Carbon dioxide (CO2)‐responsive polymer nano‐objects are prepared by photoinitiated reversible addition‐fragmentation chain transfer dispersion polymerization of 2‐hydroxypropyl methacrylate and 2‐(dimethylamino)ethyl methacrylate (DMAEMA) in water at room temperature using a poly(poly(ethylene glycol) methyl ether methacrylate) macromolecular chain transfer agent. Kinetic studies confirm that full monomer conversions are achieved in all cases within 10 min of visible‐light irradiation (405 nm, 0.5 mW cm−2). The effect of DMAEMA on the polymerization is studied in detail, and pure higher order morphologies (worms and vesicles) are prepared by this particular formulation. Finally, CO2‐responsive property of the obtained vesicles is investigated by dynamic light scattering, visual appearance, and transmission electron microscope.