A Study Of Functional Monodisperse Polymer Microspheres

The development of multifunctional monodisperse polymer microspheres has been hampered by several problems, such as inhomogeneous size distribution, a lack of efficient purification methodology, weak performance in the application of biomedicine.Herein, we fabricate the monodisperse polystyrene microspheres via dispersion polymerization and seeded polymerization with a diameter range from 1 to 10μm. The functionalized microspheres were obtained by co-polymerization of styrene and co-monomers with functional groups. To clarify the size distribution relationship between the final fabricated beads (by seeded polymerization) and the initial seed particles (by dispersion polymerization), a theoretically investigation according to the principle of the ideal monomer absorption process was employed. And the size growth process was experimentally measured. In the meanwhile, the diameter and coefficient variation rates of the final fabricated beads to the initial seed particles were also investigated. Compared the measured size distribution with the estimated, it was found that the more homogeneous beads can be generated by selection of more uniform initial seed particles and meticulous adjusting synthesis parameters.A new, facile and milligram-scale method was developed to describe the motion of polymer beads in aqueous solution. The motion time (i.e. floating or sedimentation time) of beads in solutions is proportional to the viscosity of solutions. It is reverse proportional to the square of bead radius and the density difference between the beads and the solutions. The apparent density of monodisperse beads can be quickly and easily calculated using the motion time of polymer beads in glycerol aqueous solutions. The results indicated that the present method provided a more precise way to predict the movement of beads in aqueous solution compared with the approach for commercial use. Moreover, this method was developed to purify polymer beads from the reaction mixture containing larger beads, target beads and smaller second-nuclei beads. The efficacy equation was derived to predict the purification process.The magnetic nanoparticle-polymer hybrid microbeads were prepared by coupling blank polymer beads with magnetic Fe3O4 nanoparticles. A facile method, density selection method was introduced to isolate magnetic polymer beads from unattached nanoparticles based on their density difference. As the mixture of bead and nanoparticle was dispersed in 50 wt% glycerol solution, the lighter bead would float to the upper surface of medium, and the heavier nanoparticle had a tendency to settle towards the bottom of container. The bead could be efficiently collected due to the bead movement direction opposite to that of nanoparticles. The amounts of unremoved MNPs of purified beads were 35~55 % lower than those of beads by general centrifugation or external magnetic field separation methods.The fluorescent polystyrene beads were stained by gradual solvent evaporation method using dyes such as rhodamine 101 and acridine orange. Gradual solvent evaporation method facilitates a high concentration of fluorescent dyes on beads. This is the key to obtain fluorescent beads with high intensity. The results showed that the fabricated fluorescent microspheres could be excited to various wavelengths (such as yellow, green, red and scarlet). Our synthesized microspheres offer high fluorescence emission intensity compared to commercial fluorescent microspheres in the mean time have other properties in common.This study can be potentially employed in cell separation, microfluidics chip systems, early disease diagnosis, flow cytometry, suspension stability, and particle analysis systems.