Core-crosslinked nanocylinders with well-defined shape and narrowly-dispersed size are prepared by using S2Cl2 to react with the alkenyl functionalities of the PNb-g-PIp-based core domain of cylindrical core-shell brush block copolymer, PNb-g-PIp-b-PtBA (see figure). This strategy potentially may be further extended by using brush copolymer templates having different compositional, structural and topological features for the synthesis of a broad variety of crosslinked nanostructures with diverse shapes and sizes.