Using molecular dynamics simulations, we study a simple and scalable method for fabricating patchy nanoparticles via the assembly of binary polymer blends under a rapid solvent exchange. Patchiness can be achieved by incorporating a glassy component, which kinetically traps the particle morphology along the path to the equilibrium configuration. Our simulations reveal that the number of surface patches increases for larger nanoparticles and for more asymmetric blend ratios, while the size distribution of the patches remains rather uniform. Other than multi-patch nanoparticles, Janus structures have been obtained for small nanoparticles. Further, ribbon structures with elongated surface domains have also been observed for more symmetric blend ratios. Our simulations demonstrate that the nanoprecipitation technique allows for independent control over nanoparticle size, patchiness and composition. This work gives microscopic insights on the static and dynamic properties of the self-assembled particles, and provides useful guidelines for fabricating tailored patchy nanoparticles for applications in various areas.