Research On The Synthesis And Properties Of Silk Peptide-based Surfactant

Silk fibroin is natural protein, it has eighteen kinds of amino acid. The silk peptide with small molecule which is hydrolysised from silk fibroin can dissolve in the water. The silk peptide-based surfactant synthesized by silk peptide is in accordance with the requirements of eco-surfactant, which has good biodegradable and security.In this paper, silk peptide-based surfactants were synthesized from silk amino, silk peptide with molecular weight 2000-3000, which was hydrolysised from silk fibroin, and fatty acyl chloride using Schotten-Baumana method. By the study of the optimum conditions of synthesizing the sodium lauroyl silk amino, the optimum conditions of silk peptide-based surfactants were obtained as follow:mixed solvent of water-acetone, the volume ratio of water:acetone was 3 : 7, the molar ratio of silk peptide:fatty acyl chloride was 2:1,pH was 9, reaction temperature was 25℃, reaction time was 4h. Under these conditions, the yield of sodium lauroyl silk amino was 66.54%. The structure of sodium lauroyl silk amino, sodium lauroyl silk peptide was characterized by IR. The character of sodium lauroyl silk amino synthesized from different conditions were studied by amino acid analysis. The amino acid analysis indicated that there were many kinds of amino acid in the products, and the most ones were glycine and alanine, which makes up nearly 95% of the total content of amino acid.The wetting, emulsing, dispersing and foaming properties of compound system were tested in this paper. The results showed that this kind of surfactant had excellent wettability, bad emulsification to polar and low polar polymer, better emulsification to non-polar polymer, and good dispersion. The silk peptide based-surfactants had excellent foaming ability and foam stability. Non-ionic polymer could affect the foaming property.In this paper, the interaction between silk peptide-based surfactants and inorganic salts, polarity of organic dodecanol, water-soluble polymer and non-ionic surfactant AEO-9, were investigated by means of surface tension. The results showed that inorganic salts NaCl, Na2SO4 could improve the surface tension of SFJ-12 and cut down the cmc. The interaction between SFT-12 and inorganic salts were not obvious, but the surface tension had a falling trend. The effects of high molecule polymer to SFT-12 were relatively weak, but there was molecules adsorption at a lower concentration of surfactant, which indicated that there was a certain synergy between the high molecule polymer and surfactant. With a very small concentration of non-ionic surfactant AEO-9, the surface tension of SFJ-12 and SFT-12 could decrease significantly. The affect of dodecanol to SFJ-12 and SFT-12 was obvious. The surface tension of the solution could be reduced to very low by adding appropriate amount of dodecanol.