In this study, we report on the synthesis of thermoresponsive polymers with different microstructures, a precisely tunable lower critical solution temperature (LCST) and terminal catechol anchors by copper(0) mediated living radical polymerization (Cu(0)-LRP). All the Cu(0)-LRP polymerizations were performed directly from the unprotected dopamine-functionalized initiators at ambient temperature or below in aqueous solution with full or close to full conversion obtained in minutes. The resulting polymers exhibited a designed molecular weight (MW), narrow MW distribution and high end-group fidelity capable of in situ block copolymerization. We demonstrate their application toward the surface modification of titanium dioxide nanoparticles by the successful preparation of smart nanocomposites with a self-flocculation effect. A "one-pot" strategy was then developed for the simultaneous polymerization and surface modification to simplify the multi-step purification and immobilization processes. The subsequent degradation of Rhodamine B under the irradiation of simulated solar light proved the potential application of hybrid nanocomposites in water treatment and a switching effect of photocatalytic ability below or above the LCST was also observed.