Fabrication Of Mono-dispersed Magnetic Polymer Microspheres And Surface Modification By Hydrophilic Polymers

With the development of the technique in preparation of polymer latex,the applications of latex and microspheres have been broadened from earlier industry field such as coatings,papers,adhesive,plastic additives and architecture materials to biomedical and biochemical fields.Polymer microspheres were usually prepared by emulsion polymerization,but when the polymer micrsopheres directly prepared by emulsion polymerization can not be satisfied with the requirment,surface modification of the as-prepared microspheres was necessary to prepare functional polymer micropheres.In this thesis,we prepared three kinds of multifunctional polymer microspheres:(1) We prepared different-sized P(MMA-GMA-DVB) (PMGD)micropsheres modified by dendritic PAMAM(d-PAMAM) at first,and then red fluorescent microspheres were achieved by attachment of TRITC to the surface of microspheres;(2) The magnetic microspheres modified by d-PAMAM were prepared, and then FITC was attached to give the micropsheres fluorescent property;(3) The microspheres modified by polyasparagine derivatives were prepared to enhance the biocompatibility.The results of each part were listed as follows:(1) Mono-dispersed PMGD microspheres with size ranging from 200 to 800 nm were synthesized by soap-free emulsion polymerization and seeded polymerization. The as-prepared microspheres were aminated by ethylenediamine.Afterwards, different generations of d-PAMAM were grafted onto the surface of the microspheres by repeated Michael additions and amination reactions,at last different-sized water-dispersible microspheres with red fluorescence could be prepared by covalently coupling tetramethyl rhodamine isothiocyanate(TRITC).(2) Different kinds of magnetic fluids were firstly prepared through changing the content of oleic acid and ammonia solution to disperse the monolayer-oleic acid-stabilized magnetite particles.Then magnetic polymer microspheres were prepared by soap-free emulsion copolymerization of methyl methacrylate and divinylbenzene in the presence of above magnetic fluids.The effects of various polymerization parameters such as the content of oleic acid,ammonia solution in the dispersion solution and the content of divinylbenzene on the morphology and size of the magnetic microspheres were investigated in detail.The magnetic functional microspheres were obtained by seeded emulsion polymerization of 2-Hydroxyethyl methacrylate(HEMA),tert-butyl methacrylate(t-BMA),N-isopropylacrylamide (NIPAM),glycidyl methacrylate(GMA) and styrene(St) using the Fe₃O₄@P(MMA-DVB) microspheres as seeds.At last,multifunctional microspheres with superparamagnetic,pH-sensitive,and photoluminescence properties were achieved by the following procedure:(a) the chemical modification of the PMGD shells with ethylenediamine(EDA) to yield amino groups;(b) the dendritic poly(amidoamine)(PAMAM) shells were coated on the magnetic particles on the basis of the Michael addition of methyl acrylate and amidation of the resulting ester with large excesses of EDA,which could achieve generational growth under such uniform stepwise reactions;(c)(FITC),which is a popular organic dye,was reacted with the terminal -NH2 groups from the dendritic PAMAM shells(3) Mono-dispersed PMGD microspheres were prepared by soap-free emulsion polymerization and polysuccinimide(PSI) were prepared by polycondensation of L-aspartic acid(L-ASP) using phosphoric acid as a catalyst in sulfolane/mesitylene. Then,PSI was attached to the surface of PMGD microspheres in N,N-dimethylformamide(DMF) and deionized water,respectively.(a) Grafting in DMF solution:PMGD microspheres with different content of DVB were prepared first and then was aminated by EDA,then PSI was attached to the surface of PMGD microspheres through the reaction between the amino groups of mcirospheres and highly chemical reactive loops of PSI;(b) Grafting in water:PMGD microspheres with 10 wt%of DVB were prepared at first,then these microspheres were aminated by EDA,finally,the PMGD microspheres modified by polyasparagine derivatives were achieved.Element analysis was used to characterize the finial microspheres.