Preparation And Engineering Study On Particle Size Control Of Polystyrene Microspheres

Nowadays, the polymer microspheres with their surface grafted by active groups such as carboxyl, amidogen and hydroxyl could easily react with enzyme, protein, nucleic acid have been widely used into various application fields of biology, chemistry, materials science, medical science, which have attracted increasing research interest. Therefore, in this thesis, focusing on fabricating mono-dispersed polystyrene microspheres with controllable particle sizes, dispersion polymerization and soap-free emulsion polymerization have been used and the influences of various experimental processing parameters on both particle sizes and size distuributions of the synthesized microspheres have been systematically investigated. Moreover, several routes have been developed to accomplish the surface functionalization of the microspheres. Based on these, the preparing technique has been optimized and scaled up to production batch sizes. The involved research work and main conclusions are as follows:1. Polystyrene microsphere prepared by dispersion polymerizationThe polystyrene microspheres with submicron particle sizes or micron particle sizes have been synthesized by dispersion polymerization with styrene as monomer, azodiisobutyronitrile as the initiator, poly(vinyl pyrrolidone) as the dispersant, the mixture of absolute ethyl alcohol and deionized water as the dispersing medium. The particle morphologies and particle sizes as well as their particle distributions of the obtained polystyrene microspheres was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, dynamic light scattering, laser particle sizes distribution instrument etc. The results indicated that the particle sizes of the as-synthesized microspheres with smooth surfaces and fine sphericities could be well-controlled in the range of200to500nm. Both their particle sizes and size distributions could adjusted by altering the starting recipes. The shperes grew up as the content of the initiator, the content of the monomer or the ratio of the ethyl alcohol in the dispersing medium increased. The microspheres could approach fine solventresistance after being cross-linked.2. Carboxylic polystyrene microspheres fabricated by soap-free emulsion polymerizationThe carboxylic polystyrene spheres have been fabricated by soap-free emulsion polymerization with styrene and acrylic as the initiator, potassium peroxodisulfate as the initiator, deionized water as the dispersing medium. The results from transmission electron microscopy as and dynamic light scattering demonstrated that the particle size of the prepared microspheres was uniform and the particle sizes could be controlled in the range of150to400nm by altering the ratios of the acrylic as the copolymerization, the contents of the initiator, polymerization temperatures and stirring rates. The contents of the carboxyl groups could reach a high value of0.135mmol/g, which could satisfy the pratical applications in microsphere array chips.3. Engineering researchThe prossing technique was scaled-up to production batch sizes of2L based on optimizing the processing parameters. The problems such as the poly-disperse and agglomeration of the obtained shperes in factory was sovled. The carboxylic polystyrene microspheres with particle sizes of900±40nm, carboxylic polystyrene microspheres with particle sizes of350±10nm, and polystyrene microsphere with particle sizes of1200±50nm have been successfully produced with stable precossing technique. The operation instruction has been established for continuous production in factory.