Stabilizing High Internal Emulsions And Application Of Cellulose Nanocrystals

Emulsions with a large volume of dispersed phase and stabilized by solid particles are termed as Pickering high internal phase emulsions(HIPEs),have been widely used in food,cosmetic,pharmaceutical and other fields.However,most of the literature dealing with Pickering stabilization concerns various types of inorganic or biological incompatible particles,which greatly restrict the application of emulsions.Therefore,it is very important to develop and utilize colloidal particles from biological sources as Pickering stabilizers.The present work investigated the fabrication and application of CNC-stabilized high internal phase emulsions.In addition,the emulsifying properties of CNC were improved by surface hydrophobicity modification.First,stable oil-in-water(O/W)Pickering(high internal phase)emulsions were formed using CNC as stabilizer and soy oil as dispersion phase via different homogenizing types.And the characteristics of formed emulsions were studied.The results showed that,increasing the energy input level of emulsification improved the emulsification efficiency,led to smaller particle size and better stability.Under high energy input(microfluidization),by modulating the particle concentration(0.3-1.2% w/v)and oil fraction(0.1-0.4 v/v),a kind of stable Pickering emulsions with tunable droplet sizes and rheological characteristics could be fabricated.If these emulsions were subjected to a centrifugation treatment(4000 g,5 min),concentrated and even gel-like fine Pickering emulsions(the oil fraction could be as high as 0.94 v/v)with relatively small particle size(0.22-12.96 ?m)and good stability could be produced.Next,the hydrophobic modification to CNC was carried out based on the acylation between the surface hydroxyl groups of CNC and anhydride from OSA,which was achieved through a convenient emulsifying-lyophilizing-heating treatment.The physicochemical and emulsifying properties of the modified CNC(OSA-CNC)were investigated.Results presented that,the degree of modification could be controlled by changing the reaction temperature(40-60?).After modification,the OSA-CNC nanoparticles with befitting surface hydrophobicity and integral crystal structure were obtained and could efficiently stabilize O/W HIPEs with smaller droplets,higher gel strength and store stability even at very low particle concentration.Finally,a novel porous material was fabricated based on the emulsions encapsulating cyclohexane stabilized by OSA-CNC,through the freeze-drying technology.Consequences showed that,the final porous materials were directly obtained by removing the high content of volatile oil and low content of water from the precursor emulsions.The structure and related properties of the obtained porous materials were depended on the concentration of particles,the proportion of oil phase and the types of emulsification.And the porous materials all have high porosity and good oil absorption properties.In summary,CNC is biocompatible,easily to be modified,has unique nanostructure and intermediate wettability.It is not only an excellent stabilizer for emulsions,but also suitable for preparing porous materials.These findings are of great value and significance for the fabrication of new biocompatible Pickering(high internal phase)emulsions and porous materials,and expansing the applications of CNC in food,medicine,environmental protection and other fields.