This review describes different synthetic strategies towards sequence-defined, monodisperse macromolecules, which are built up by iterative approaches and lead to linear non-natural polymer structures. The review is divided in three parts: solution phase-, solid phase-, and fluorous- and polymer-tethered approaches. Moreover, synthesis procedures leading to conjugated and non-conjugated macromolecules are considered and discussed in the respective sections. A major focus in the evaluation is the applicability of the different approaches in polymer chemistry. In this context, simple procedures for monomer and oligomer synthesis, overall yields, scalability, purity of the oligomers, and the achievable level of control (side-chains, backbone, stereochemistry) are important benchmarks.

A novel strategy for the incorporation of carbon dioxide into polymers is introduced. For this purpose, the Ugi five-component condensation (Ugi-5CC) of an alcohol, CO2 , an amine, an aldehyde, and an isocyanide is used to obtain step-growth monomers. Polymerization via thiol-ene reaction or polycondensation with diphenyl carbonate gives diversely substituted polyurethanes or alternating polyurethane-polycarbonates, respectively. Furthermore, the application of 1,12-diaminododecane and 1,6-diisocyanohexane as bifunctional components in the Ugi-5CC directly results in the corresponding polyamide bearing methyl carbamate side chains (M¯n = 19 850 g mol(-1) ). The latter polymer is further converted into the corresponding polyhydantoin in a highly straightforward fashion.

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The concept of sequence-definition in the sense of polymer chemistry is introduced to conjugated, rod-like oligo(phenylene ethynylene)s via an iterative synthesis procedure. Specifically, monodisperse sequence-defined trimers and pentamers were prepared via iterative Sonogashira cross-coupling and deprotection. The reaction procedure was extended to tetra- and pentamers for the first time yielding a monodisperse pentamer with 18% and a sequence-defined pentamer with 3.2% overall yield. Furthermore, three novel trimers with a 9H-fluorene building block at predefined positions within the phenylene ethynylene chain were synthesised in 23–52% overall yields. Hence, it was confirmed that a functionality of interest can be incorporated selectively at a pre-defined position of these monodisperse oligomers. All respective intermediate structures were fully characterised by proton and carbon NMR, mass spectrometry, size-exclusion chromatography, and IR spectroscopy. Additionally, thermal and optical transitions are reported for the different oligomers.

Back Cover: Synthesis strategies towards monodisperse, sequencedefined macromolecules are presented in this review, including conjugated and non‐conjugated linear oligomers. Hence, sequencedefined macromolecules containing defined monomer sequences as well as monodisperse oligomers with a regulated monomer sequence are considered. Further details can be found in article number https://doi.org/10.1002/marc.201600711 by Susanne C. Solleder, Rebekka V. Schneider, Katharina S. Wetzel, Andreas C. Boukis, and Michael A. R. Meier*.