalanine and N-palmitoyl phenylalanine surfactants were investigated.;further through the four-factor three-level orthogonal experiment,the effects of the above conditions on the reaction yield were comprehensively investigated,and the optimal preparation conditions of each surfactant were obtained.The optimal preparation conditions of N-lauroyl phenylalanine surfactant are as follows:the reaction temperature 20?,the reaction time 5.5 h,and the molar ratio of the reactants n?lauroyl chloride?:n?phenylalanine?=1:1.4,the volume ratio of the reaction mixed solvent V?acetone?:V?water?=1.5:1,yield up to 86.7%.The preferred preparation conditions of N-palmitoyl phenylalanine surfactant are:reaction temperature 30?,reaction time 4 h,reactant charge molar ratio n?palmitoyl chloride?:n?phenylalanine?=1:1.2,the volume ratio of the reaction mixture solvent V?acetone?:V?water?=1.5:1,yield up to 93.5%.The surface tension of the three surfactants,foam properties,emulsifying properties,and wetting properties in the aqueous solution were tested.The experimental results show that as the hydrophobic chain length increases from 12 to 16,the critical micelle concentration?cmc?decreases from 0.15 mmol/L to 0.02 mmol/L,while?_cmc decreases from 34.56 mN/m to 31.52 mN/m,the wettability of the sheet deteriorated,and the emulsifying properties of soybean oil/water and liquid paraffin/water gradually increased.The foaming properties of the three sodium N-acyl phenylalanine surfactants increased first and then decreased with the increase of the hydrophobic chain,and the foam stability increased with the increase of the alkyl chain.