Study On The Properties Of Green Soft Matter Systems Based On Sodium Lauroylglutamate

In recent years,soft matter systems such as foam,film and so on,have been widely used in the industrial production of biomedicine,cosmetics,food and other industries.Designing green functional systems with the characteristic of non-toxic,biological compatibility and high biodegradability is the development goal of soft matter systems,and also one of the current research hotspots.The amphiphilic property and strong compatibility of surfactants make it possible to be used to assemble soft matter.The construction of soft matter systems based on green surfactants and other green additives has the important theoretical significance and application value.In this paper,amino-derived surfactant sodium lauroylglutamate(LGS)was chosen as the main research object.Several kind of green soft matter systems based on LGS,for example foam,thin film and hydrogel were designed by combining with other surfactants or natural polymers.The mechanisms of the influence of molecular behaviors of LGS on the properties of soft matter systems were explored.These discoveries would be helpful for proceeding the development and application of soft matter system based on LGS.This thesis mainly includes three parts:In the first part,the foam properties of binary mixtures of LGS interacting with different kinds of conventional surfactants were investigated.The additives were cationic surfactant dodecyl trimethyl ammonium bromide(DTAB),nonionic surfactant laurel alkanolamide(LAA)and anionic surfactant sodium dodecyl sulfonate(SDS),respectively.The effect of interfacial molecular arrangement behavior on foam properties of the binary-mixed systems was explored.The effects of pH,concentration and hydrophobic chain length of surfactant on the properties of the foam systems were also investigated.The results showed that the three binary-mixed systems all had obviously synergism effect on foaming which showed the strongly compatibleness of LGS,and the order of synergistic effect was DTAB>LAA>SDS.The surface tension and foam drainage process of the mixed systems were characterized by experimental methods.The interfacial molecular array behaviors of surfactant at the air/water interface was analyzed by computer simulation at the molecular level.By combining the experimental results with simulation results,the mechanism that the foam properties of LGS were improved by DTAB,LAA and SDS was revealed.In the second part,the foam properties of mixtures of LGS interacting with natural polymer such as hyaluronic acid,keratin,and elastase were investigated.The results showed that the foam properties of LGS was slightly improved by hyaluronic acid due to the weaker molecular interaction between LGS and hyaluronic acid.The foam properties of LGS were significantly reduced by elastase because of the strong interaction between elastase and LGS in the bulk phase.While the LGS/keratin complex systems showed obvious synergism effect on foam properties in the specific ratio range.By exploring the effect of concentration and pH on the foam properties of LGS/keratin system,it was found that when LGS concentration was lower,the long chain of keratin could provide more active sites for LGS,which increased the amount of interfacial adsorption and surface activity of LGS,and thereby improved effectively the foam performance.When the concentration of LGS was higher,the presence of polypeptide chains of keratin was beneficial to the micellization of LGS,so the molecules at surface were mainly LGS for keratin/LGS system,and the foam properties of the compound system are not significantly enhanced compared with LGS.Meanwhile,the existence of keratin reduced the sensitivity of LGS system on pH,and the LGS/keratin system had good foam properties in wider pH range than pure LGS systems.It was found that the mechanisms for keratin increased the foam performance of LGS systems under alkaline and acidic conditions were different.In the third part,the possibility to prepare green water soluble film and hydrogel by LGS/keratin system was explored.The preparation of LGS/keratin composite films was mainly investigated and the mechanism was revealed.The results showed that keratin molecules can form thin film,but the mechanical properties of the formed film was very poor.While uniform elastic film could be prepared from LGS/keratin mixed solutions.By analyzing the micro structure of the samples by FT-IR and SEM,it was found that the interaction between LGS and keratin induced the variation of the secondary structure of keratin,which changed from a-helix to P-sheet,and network structure was formed due to electrostatic attraction and hydrophobic effect,which was also the reason that LGS improved the film-forming ability of keratin.Meanwhile,the?-sheet keratin increased the elasticity and elongation of the film with the existience of external force.The environmental conditions,such as temperature and pH influenced the performance of LGS/keratin composite films by affecting the intermolecular interactions.It was found that,when the experimental temperature was 60 ? and the solution was alkaline,the performance of LGS/keratin composite film was optimal.While the mixed solution of LGS/keratin can spontaneously assemble into hydrogel at room temperature at pH=3.