Supramolecular Block Copolymers from Tricarboxamides. Biasing Co‐assembly by the Incorporation of Pyridine Rings
Lucía López‐Gandul, Adrián Morón‐Blanco, Fátima García, Luis Sánchez
Abstract
Abstract The synthesis of a series of triangular‐shaped tricarboxamides endowed with three picoline or nicotine units (compounds 2 and 3 , respectively) or just one nicotine unit (compound 4 ) is reported, and their self‐assembling features investigated. The pyridine rings make compounds 2 – 4 electronically complementary with our previously reported oligo(phenylene ethynylene)tricarboxamides (OPE‐TA) 1 to form supramolecular copolymers. C 3 ‐symmetric tricarboxamide 2 forms highly stable intramolecular five‐membered pseudocycles that impede its supramolecular polymerization into poly‐2 and the co‐assembly with 1 to yield copolymer poly‐1‐co‐2 . On the other hand, C 3 ‐symmetric tricarboxamide 3 readily forms poly‐3 with great stability but unable to form helical supramolecular polymers despite the presence of the peripheral chiral side chains. The copolymer poly‐1‐co‐3 can only be obtained by a previous complete disassembly of the constitutive homopolymers in CHCl 3 . Helical poly‐1‐co‐3 arises in a process involving the transfer of the helicity from racemic poly‐1 to poly‐3 , and the amplification of asymmetry from chiral poly‐3 to poly‐1 . Importantly, C 2v ‐symmetric 4 , endowed with only one nicotinamide moiety and three chiral side chains, self‐assembles into a P ‐type helical supramolecular polymer ( poly‐4 ) in a thermodynamically controlled cooperative process. The combination of poly‐1 and poly‐4 generates chiral supramolecular copolymer poly‐1‐co‐4 , whose blocky microstructure has been investigated by applying the previously reported supramolecular copolymerization model.