We reveal unique hydrogen (H-) bonding patterns and exploit them to control the kinetics, pathways and length of supramolecular polymers (SPs). New bisamide-containing monomers were designed to elucidate the role of competing intra-vs. intermolecular Hbonding interactions on the kinetics of supramolecular polymerization (SP). Remarkably, two polymerizationinactive metastable states were discovered. Contrary to previous examples, the commonly assumed intramolecularly H-bonded monomer does not evolve into intermolecularly H-bonded SPs via ring opening, but rather forms a metastable dimer. In this dimer, all H-bonding sites are saturated, either intra-or intermolecularly, hampering elongation. The dimers exhibit an advantageous preorganization, which upon opening of the intramolecular portion of the H-bonding motif facilitates SP in a consecutive process. The retardation of spontaneous self-assembly as a result of two metastable states enables length control in SP by seed-mediated growth.

A complex aggregation pathway towards two diastereomeric P and M supramolecular helices arises from the aggregation of a short, chiral, and rigid oligo(phenyleneethynylene) [OPE, (S)-1]. Thus, while Agg I aggregate is obtained when a DCM solution of (S)-1 is diluted with MCH at room temperature, Agg II aggregate is generated only after a slow heating (353 K)/cooling (273 K) process. Interestingly, during Agg I formation (mechanism 1), short P chain oligomers are produced, which have a great tendency to aggregate in plane, yielding brick-like nanostructures that halt the aggregation process. On the other hand, after a heating/cooling cycle, long M type columnar helical aggregates (Agg II ) are obtained, formed by individual supramolecular polymer chains (mechanism 2) easily visualized by AFM. The two different P/M orientations obtained for Agg I and Agg II reveal the dynamic character of the system and its ability to create diastereomeric helical structures under the right conditions. Different experimental protocols were explored to prepare long M type columnar helical aggregates, which are not obtained by using the previous MCH/DCM 99/1 (v/v) solvent mixture. The generation of the desired M oriented supramolecular polymer is achieved when toluene is added to the solvent mixture in a 97/ 2/1 MCH/Tol/DCM (v/v/v) ratio.

The macromolecular helicity of poly(phenyl isocyanate)s can be tuned by a conformational switch of the chiral initiator through a domino effect.