The poly(C-60-co-styrene)s prepared by radical copolymerizations of C-60 and styrene in bulk were characterized by multiple-detector size-exclusion chromatographs consisting of a refractometer, a differential viscometer, and/or a right-angle laser-light scattering photometer. The multidetector systems enabled the determinations of reliable, absolute molecular weights of the copolymers. The plots of intrinsic viscosity vs. molecular weight and radius of gyration vs. molecular weight offered valuable information about the molecular architectures of the copolymers. The slopes of the plots reveal that the structure of the copolymer changes with its C-60 content: the copolymer with a low C-60 content of 0.58 wt% possesses a linear structure, whereas its conger with a high C-60 content of 1.14 wt% possesses a branched structure. (C) 2004 Elsevier Ltd. All rights reserved.