Effect Of Surfactant On The Properties Of Pickering Emulsion Stabilized By HAP Nanoparticles And The Structure Of Cured Material

Biological porous scaffolds have great application value in drug delivery,tissue engineering scaffolds,adsorption,catalysis and many other fields due to their characteristics of three-dimensional network structure,high porosity,large specific surface area,excellent biocompatibility,etc.Emulsion template method can be used to prepare porous scaffold materials with regular structure and controllable pore size.Both solid particles and surfactants can be used as stabilizers to prepare emulsion,in which the emulsion stabilized by solid particles is called Pickering emulsion and the emulsion stabilized by surfactants is called traditional emulsion.The emulsion system coexisted with these two kinds of emulsifiers have more excellent properties,and can prepare porous scaffold materials with controllable pore structure and adjustable porosity.Different types of surfactants were added to the Pickering emulsion prepared using hydroxyapatite（HAp）as stabilizers,in which poly（L-lactic acid）was dissolved in dichloromethane（CH₂Cl₂）solution as oil phase and HAp nanoparticles were dispersed in distilled water as aqueous phase in this work.The influence of different types of surfactant on the properties of Pickering emulsion stabilized by HAp was studied.For the emulsion containing nonionic surfactant Span 80,influence of different preparation parameters on emulsion properties（type,stability,droplet size and distribution,HAp adsorption behavior）and microstructure of cured materials were investigated by changing the concentration of surfactant,emulsification time,emulsification rate,the concentration of PLLA and the surface chemical property of HAp.The influence mechanism of Span 80 on Pickering emulsion stabilized by HAp was revealed.For the emulsion containing ionic surfactant CTAB or sodium oleate,effect of the addition of surfactant in different concentration on the stability of HAp aqueous phase,Zeta potential of HAp,HAp particle size,interfacial tension and the type,stability,droplet size and distribution of Pickering emulsion were studied.The influence mechanism of ionic surfactants on Pickering emulsion stabilized by HAp was also analyzed.The results indicated that for the emulsion containing Span 80,emulsion type changed from O/W to W/O with the increase of the Span 80 concentration.Emulsion stability increased first and then decreased with the increase of the Span 80 concentration.The change of preparation parameters such as emulsification time,emulsification rate and the concentration of PLLA in the oil phase could affect the performance of emulsions.The synergistic effect between HAp and Span 80 could be further increased by introducing hydrophobic CH2 groups onto the surface of HAp.SEM results showed that moderate concentration of Span 80,an increase in emulsification time or emulsification rate and hydrophobic modification of HAp could improve the porosity of the cured open-cell materials.There was double phase inv ersion occurred with the increase of CTAB concentration for the emulsion system containing CTAB.Emulsion stability decreased first then increased and then decreased with the increase of CTAB concentration.SEM results showed that the prepared porous materials had a interconnected structure but the pore walls were very thin.For the emulsion system containing sodium oleate,emulsions also underwent double phase inversion with the increase of sodium oleate concentration.But emulsion stability tended to increase first and then decrease with the increase of sodium oleate concentration.The pore structure of porous materials after curing was not uniform and with relatively low connectivity.