Effect Of Coordination On Reactive Micellization Of Primary Amine Based Block Copolymers

Dynamic Combinational Chemistry （DCC） is a new chemistry division that wasdeveloped by the inspiration of reversible reactions in living organisms, which leadsto the most thermodynamics stable products with the features of reversible reactionsand molecular recognition. Reactive self-assembly of polymers based on DCC hasattracted growing attentions in recent years. This thesis explored the metal ioncoordination effect on reactive micellization of primary amine based blockcopolymers. To this end, well-defined poly[N-（2-hydroxy-propyl）-2-methyl-acrylamide]-b-poly（N-hexylmethacrylamide）（PHPMA-b-PAHMA） copolymers weresynthesized.2-Hydroxy-5-methoxybenzaldehyde （HMBA） and Ni^II（HMBA）₂wereutilized as guests in DCC of PHPMA-b-PAHMA. The formation of imine andmechanism of coordination-induced reactive micellization were intensively studiedusing UV-vis spectroscopy, dynamic light scattering and¹H NMR studies. The resultsdemonstrated that both HMBA and Ni^II（HMBA）₂rapidly reacted with the primaryamine groups of PAHMA units, leading to the collapse of PAHMA chains, andforming hydrophobic domains. Adding small amount of Ni^II（HMBA）₂remarkablyshorten the critical time needed for starting phase transition, effectively prevented theformation of large aggregates, and gave rise to the rapid micellization. Moreover, Theeffect of coordination-directed collapse was amplified on adding relatively largeamount of Ni^II（HMBA）₂. The collapse of polymer chains predominantly caused by thehydrophobic interactions at [Ni^II]₀:[HMBA]₀<0.1. The increase of complex fractiongave rise to the inter-chain coordination, leading to the more compact micelles at0.1<[Ni^II]₀:[HMBA]₀<0.225. Further increasing the complex led to the relatively largeraggregates.¹H NMR studies evidenced that the metal coordination effectivelyenhanced desolvation, thus directed micellization process. This coordination-directedmicelles exhibited typical dynamic exchange features. Accordingly, Ni^II（HMBA）₂acted as an efficient amplifier for the hierachical architectures of supra-molecules.Thus, this thesis extended and enriched the concept of polymeric DCC.