Polyisoprene (PI) star polymers with many arms formed a body-centred cubic (BCC) structure near the overlap threshold (C*) in solution. After the PI stars (arm number n above about 90) revealed a superlattice of BCC structure in vinyl monomers (methyl methacrylate, styrene and t-butyl acrylate), the hybrid structures were constructed by locking the ordered superlattice into a solid matrix by means of free radical polymerization of the vinyl monomers. The morphologies of the polymerization-induced phase separation depended strongly on the arm number, propagation rate of the vinyl monomers, and the addition of chain transfer or cross-linking agents.