The Morphology, Structure Control And Mechanism Of Aggregates By Self-Assembly

Macromolecular self-assembly produces nanostructures with complex morphology and ordered structure, driven by non-covalent interactions such as van der Waals interaction, hydrogen bonding, electrostatic interaction, hydrophobic interaction, host-guest inclusions, and dipole-dipole interaction. Macromolecular self-assembly has become an important pathway to fabrication of nanomaterials which are promising in the fields ranging from electronics, photonics, functional devices and drug delivery. This thesis focuses on macromolecular self-assembly and its application, including three sections as follows.(I) The mechanism of spheric micelles to worm-like micelles and their applicationThe worm-like micelles are attracting increasing attention owing to their many important applications in the fields of drug delivery and nano-device fabrication. Till now, the worm-like micelles are fabricated through the self-assembly process of the block copolymer, but the formation mechanism of worm-like micelles is still unclear. In this study, we synthesized two kinds of amphiphilic diblock copolymer poly(ethyleneoxide)-b-poly(4-vinyl pyridine)(PEO-b-P4VP) and poly(N,N-dimethyl acrymide)-b-poly(4-vinyl pyridine)(PDMA-b-P4VP) by controlled radical polymerizations. The spheric micelles with P4VP as the core and PEO or PDMA as the shell were prepared by self assembly of PEO-b-P4VP or PDMA-b-P4VP in H2O/CH3OH (4:1, V/V) mixed solvents. Under certain experimental conditions, the common solvent methanol was removed gradually, and thus the interfacial energy between the core surface and the medium increases. This results in the transformation of the spherical micelles to worm-like micelles. Furthermore, we realized the "random copolymerization" and "block copolymerization" of the two kinds of the spherical micelles, which revealed that the spherical micelles to worm-like micelles transformation results from the core-core coupling of the spherical micelles. Based on this mechanism, we prepared a variety of worm-like micelles with novel structures.(II) Self-assemblies for fabricating monodisperse polymeric superparticles with a bicontinuous nanostructureTriblock copolymer polystyrene-b-polyacrylic acid-b-poly(sodium 4-styrenesulfonate (PS-b-PAA-b-PSSNa) self-assembled into core-shell-corona micelles in DMF, the selective solvent for PS and PAA. The self-limited aggregation of the micelles at the early period of the water addition led to the narrowly size-distributed superparticles, which are large enough for formation of nanostructures within them. With further water addition, PS chains contract and PSSNa chains are swollen, driving self-assembly of the copolymer with the superparticles. When the PAA block chains in the primary micelles are slightly crosslinked by Cu2+, during the phase transition, the formation of cylinders within such the crowded and confined space results in the bicontinuously structured superparticles (BSPNPs) formed by interconnected nanocylinders. The whole process experiences consecutive molecule-particle-molecule self-assembly process.(III) Phosphorescent coordination polymeric micelles that can enter and then be triggered by histidine to release the anti-cancer residual within cancer cellsIn this study, functional polymeric micelles with folic acid (FA) end-capped poly (ethylene glycol) (PEG) as the shell and phosphorescent Ir(pq)2/poly(4 vinylpyridine) (P4VP) (pq represents 2-phenylquinoline) complex as the core were prepared simply through complexation between FA-PEG-b-P4VP and [Ir(pq)2]2Cl2. The micelles are capable of entering cancer cells. It is significant that, after the cellular internalization of the micelles, histidine located within the cells triggered the release of Ir(pq)2 residual from the micelles, and then the residual, an potential anticancer drug, entered the nucleus. Since both the micelles and the Ir(pq)2 residual are phosphorescent, the processes of cellular internalization and nuclear entrance of Ir(pq)2 residual can be clearly tracked.