Combining Orthogonal Chain-End Deprotections and Thiol-Maleimide Michael Coupling: Engineering Discrete Oligomers by an Iterative Growth Strategy

For the first time, we combined orthogonal maleimide and thiol deprotections together with thiol-maleimide coupling to synthesize discrete oligomers/macromolecules on gram scale with molecular weight up to 27.4 kDa (128mer, 7.9 g) via iterative exponential growth strategy with degree of polymerization (DP) at 2^n-1. By using the same chemistry, a "readable" sequence-defined oligomer and a discrete cyclic topology were also created. Furthermore, uniform dendrons were fabricated via either sequential growth (DP =〖 2〗^n-1) or double exponential dendrimer growth approach (DP =2^(2^n )-1) with significantly accelerated growth rate. This work offered a versatile, efficient and metal-free platform for construction of discrete oligomers with vast designability and high growth rate, which would greatly facilitate sophisticated structure-property research as well as applications of precise polymer-based materials.