Poly(styrene-co-2-vinylnaphthalene) with a 1.25% fraction of naphthyl fluorophores is studied in two polymeric hosts, polystyrene and poly(vinyl methyl ether). In the polystyrene host, measurement of the electronic excitation transport-induced fluorescence polarization anisotropy decay, r(t), in conjunction with a previous quantitative statistical theory of electronic excitation transport on lightly tagged polymer chains, allows a determination of the copolymer radius of gyration. Comparison with light scattering measurements from the literature establishes the theta-condition nature of this solid system. Poly(vinyl methyl ether) forms a compatible polymer blend with polystyrene. Analysis of r(t) data shows that the radius of gyration of a copolymer molecule is expanded in poly(vinyl methyl ether) relative to the theta-condition at room temperature. The synthesis of poly(styrene-co-2-vinylnaphthalene) is detailed.