Abstract

We have developed the first rational strategy for ‘chain-growth’ supramolecular polymerization composed of defined initiation and propagation steps, featuring ‘metastable’ bowl-shaped monomers that are designed to polymerize at ambient temperatures only when mixed with tailored initiators, and succeeded in forming noncovalent polymers with a uniform and desired chain length in a precise stereoselective manner. Over the last decade, significant progress in supramolecular polymerization, initiated by Lehn and Meijer and their coworkers has had a substantial impact on the design of functional soft materials.1,2 However, despite recent advances for obtaining polymers with narrow PDI , most studies are still based on a preconceived notion that supramolecular polymerization follows the step-growth mechanism, which precludes control over chain-length, sequence, and stereochemical structure. Here we report the realization of chain-growth polymerization by designing metastable monomers with a shape-promoted intramolecular hydrogen-bonding network.3 The monomers are conformationally restricted from spontaneous polymerization at ambient temperatures, but begin to polymerize with characteristics typical of a living mechanism upon mixing with tailored initiators. The chain growth occurs stereoselectively and therefore enables optical resolution of a racemic monomer.

References (1) J. -M. Lehn, Macromol. Chem. Macromol. Symp. 1993, 69, 1. (2) E. W. Meijer et al., Science 1997, 278, 1601. (3) Kang and Miyajima et al., Science 2015, 347, 646.