The synthesis of well-defined poly(methyl methacrylate)-b-poly(alkyl acrylate) diblock copolymers with a single fluorescent dye molecule (phenanthrene or anthracene) at the junction was investigated. The first block was prepared by the anionic polymerization (AP) of(meth)acrylate in THF at -78 degreesC, using the 3-(tert-butyldimethylsilyloxy)-1-propryl (aryl = 2-phenanthryl or 2-anthryl) monoadduct as the initiator. After the end group of the first block was transformed into alpha -bromoester, the diblock copolymer was formed by the atom transfer radical polymerization (ATRP) of the second methacrylate monomer using the first block as the initiator. The block copolymers were characterized by GPC, UV, and NMR. We found that the synthesis of anthracene-labeled diblock copolymer was perturbed by the reaction of the propagating poly(alkyl acrylate) radical with anthracene. Consequently, this synthesis has to start from the anionic polymerization of tert-butyl acrylate, followed by chain extension to poly(methyl methacrylate) by ATRP.