Programmable selectivity of metal–imine bond coordination in subcomponent self-assembly of a primary amine based block copolymer

Abstract

We describe the programmable selectivity of intra-/inter-chain coordination in the subcomponent self-assembly of a primary amine based block copolymer. A well-defined poly(6-aminohexylmethacrylamide hydrochloride)-block-poly(N-2-hydroxypropylmethacrylamide) (PHPMA-b-PAHMA) was synthesized via visible light activated aqueous RAFT polymerisation at 25 °C. The conjugation of 2-hydroxy-5-methoxybenzaldehyde (HMBA) in the absence or presence of small fractions of the nickel ion complex was monitored using ¹H NMR and UV spectroscopy. Subcomponent self-assembly and the programmable selectivity of intra-/inter-chain coordination were studied using dynamic light scattering and ¹H NMR. The results demonstrated that the coordinated HMBA was much more reactive than the free HMBA, which promoted the collapse and hydrophobic association of polymer chains and thus brought about the autocatalysis of imine formation inside the collapsed “hot spots”. The polymer chains progressively assembled into narrowly-distributed nanoparticles on adding small fractions of Ni^II(HMBA)₂ rather than autopoietically splitting into smaller ones, as observed on adding pure HMBA. More importantly, the diversity of subcomponent self-assembly and solubility of aggregates originated from the programmable selectivity of intra-/inter-chain coordination.