Synthesis and Application of Sequence-controlled Polymers

Sequence-controlled polymers are those with ordered units along their chains. The precision sequence of biological polymers, such as nucleic acid and peptides, plays a crucial role on physiological and sophisticated functions. Inspired by this, the synthesis of sequence-controlled polymers, that is, the placement of specific functional groups at desired positions on the polymer chain, has become one of the ultimate goals of polymer chemists, and received increasing attention in recent years. Up to date, there are a variety of methods to synthesize sequence-controlled polymers based on the step-growth and chain-growth polymerization mechanisms. Compared to the step-growth polymerization, the chain-growth polymerization is much more challenging to achieve sequence-controlled polymers because of the high activity and low propagating selectivity of the growing active center. Therefore, sequence-controlled polymerization is also considered as the "Holy Grail" in the field of polymer synthesis. Although a variety of methods have been developed to regulate polymer sequences, the pursuit of simple and efficient methods toward sequence-controlled polymerization has never stopped. This feature article summarizes the recent progresses on the synthesis of sequence-controlled polymers, and highlights our group's research in this area. Firstly, we built "supramolecular monomer" by exploiting the weak intermolecular hydrogen-bond interactions to create sequences with alternating feature. We also developed a "latent monomer" strategy based on the temperature-dependent furan/maleimide Diels-Alder reaction, and diverse sequence-controlled polymers were thus readily created. Moreover, a novel chemical route, based on orthogonal chain end deprotection and thiol-maleimide Michael addition, was developed in our group toward the monodisperse and sequence-defined polymers. Finally, the potential applications of the sequence-controlled polymers are also summarized and prospected.