Synthesis of Non-natural Polymers with Controlled Primary Structures
This chapter summarizes advances made in the field of sequence-controlled polymers over the last years. Inspired by natural polymers such as DNA and proteins, sequence-controlled polymers are synthetic macromolecules with controlled primary structures. Although this new type of polymers is relevant for numerous applications, the present chapter focuses mainly on their synthesis. Recently reported strategies for preparing sequence-controlled polymers in chain-growth, step-growth, and multistep-growth polymerizations are described and critically analyzed. In a first section, monomer sequence regulation in chain-growth processes such as anionic, cationic, and controlled radical polymerization is discussed. Recent concepts for controlling monomer sequences in ring opening polymerizations are also presented in this section. Afterwards, the synthesis of precision periodic microstructures by step-growth polymerization is discussed in a dedicated section. In particular, emphasis is put on recent methods such as acyclic diene metathesis polymerization and copper-catalyzed azide–alkyne cycloaddition step-growth polymerizations. Recent approaches employing multicomponent reactions are also discussed in this second section of the chapter. In the third and last section, approaches allowing the synthesis of monodisperse macromolecules with perfectly defined monomer sequences are described. In particular, solid-phase iterative methodologies are discussed in detail. Some information on recent concepts involving templates and molecular machines is also provided. Overall, this chapter gives a comprehensive view on the development of the field during the last five years.