Microfluidically mediated atom-transfer radical polymerization

Surfaces with a controlled gradient of polymer brushes were fabricated via microfluidically mediated atom-transfer radical polymerization (ATRP). This methodology used a sealed sandwiched setup with a parallel alignment of the initiator-substrate with the metal substrate. A syringe-pump injected small volumes of Cu(I)/L activator/monomer solution directly into the bottom of the setup while ATRP at the frontal initiator-substrate was simultaneously initiated. The trace amount of injection solution locally confined polymerization to occur only on areas in contact with the solution which resulted in the spontaneous formation of gradient structures. A surface-attached polymer gradient was regulated via either the solution injection rate or monomer/catalysis concentration, thereby yielding a controllable gradient with uniformly grafted polymers.