Study On The Preparation Of Porous Calcium Alginate Microspherers Via Emulsion Templating Method

Emulsion templating technique is a newly developed method for producing highly monodispersed porous materials. Most of its applications focused on the fabrication of inorganic porous materials. Little study was directed to form porous materials based on natural polymers via emulsion templating technique.Sodium alginate derived from brown sea algae is an anionic linear polysaccharide. It is biocompatible, biodegradable and relatively economical, and has been much used in biomedical field in recent years.In this thesis, the preparation of calcium alginate microspheres through inverse suspension-crosslinking method, the parameter choosing of emulsion templating system, the state of templates in alginate gels and the morphology of the obtained materials were investigated in detail. The emulsion and calcium alginate gels were characterized by surface tension test, particle size and size distribution test, optical microscope and SEM, etc.The results showed that the relative amount of dispersing medium, the concentration of sodium alginate solution, the stirring rate, the dispersant and its quantity were all the factors influencing the preparation of alginate microspheres by inverse suspension-crosslinking method. The volume ratio of dispersing medium to dispersed phase should not be less than 2:1. The concentration of sodium alginate solution should be controlled in the range of 2%－3.5%. Stirring rate between 300r/min and 450r/min was necessary for good spherical particles. Using suitable quantity of Span85&Span80 and PVP as dispersants could lead to microspheres with uniform size.The emulsion surface tension tests showed that for a relatively stable emulsion based on liquid paraffin, Span85&Tween60 and sodium alginate solution, the optimal HLB, the content of surfactants were 12.3, 70－110% respectively, and the proper emulsification time was about 60min. The observation of templates in alginate gels indicated that toluene and 1-dodecanol were not the right candidates as dispersed phase of the emulsion templating system, while liquid paraffin was the selected template. Size and distribution of liquid paraffin droplets in the prepared gels could be controlled precisely by adjusting the amount of surfactants and template. The SEM photographs of dried alginate gels showed that there were monosized pores in the final products.