Structurally well-defined stereoregular diblock copolymers composed of syndiotactic polyallyltrimethylsilane (sPATMS) and poly­(methyl methacrylate) (PMMA) were prepared by using an α-bromoester-terminated sPATMS macroinitiator, which was chain extended by MMA using a cuprous halide-based atom transfer radical polymerization (ATRP) system. The α-bromoester-terminated sPATMS macroinitiator was prepared via the esterfication of hydroxyl-capped sPATMS with α-bromoisobutyryl bromide. The hydroxyl-capped sPATMS was generated via a selective chain transfer reaction to triethylaluminum (TEA) during the syndiospecific polymerization of allyltrimethylsilane (ATMS) conducted in the presence of syndiospecific ansa-metallocene catalysts. The proposed synthetic route not only offers the high-yield production of stereoregular sPATMS-b-PMMA but also provides the linking of the stereoregular block (sPATMS) with PMMA through a controlled/living radical polymerization process. Moreover, the proposed method offers effective control over the block chain length, the molecular weight distribution (M w/M n) and the stereoregularity of sPATMS block. Thus, the self-assembly of the resultant diblock copolymers produces well-ordered nanostructures from microphase separation, as evidenced by transmission electron microscopy and small-angle X-ray scattering results.