Research On The Assembly Mechanism And Application Of Alginate-based Submicrogel Particles At The Oil-water Interface

Emulsions stabilized by solid particles instead of traditional emulsifier were called Pickering emulsions.Compared with traditional emulsions,Pickering emulsions have some advantages,such as nontoxicity,stability,less foam,and so on.Therefore,Pickering emulsions can provide important values in the field of food,medicine,cosmetics,petroleum and wastewater treatment.Sodium alginate(Na-Alg)is a kind of natural polysaccharide with the properties of nontoxicity,good bio compatibility and biodegradability.In this article,Na-Alg was used to develop amphiphilic alginate-based submicron gel particles.The assembly mechanism of gel particles at oil-water interface was researched,and the amphphilic gel particles were used in cosmetics.The specific methods,contents and results are as follows:Calcium alginate(Ca-Alg)submicron gel particles were gotten through precipitation transfer method.The gel particles were characterized by dynamic light scattering(DLS),scanning electron microscope(SEM),transmission electron microscope(TEM),freeze fracture transmission electron microscope(FFTEM).By adjusting the concentration of Na-Alg,the content of CaHPO4,the dropping rate of CaHPO4 and the preparation temperature,the particle size of Ca-Alg can be controlled in submicron level.Octyl amine was used to modify Ca-Alg gelparticles to provide amphiphilic alginate amidation derivatives(Ca-alg-C8)with different grafting ratio(8.8%,19.7%and 38.9%),using 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride(EDC-HCI)as a coupling agent.The particle size,distribution and morphology of Ca-alg-C8 were characterized by DLS,SEM and TEM.The results show that Ca-Alg and Ca-alg-C8 particles have a regular spherical morphology both in wet and dry condition.And the particle size in dry condition was much smaller than that in wet condition.The surface tension and interface tension of Ca-alg-C8 with different substitution degree and concentration were determinate.As a result,surface tension and interface tension both decrease with the increase of particle substitution degree and concentration.The contact angle of Ca-alg-C8 particle membrane,oil and water phases was measured by optical contact angle measuring device.The study found that with the substitution degree of Ca-alg-C8 increase,the contact angle increases,and the Ca-alg-C8 particles become more hydrophobic.The zeta potential of gel particle suspension was measured and the result showed that zeta potential ofNa-alg solution was higher than that of Ca-alg suspension.What's more,the zeta potential value decreases as the increase of substitution degree of Ca-alg-C8.The prepared Ca-alg-C8 gel particles were used to stabilize liquid paraffin/water emulsion.When the concentration of Ca-alg-C8 reaches 0.6%wt,the emulsion can be stabilized well.The particles with high substitution degree tend to stabilize W/O emulsions,while particles with low substitution degree tend to stabilize O/W emulsions.The volume fraction of oil phase affects the stability and the type of the emulsions.When the oil-water ratio increased from 1:1 to 2:1,the O/W emulsions turned into W/O emulsions.The confocal laser scanning microscopy(CLSM)pictures of the emulsions proved that amphiphilic Ca-alg-Cs gel particles were adsorbed to the oil-water interface and prevented the coalescence of the droplet,which confirmed the adsorption mechanism of the amphiphilic gel particles at oil-water interface.The Ca-alg-C8 gel particles,the substitution degree of 19.8%,were used in cosmetic emulsion(cream,lotion)products.The results showed that the organoleptic quality of product meet the national standards for cousmetics.The stability of the products was studied through the cold resistant,heat resistant and centrifugal method.The results showed that the stability of the products stabilized by Ca-alg-C8 gel particles were comparable to that stabilized by traditional surfactant.What is more,the appearance of cream stabilized by Ca-alg-C8 gel particles was more exquisite.The microstructure of cosmetics was characterized by optical microscope.As a result,the cosmetic emulsion(cream,lotion)stabilized by Ca-alg-C8 gel particles possesses good heat and cold resistant abilities.Multiple Light Scattering technology further evidenced that the emulsion(cream,lotion)products stabilized by Ca-alg-C8 gel particles possess better stability than that stabilized by traditional surfactant.