Engineering polymer interfaces has opened many applications to study small molecules, soft colloids, or enzymes due to their highly elaborated fabrication techniques, biocompatibility, and selectivity. Different types of surface modifications using specific polymers can transform the nature of the interfaces by constituting a single polymer or block-copolymer and find a number of applications in bio- and nanotechnology. In this dissertation, we aim to show the modification of various interfaces through ARGET-ATRP of stimuli-responsive polymer brushes. Furthermore, the developed switchable interfaces show unique applications in regulated interactions with soft colloids, rare cell isolation, spontaneous cell detachment, and enzyme carriers..