Construction Of Interfacial NH₂-enriched Reactive Nanomaterials Via Polymerisation-induced Self-assembly

Self-assembly of amphiphilic block copolymer into nano-objects suffers from undesired encapsulation of hydrophobic active motifs of core-forming block, which deteriorates the performance as aqueous catalysts. This problem can be circumvented by polymerizetion-induced self-assembly(PISA). Principle of PISA conducted in aqueous media is that a water-soluble stabilizer block is chain-extended using a water-miscible monomer via RAFT polymerization. Initially, a soluble diblock copolymer is obtained, but at some critical degree of polymerization the growing GPCond block becomes water-insoluble, which causes in situ self-assembly. On the basis of systematic studying documents, the paper reports a new approach of one-pot production of reactive nano- particles whose active motifs decorate on the core-shell interfaces in aqueous solution at room temperature. The aqueous dispersion PISA procedure was fast and efficient.Firstly, we demonstrate a fast RAFT aqueous dispersion polymerisation of a diacetone acrylamide(DAAM) monomer, using a poly(2-hydroxypropyl methacrylamide)(PHPMA) macromolecular chain transfer agent(macro-CTA) and a sodium phenyl-2,4,6-trimethylbenzoylphosphinate(SPTP) photoinitiator under visible light irradiation at 25 oC. PISA is induced by polymerisation through sequentially dehydration, phase separation, micellization and reaction acceleration, leading to full conversions within 30 min and finally assembled into biomodal sphere nanoparticles. The above results show that the aqueous dispersion PISA procedure was fast and efficient using PHPMA as macro-CTA under visible light. Then on this basis, this paper demonstrates a new approach to reactive block copolymers with perfect accessibility and reactivity. Replacement of minimal DAAM by NH3+-based monomer(AEAM) induces the slight hydration of core-forming acceleration of both AEAM and DAAM indicates the effective enrichment of both of them due to the slight hydration inside PISA-cores. Moreover, the simultaneous process of in situ self-assembly and chain growth facilitates adjustment of newly-added NH3+-units outwardly toward core-shell interfaces while the vast majority of DAAM units collapse into hydrophobic PISA-cores. This leads to a timely and selective self-assembly into new reactive nanoparticles, whose NH3+-motifs decorate over core-shell interfaces. The above results show that the copolymerisation of a small amount of AEAM and vast DAAM leads to the formation of interface-decorated NH3+ functional motifts block copolymer nanoparticles.The paper demonstrates the accessibility of the interface NH3+ motifts using aqueous electrophoresis and 1H NMR spectroscopy. The reactivity of PISA nanoparticles were testified by virtue of simultaneous imine conversion and Zn(II)-coordination of interfacial NH3+-motifs. These nanoparticles are well suitable for production of advanced nano-reactors, whose functionalized dative metal centres decorate on core-shell interfaces. The above results show that the resultant interface-decorated reactive block copolymer nanoparticles have perfect accessibility and reactivity. The above strategy circumvented the encapsulation of hydrophobic active motifs of core-forming block.In conclusion, this paper demonstrated a fast PISA via aqueous dispersion RAFT polymerisation of a commercially available specialty monomer DAAM using a water-soluble PHPMA macro-CTA under visible light irradiation at 25 °C. Copolymerization of DAAM and AEAM led to the timely and selective self-assembly of the core-forming block into new reactive nanomaterials whose interfacial NH3+-motifs are accessible to the substrates in water. Thus, these reactive nanoparticles are promising as precursors of metalloenzyme-inspired aqueous catalysts.