A new p-phenylene-vinylene-thiophene-based siloxane block copolymer has been synthesized. The copolymer consists of alternating rigid and flexible blocks. The rigid blacks are composed of phenylene-vinylene-thiophene-based units, and the flexible blocks are derived from 1,3-dialkyldisiloxane units. The former component acts as the chromophore, and allows fine tuning of band gap for blue-light emission, while the latter imparts good solubility of the copolymer in organic solvents, and thus, should enhance processibility of the resulting copolymer. The thermal properties of the copolymer have been characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The photoluminescence (PL) of the copolymer in solution and in cast film has been studied. The effects of concentration on the PL intensity of the new copolymer in polymer blends with poly(methyl methacrylate) (PMMA) and polyvinyl carbazole) (PVK) have also been described. Efficient energy transfer from PVK to the new block copolymer in the blended film was observed.