Herein, an ω,ω-heterodifunctional macromolecular reversible addition-fragmentation chain transfer (macro-RAFT) agent containing two different RAFT end groups was synthesized and employed to mediate aqueous photoinitiated RAFT dispersion polymerization of a methacrylic monomer. Because of the different RAFT controllability of two RAFT end groups toward methacrylic monomers, the RAFT end group with good controllability dominated the polymerization while the other RAFT end group with poor controllability was unreacted, leading to the formation of linear block copolymers. Because of the unique structure of the linear block copolymers, a diverse set of block copolymer nanoparticles with rich RAFT groups at the interface of the hydrophilic corona/the hydrophobic core were successfully prepared. Finally, μ-A(BC)C miktoarm star block copolymer nanoparticles were prepared by RAFT seeded emulsion polymerization of an acrylic monomer, which enables the further morphological control over polymer nanoparticles. We believe that the utilization of an ω,ω-heterodifunctional macro-RAFT agent in heterogeneous RAFT polymerization will offer considerable opportunities for the rational synthesis of well-defined molecular architectures and polymer nanoparticles.