Preparation Of Large-sized Mondispheresby Self-stabilized Precipitation Polymerization

Monodisperse polymer microspheres are widely used in the field of biomedicine,standard metrology and analytical chemistry,due to their advantages of small size,large specific surface area,and easy surface modification.Micron-sized monodisperse polymer microspheres are usually prepared by dispersion polymerization.However,dispersion polymerization requires the addition of a dispersant,which affects the purity of the product and is difficult to be removed from the product.In order to overcome the shortcomings of dispersion polymerization,self-stabilized precipitation polymerization was utilized to prepare monodisperse micron-sized copolymer microspheres with particle size in the range of 1?6 ?m by adjusting the monomer concentration and solvent composition.The effects of monomer ratio and concentration,solvent composition and monomer feeding mode on the morphology and particle size were studied.The reaction condition was optimized for the preparation of large-sized monodisperse polymerized microspheres.The specific research contents are as follows:1.Preparation of a-methylstyrene(AMS)-styrene(St)-maleic anhydride(MAH)copolymer.The effect of monomer ratio and concentration,solvent composition,and initiator dosage on the particle size and particle size distribution was studied.The results indicate that with the increase of AMS component,the particle size increased firstly and then decreased.When[AMS]:[St]:[MAH]=5:5:10,the particle size was the biggest.The size of the particles gradually became bigger with increasing monomer concentration,but the particle size distribution became wider when[MAH]>2.0 mol/L.Monodisperse microspheres with a diameter of 2130 nm were successfully prepared when[MAH]=2.0 mol/L,[AIBN]=0.02 mol/L,[AMS]:[St]:[MAH]=5:5:10.For the two-step method,the effect of monomer feeding mode and feed ratio on the particle size was investigated.The results showed that the particle size was more uniform when the monomer was added dropwisely in the second step.When the monomer feed ratio was less than 1:2(mass),monodisperse microspheres of 2040 nm were prepared.2.p-tert-Butyl styrene(tBS),p-chloromethyl styrene(p-CMS),p-methoxy styrene(p-MOS),p-chlorostyrene(p-CS)were selected as the styrene derivative.The influences of the polarity of the substituent and the solvent composition on the particle size were investigated.With tBS as the monomer,[AMS]:[tBS]:[MAH]=1:9:10,[MAH]=2.0 mol/L,[AIBN]=0.02 mol/L,isoamyl acetate/n-heptane equal 5:5(V/V)as solvent,the resultant monodisperse microspheres have a diameter of 2805 nm.3.C8-MAH copolymer microspheres with big size were synthesized directly using the C8 fraction and MAH.The effects of monomer concentration,crosslinker type and concentration on the particle size were investigated.The results showed that the particle size increased with the increase of monomer concentration.The particle size was 5660 nm and the polydispersity index was 1.04 when the monomer concentration was 29%,.However,the particle size distribution became broadened when the monomer concentration was higher than 29%.Monodisperse crosslinked copolymer microspheres with a diameter of 5270 nm and a polydispersity index of 1.03 were successfully prepared with divinylbenzene as the crosslinking agent,28%monomer concentration,and the crosslinking agent dosage was 2%.