Poly[(styrene-b-isoprene) diblock macromonomer]s were prepared by free radical polymerization of corresponding vinylbenzyl-terminated diblock macromonomers (polyisoprene blocks = 21 similar to 26 wt%). Poly (diblock macromonomer)s consisting of side cains ((M) over bar(n) = 3600 g mol(-1)) exhibited degrees of polymerization in the range 54 similar to 200. The radius of gyration (R-g) and the cross-sectional radius of gyration (R-g,R-c) were determined by small-angle X-ray scattering. We studied the structural characterization of such pol(diblock macromonomer)s in a dilute solution.