Polymerization Order in the Synthesis of 2D Block Supramolecular Copolymers

In the synthesis of block polymers through living polymerization, the order in which the monomers are copolymerized can have a critical effect on the polymerization efficacy. The same should hold true for the synthesis of block supramolecular polymers; however, this remains unexplored. The effect of the order of the polymerization of the monomers in 2D seeded/living supramolecular block copolymerization of porphyrin-based monomers is investigated. Unlike 1D living polymers, 2D supramolecular polymers (or nanosheets) have two distinct propagation sites. It is shown that inverting the order of polymerization can lead to distinct growth modes; importantly, secondary nucleation is involved in one of these cases. If secondary nucleation takes place at the edges of the seeds prior to 2D growth, the resulting nanosheets tend to exhibit uncontrolled areas and edge roughness.