Investigation On The Nanoparticles Modified By Sodium Conjugated Linoleate And Their Application

Conjugated linoleic acid?CLA?,a natural unsaturated fatty acid,is pH responsive due to existence of the carboxyl group and has strong crosslinking activity endued by the conjugated double bonds.Because of their special surface physical and chemical properties,nanoparticles are widely applied in cosmetics,medicine and other fields.In this paper,SiO₂ and CaCO₃nanoparticles are employed as model nanoparticles and sodium conjugated linolenate?SCL?is induced to form monolayer or bilayer molecular membranes on the surface of nanoparticles.Subsquently,the SCL molecular membranes are chemically tethered to achieve the surface modification of nanoparticles.Moreover,the emulsifying properties of modified nanoparticles are studied and the pH/CO₂ double responsive Pickering emulsion is obtained.Compared to conventional emulsions,Pickering emulsions stabilized with nanoparticles as particulate emulsifiers have better performance in terms of stability and safety.Therefore,they are often used to prepare emulsions instead of small-molecule emulsifiers.However,the characteristics of nanoparticles that are too hydrophilic and easily agglomerate into clusters limit their applications to a certain extent.In view of this problem,the nanoparticles need to be surface-modified during application.So far,there have been few reports on SiO₂nanoparticles that have negatively charged surfaces modified with fatty acids.Nanoparticles have been surface-modified by esterification or hydrogen bonding in related reports.The former makes the fatty acid lose p H responsive of the carboxyl group during application,while the latter cannot avoid the desorption of the fatty acid in the application.Therefore,it is hypothesised that fatty acids can be induced and positively adsorbed on the surface of the SiO₂ nanoparticles,at the same time the fatty acids are stable.On the other hand,CaCO₃nanoparticles with positive surface charges may induce SCL to form"vesicles"on the surface of particles through electrostatic interactions and hydrophobic forces between SCL molecules,but this"vesicle"structure is easily damaged by other forces.On the other hand,fatty acid vesicles are mostly prepared by mechanical or self-assembling methods,but the mechanically prepared fatty acid vesicles are unstable and the sizes of the vesicles are limited by self-assembly.About all,the second assumption proposed is whether nanoparticle used as a harding template could induce the formation of vesicles or other new structures,and explore its emulsifying properties.Aiming at the aforementioned two concerns,this disseration mainly focuses on the following:?1?In the condition of pH 9.6,SCL molecules were induced to form a forward adsorbed monolayer on the surface of SiO₂ nanoparticles and self-crosslinking of the SCL molecules on the surface of particles was performed by heating to construct SiO₂ nanoparticles with a stable monolayer structure on the surface?SCL@SiO₂?.Compared with the simply SCL-adsorbed SiO₂ nanoparticles,it was found that the modified nanoparticles after heat-curing had significantly better thermal stability and this particles had pH-responsive.The emulsification properties of SCL@SiO₂ nanoparticles were investigated.It was observed that a mass fraction of 0.25 wt%emulsifier could stabilize the liquid paraffin with a volume fraction of 0.75 and the emulsion had a double pH/CO₂ responsive.Meantime,it was found that the particle sizes of the emulsion droplets stabilized by SCL@SiO₂ nanoparticles increased with the increase of SiO₂ nanoparticles sizes.?2?CaCO₃ nanoparticles could induce SCL molecules to form a surface double-layer structure at pH 7,and SCL molecules were self-crosslinked by thermal polymerization to form CaCO₃ nanoparticles?SCL@CaCO₃?with a stable polymeric vesicle structure on the surface.There was an discussion about the emulsifying properties of SCL@CaCO₃nanoparticles as emulsifiers,it revesled that adding Ca²⁺could adjust the hydrophilicity and hydrophobicity of the surface of SCL@CaCO₃ nanoparticles.And Pickering emulsion stabilized with SCL@CaCO₃ nanoparticles could make the catastrophic phase inversion when a certain concentration of Ca²⁺were added.?3?CaCO₃ nanoparticles as a hard template could induce the formation of vesicles on its surface through the method described in?2?,and then inducible vesicles could form by remove the template using EDTA chelation,which provided a new idea for the preparation of vesicles.In addition,Janus nanoparticles with SCL bilayer on the partial surface of CaCO₃nanoparticles were prepared by Pickering emulsion templating method.The results showed that the Janus particles and Pickering emulsion stabilized by Janus had pH-responsive.And stimuli-responsive Pickering emulsion was successfully prepared by pH-responsive inorganic Janus nanoparticles.