We propose a new method to large-scale synthesize polymeric colloidal dimers by electrostatically-mediated intramolecular cross-linking of an example di-block copolymer of poly(isoprene)-b-poly(vinylpyridine) (PI-b-P4VP) in highly concentrated solutions. The synthesis is orthogonally performed in a highly polar solvent such as DMSO. The first colloid is achieved by intramolecular cross-linking of the PI block with 1,6-hexanediisothiocyanate after modification with 2-mercaptoethylamine hydrochloride to introduce an electrostatic interaction. The Janus single-chain nanoparticle of cPI-P4VP is derived. In the sequential step, the other colloid is achieved by intramolecular cross-linking the P4VP block of cPI-P4VP with 1,5-diiodopentane after modification with iodoethane. The polymer colloidal dimer of cPI-cP4VP is thus achieved. The Janus cPI-cP4VP dimer is composed of two different domains: the cPI containing residual amine and cyanate groups and the cP4VP containing residual pyridine and quaternized groups. The dimer can be synthesized at a higher concentration of 100 mg/mL. A huge family of functional colloidal dimers is expected after selectively loading materials within the desired colloidal domains.