Impact of molecular shape on supramolecular copolymer synthesis in seeded living polymerization of perylene bisimides

Abstract

Supramolecular polymerization properties have been studied for a series of perylene bisimide (PBI) dyes containing identical hydrogen-bonding amide groups in imide positions but variable number or size of alkoxy substituents in bay-positions. Temperatureand time-dependent UV/vis and atomic force microscopy (AFM) studies revealed that the number and steric demand of the alkoxy substituents in baypositions has a strong impact on thermodynamically, and more importantly, on kinetically controlled supramolecular polymerization of these PBIs in solvent mixtures ofmethylcyclohexane and toluene. Our studies revealed that in the case of core tri- and tetramethoxy- substituted PBIs, the kinetically controlled aggregation pathway was suppressed completely, whereas monomethoxy and 1,7-dialkoxy PBI derivatives form kinetically trapped species. Besides, the monomethoxy-substituted PBI could be used successfully in self-seeded chain-growth polymerization of monomeric building blocks under precisely kinetically controlled conditions to obtain supramolecular polymers with controlled length and low polydispersity. Further, two-component seed-induced living copolymerization of the present PBI series revealed that the formation of supramolecular block copolymers is only feasible for appropriate combinations of PBIs and that the seeding efficiency is strongly dependent on the shape complementarity of the individual components applied. Thus, seeded supramolecular polymerization and copolymerization of PBIs could be modulated by subtle changes of the molecular shape through rational design of monomers.