Preparation Of Standard Material Of Nanoparticle

Monodisperse polymer microspheres are widely used in a variety of applicationssuch as the standard measurement, microscopic study, chromatography, cellmeasurement, organization separation technology, cancer cure and DNA technologybecause of their excellent properties such as small size, large surface area, strongabsorbility, the enrichment of functional groups in the surface and the ability of surfacereaction. Monodisperse polystyrene microspheres are widely used in colloid sciencebecause of their height of the single range, the ideal globular appearance, easily tocontrol the size of the particles and surface electric properties.Although dispersion polymerization attracted much attention and the researchliteratures of this aspect are very rich, but there are some defects in traditionaldispersion polymerization. As we known, the mechanism of dispersion polymerizationis typical living radical polymerization. Concentration of initiator will decrease alongwith the reaction leading to rate of living radical’s generation and system reactiondropping. For this, the ability of new living radicals to capture monomer will reducewith the number reducing so that the particles which have been synthesized in laterstage are smaller than the particles synthesized in early stage. Herein, a method ofcontinuous adding initiator is introduced to keep the rate of living radicals generationand system reaction. Monodisperse microspheres with clean surface can be prepared viathis new method.It is difficult to synthesize nanometer level polystyrene microspheres with uniformparticle size and clean surface by emulsion polymerization. And more the clean surfacein emulsion polymerization is the obstacle for purification and application ofpolystyrene. Herein we synthesize polystyrene microspheres with particle diameterunder100nm by emulsifier-free emulsion polymerization. Emulsifier-free emulsionpolymerization is on the basis of the development of traditional emulsionpolymerization which has a variety of advantage such as stable reaction and residue ofemulsifier. In this paper, we synthesize two kinds of polystyrene microspheres withparticle size90nm and50nm and which have high uniform particle size and cleansurface.At last we used field-flow fractionation technology to separate and refine thepolystyrene microspheres. The experimental result is except to the ideal results.