Preparation And Characterization Of Poly(Vinyl Alcohol)Microspheres

PVA microspheres were prepared via inverse suspension polymerization,using aqueous PVA solution as a dispersed phase(water phase),liquid paraffin,which containing Sorbitan monooleateas,as a continuous phase(oil phase),sodium trimetaphosphate as a crosslinker,and sodium hydroxide as a catalyst.Composition structure was characterized by Fourier Transform Infrared Spectrum(FT-IR)and Nuclear Magnetic Resonance(NMR).Morphology and particle size distribution of the microspheres were observed by the Scanning Electron Microscope(SEM),hydrophilic property was analyzed by Contact Angle Meter,and thermostability was analyzed by differential scanning calorimetry(DSC),phase structure was analyzed by X-Ray Diffractomer.And on this basis,we made An exploration to the contributing factors of being microspheres.The results showed that the process has obtained microspheres with good shape.A series of experiments were conducted to get the effects of polymerization parameters on particle size and size distribution.The results showed that the size of PVA microspheres would be influenced by monomer concentration,volume ratio of oil and water phase,crosslinking time,the speed of stiring,the amount of surfactant and the amount of STMP.There are a lot of hydroxyl groups on the surface of the microspheres;water can seep into the microspheres within Is,so the microspheres exhibit appreciable hydrophilicity;and endothermic peak area of microspheres is significantly lower than the raw materials in around 220?,so it has good thermal stability.The size distribution of the microspheres is a range from 1 to 20 ?m,and the average particle size is 11.5 ?m.Microspheres reach the equilibrium for 30 mintues in physiological saline,and the swelling ratio is 119.6%.What is more,STMP is nontoxic reagent,which can solve the problem of biocompatibility.It is concluded that the PVA microspheres are promising for drug sustained-release substrate.Using the method of inverse suspension polymerization can make the process simpler,and obtain microspheres with good shape.Because sodium trimetaphosphate is non-toxic agent,so using sodium trimetaphosphate as a crosslink agent can solve the problem of biocompatibility,therefore PVA microspheres are promising for drug sustained-release substrate.The microspheres,which gained by this process,can use as embolic agent.Compared with irregular particles,microspheres have some advantages:the specific surface area is small,not prone to the phenomenon of agglomeration;surface is smooth,less likely to absorb granules,reduce the miss embolism and complications caused by granules;not easily block blood vessel,and easier to fit on the inner wall of the cylinder of the vascular lumen.