Publication
Biopolymers often show deterministic chain folding templated by repeat unit sequences whose conformations are locked in by intramolecular interactions. In this work, we have used repeat units based on rigid anthracene or acridine scaffolds, which we refer to as "U-turn" repeat units, to template chain folding reminiscent of beta-serpentine folds in bulk synthetic polyamides. Unlike the rigid kinked repeat units present in certain commercial semiaromatic polyamides, the acridine-based U-turn repeat units did not impede crystallization in the polyamides, whose crystalline phase was shown to be stabilized by infinite arrays of intermolecular hydrogen bonds and pi-pi interactions between the acridine units. This led to a unique layered crystalline structure characterized by a well-defined lamellar thickness that depended on the length of the aliphatic spacers between the U-turn repeat units and regular adjacent re-entrant chain folding, which is not usually expected for semiaromatic polyamides crystallized at high supercooling. Our work hence provides the first example of the introduction of deterministic chain folding into a nonpeptidic polyamide in order to tailor its crystalline morphology and may consequently open up new perspectives for the molecular design of structural materials.