The Competitive Aggregation Pathway of an Asymmetric Chiral Oligo(p‐phenyleneethynylene) Towards the Formation of Individual P and M Supramolecular Helical Polymers

다국어 초록 (Multilingual Abstract)

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 AggI aggregate is obtained when a DCM solution of (S)‐1 is diluted with MCH at room temperature, AggII aggregate is generated only after a slow heating (353 K)/cooling (273 K) process. Interestingly, during AggI 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 (AggII) are obtained, formed by individual supramolecular polymer chains (mechanism 2) easily visualized by AFM. The two different P/M orientations obtained for AggI and AggII 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.
Aggregation of a short, chiral, and asymmetric oligo(phenyleneethynylene) [OPE, (S)‐1] goes through a competitive pathway in which the two diastereomeric P and M supramolecular helices can be selectively produced by choosing the correct experimental conditions. Thus, while an M supramolecular aggregate is obtained in MCH/DCM [AggII], the diastereomeric P aggregate [AggI] is produced by adding toluene to the solvent mixture MCH/Tol/DCM.