Synthesis of monodisperse zinc sulfide particles graftedwith concentrated polystyrene brush by surface-initiatednitroxide-mediated polymerization

摘要

Monodisperse zinc sulfide (ZnS) particles of diameters ranging from 120 to 400 nm wereprepared and then coated with a thin layer of silica (SiO_2). After the surface modificationwith an alkoxyamine derivative, polystyrene (PS) brushes of chain lengths ranging from30,000 to 114,000 in M_n with relatively low polydispersities less than 1.5 in M_w/M_n weresuccessfully grafted by surface-initiated nitroxide-mediated polymerization, where theM_n and M_w are the number- and weight-averaged molecular weights, respectively. Thegraft density reached a value as high as 0.9 chains nm~(-2). These core-shell hybrid particles(ZnS@SiO_2-PS) were highly dispersible, without any aggregation, in various solvents goodfor PS, also forming a monolayer at the air-water interface by spreading its solution. Thetransmission electron microscopic observation of the monolayers deposited on a solid sup-port revealed two-dimensionally close-packed arrays of particles. These monolayers exhib-ited a beautiful structural color dependent on the angle of incident light because of such anordered array of the ZnS cores with a high refractive index. Hollow spheres constituted of aSiO_2shell with well-defined, high-density PS brushes were first synthesized by selectivedissolution of the ZnS core from the ZnS@SiO_2-PS hybrid particle.