Preparation And Application Of Monodisperse Microspheres Containing Dodecyl By Precipitation Polymerization

Luminescent polymer is a branch of photoelectric functional polymer.People have gained a lot of understanding of light-emitting polymers,because of their applications in organic light-emitting diodes,cell imaging and pathological detection,selective identification of ions and molecules,detection of pollutants and explosives and other fields and their inestimable potential,related research has been a hot spot in the scientific community.At present,when the fluorescence of polymer is used for the detection of target substances,the polymer is dissolved in the solvent to form a uniform solution.After the completion of the detection,the fluorescent polymer is difficult to be reused,which seriously limits its application.Polymer monodisperse microspheres have been widely used in liquid crystal display,drug controlled release,chromatographic analysis,enzyme immobilization and photonic crystal,etc.However,up to now,polymer microspheres have been rarely used for fluorescence detection.In this work,polyurea or polyurethane microspheres were prepared by the reaction of diisocyanate compounds with water or dialcohol by precipitation polymerization method.By introducing carboxyl group to improve the hydrophilicity of the microspheres,the crosslinking agent was added to prepare the crosslinking hydrophilic polyurethane microspheres.The effects of the amount of monomer,reaction temperature,solvent and catalyst type on the yield and particle size of microspheres were discussed,and the best experimental conditions were determined.The microspheres were characterized by IR,NMR and SEM.Fluorescence spectra show that the solid powders and water dispersions of polyurea and polyurethane microspheres can emit fluorescence.The effects of excitation wavelength and concentration of microsphere dispersion on the fluorescence properties were discussed.When polyurea or polyurethane microspheres were mixed with p-nitrophenol(4-NP),fluorescence quenching occurred in the system.The luminescence intensity of the system with different amounts of 4-NP was measured,and the linear relationship between the two was established.The detection limits of 4-NP were calculated and compared between polyurea and polyurethane microspheres.The influences of the types of microsphere polymers,p H and 4-NP analogs on the determination of 4-NP were discussed.By comparing the fluorescence emission spectra of microspheres with the ultraviolet absorption spectra of 4-NP under different conditions,the fluorescence quenching mechanism(internal filtration effect)of the system was clarified.The reusability of the fluorescent microspheres was characterized.It was found that the hydrophilic polyurethane retained 80% of the luminescence intensity after 6 reuses.