Playing construction with the monomer toy box for the synthesis of multi-stimuli responsive copolymers by reversible deactivation radical polymerization protocols

In this review article, we survey the 2016-June 2021 scientific literature on the synthesis of multi-stimuli responsive (MSR) polymers, the main focus being on reversible deactivation radical polymerization techniques (RDRPs, also known as controlled radical polymerizations). In fact, along more than 40 years of extensive research, RDRPs have boosted the synthesis of stimuli-responsive polymers. RDRPs are now robust, versatile, relatively user-friendly and even interconvertible, thus allowing control over composition, sequence, and topology of polymers. Such control can afford materials with well-defined responses to physical, chemical, and biological external stimuli. Furthermore, "click" reactions are used to combine macromolecular precursors or to introduce specific functional groups in the target structure. As a result, MSR polymers are obtained from diverse combinations of commercial or specially synthesized building blocks arranged at will into desired sequences and architectures. Thanks to this versatility, self-assembling polymeric structures are designed either to respond to triggers and perform specific applicative tasks, or to investigate the influence of structural variables on the responsivity of polymers. The "green" trend emerging in the field of responsive polymers and RDRPs is also briefly discussed.