Transition metal-catalyzed directed C-H functionalization promises a straightforward route to polymerization but remains highly underexplored. We report herein the development of a polymer synthesis protocol based on Rh(III)-catalyzed N-nitroso-directed C-H olefination reaction. The single bifunctional monomer approach allows the high-yield generation of polymers with relatively narrow PDI under mild conditions. Further convenient denitrosation transformation furnishes responsive fluorescent polymers with metal ion-selective quenching behaviors. The high Hg2+ selectivity observed in one system provides a handy enabling tool for detecting this hazardous species.