Poly(styrene-block-4-vinylpyridine) (PS4VP)CdS nanocomposites containing different concentrations of CdS were synthesized by an in situ method. Scanning electron microscopy and transmission electron microscopy results indicate that the morphologies of PS4VPCd(II) and PS4VPCdS were controlled by the Cd(II) concentration and the solvent, respectively. The effects of the CdS concentration on the crystal style of CdS in PS4VPCdS and the photoluminescence (PL) properties of the PS4VPCdS were also examined. By a comparison of the PL spectra of PS4VPCdS in solutions, films, and powders, the PL mechanism of PS4VPCdS was also delivered. The PS4VPCdS nanocomposite shows potential for application in water-soluble fluorescence probes. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013