Supramolecular Block Copolymers from Tricarboxamides. Biasing Co-assembly by the Incorporation of Pyridine Rings.

Abstract

The synthesis of a series of triangular-shape tricarboxamides endowed with three picolin or nicotin (compounds2and3) or just one nicotine unit (compound4) is reported and their self-assembling features investigated. The pyridine rings make compounds2-4electronically complementary with our previously reported OPETA1to form supramolecular copolymers.C3-symmetric tricarboxamide2forms highly stable intramolecular five-membered pseudocycles that impedes its supramolecular polymerization intopoly-2and the co-assembly with1to yield copolymerpoly-1-co-2. On the other hand,C3-symmetric tricarboxamide3readily formpoly-3with great stability but unable to form helical supramolecular polymers despite the presence of the peripheral chiral side chains. The copolymerpoly-1-co-3can only be obtained by a previous complete disassembly of the constitutive homopolymers in CHCl3. Helicalpoly-1-co-3arises in a process involving the transfer of the helicity from racemicpoly-1topoly-3, and the amplification of asymmetry from chiralpoly-3topoly-1. Importantly,C2v-symmetric4, endowed with only one nicotinamide moiety and three chiral side chains, self-assembles intoP-type helical supramolecular polymer (poly-4) in a thermodynamically controlled cooperative process. The combination ofpoly-1andpoly-4generates chiral supramolecular copolymerpoly-1-co-4, whose blocky microstructure has been investigated by applying the supramolecular copolymerization model.