A series of polystyrenes having low molecular weight (4600-23,100) and narrow molecular weight distribution and functionalized with a benzophenone group at one or both ends of the chain have been prepared through anionic polymerization. Then the terminal benzophenone groups have been transformed into 1,2-bis(trimethylsilyloxy)tetraphenylethane (or benzopinacolate) groups by the duplication reaction with free benzophenone in the presence of chlorotrimethylsilane and hexamethylphosphorous triamide (HMPT) or hexamethylphosphoramide (HMPA), producing model thermal macroinitiators of free radical polymerization with well-defined structure. Polymerization of MMA initiated by these macroinitiators was carried out yielding poly(styrene-b-methyl-methacrylate) (PS-b-PMMA).