Preparation And Application Of Polymer Microspheres In Photochromic Materials

Polymer microspheres, as a kind of new functional polymer materials with small size, large specific surface area, strong adsorption ability and a series of advantages, are used in a wide variety of scientific and technological fields with high value-added materials. The preparation of polymer microspheres is an important subject in the field of polymer synthesis.This paper is composed of three parts. In the first part, monodisperse porous polystyrene microspheres were prepared with the mixed solution of ethanol and water as dispersion medium and poly (vinylpyrrolidone) was used as dispersant. The even size of microspheres prepared at optimal process was about 1μm. Photochromic microspheres were obtained using polystyrene microspheres to absorb the spiropyrane. The effect of dispersion medium on the microspheres morphology was investigated. The adsorption parameters affecting microspheres adsorption quantity, such as the concentration of spiropyran solution and adsorption temperature, were studied in detail. Furthermore, photochromic properties of the microspheres were analyzed and PVA as coating was used to increase the fatigue resistance of photochromic microcapsules. The maximum adsorption quantity of particles was 6.58mg/g, when the concentration of spiropyran solution was 3.5mg/mL. The fatigue strength of microspheres loaded spiropyran was 25min. Howerve, high crosslinked degree of the microspheres cann’t be achived by dispersion polymerization. The second part of the experiment was carried out.Monodisperse cross-linked polystyrene microsphere have been synthesized by modified dispersion polymerization in which azodiisobutyronitrile(AIBN), poly(vinylpyrrolidone)(PVP) and divinylbenzene (DVB) were used as initiator, steric stabilizer and cross-linker, respectively. In this study, the delayed addition process in which the DVB added after the nucleation period was used. The average particle size, size distribution and surface morphology of particle were evaluated by laser particle size instrument and scanning electron microscopy. The surface morphology and size distribution of particles prepared with the cross-linker was added 1,2,3 and 4h after the start of the polymerization were investigated. Moreover, the effect of concentration of DVB on surface morphology and size distribution were discussed. The uniform micro-size polystyrene microspheres with the crosslink density were 10% were prepared when the cross-linker was added 4h after the start of the polymerization. Microspheres prepared by modified dispersion polymerization had a high degree of crosslinking. The specific surface area was small. Then, the third part of the experiment was carried out.In the third part, the porous microspheres were prepared by two-stage seed swelling method. In the experiment, the effect of swelling parameters on the porous particles was detailedly investigated, such as the swelling time of DBP and monomer, the molecular of seed particles, the amount of seed particles, the dosage of DVB and the amount of porogen. The morphology of particles was examined by SEM. The BET specific surface area and pore volume were taken with a surface area and pore size distribution analyzer. The specific surface area and pore volume of porous microspheres prepared at the optimum condition were 200.1566m2/g and 0.5719mL/g, respectively. Photochromic microspheres were obtained using polystyrene microspheres to absorb the spiropyrane and other photochromic materials. The maximum adsorption quantity of porous particles was up to 33.57mg/g. All microspheres loaded photochromic materials show good reversible photochromic properties. The fatigue strength of the different photochromic microspheres was up to 40min,420min and more than 800min, respectively, when photochromic microspheres were treated with xenon lamp whose irradiance was of 0.55w/m2 and wavelength was 420nm.