Preparation of polydisperse polystyrene‑block‑poly(4‑vinyl pyridine) synthesized by TEMPO‑mediated radical polymerization and the facile nanostructure formation by self‑assembly

This article reports a successful nanostructure formation from block copolymer having broad distribution of molecular weight. The block copolymer synthesis and the nanosphere formation are facile; therefore, it is promising for fabrication of nanostructure materials in large-scale manufactory. The polydisperse diblock copolymer of polystyrene-block-poly(4-vinyl pyridine) (PSVP) was prepared by the nitroxide-mediated radical polymerization that contains the fraction of poly(4-vinyl pyridine) block of 45 mol% and the overall polydispersity index of 2.08. The phase separation of PSVP was induced by the simple evaporation of co-solvent DMF:THF (70:30 v/v) of the PSVP solution. The SEM images of the self-assembled polydisperse PSVP display the spherical morphology with the diameter of ~ 50 nm, which is larger than that of block copolymer having narrow molecular weight distribution. By simply immersing the self-assembled film into iron chloride solution, the transformation from the spherical structure to the porous structure occurred directly without sacrificing the block copolymer component indicating the advantage of stimuli-response properties of the self-assembled PSVP. The results demonstrated that the polydisperse block copolymer could be used for the nanostructure formation by simple synthesis and evaporation procedures and, therefore, it is suitable for industrial applications.