The photochromic performance of polymer-dye conjugates was successfully tailored using the living radical polymerization technique ATRP. ATRP allowed the synthesis of photochromic dye-polymer conjugates consisting of polymer of defined chain length and polydispersity with a single photochromic dye attached at one end. Control over the photochromic switching speed was achieved solely thorough choice of the chain length of the polymer conjugate.