Studies On The Preparation And Hierarchical Self-assembly Of Polymeric Nanoparticles

Recently, due to the special properties (such as temperature, light and electric sensitive) and the potential application in the fields of medical and electrical engineering, polymeric nanoparticles have received widely attentions.This thesis contains two sections:Section one:the preparation of fluorescent core-shell aggregates via inter-chain cross-linking. The aggregates were prepared by simply cross-linking the poly(4-vinylpyridine) (P4VP) block of polystyrene (PS)-block-P4VP block copolymer in common solvent DMF using propargyl bromide (PB) as cross-linker. PB quarterized pyridine units of the P4VP block chains firstly, leading to the grafting of PB to the P4VP block chains. Then, the acetylene groups in the PB grafts polymerized with each other and thus cross-linked the P4VP block chains. The cross-linking reaction forced aggregation of the P4VP block chains. However, with the cross-linking reaction proceeding, the PS block chains gathered around the P4VP cross-linked network, and finally localized the cross-linking reaction. As the results, core-shell aggregates with the cross-linked P4VP/PB network as the core and PS as the shell were formed. We further confirmed that the conjugated carbon-carbon double bonds in the structure of polyacetylene (the product of the polymerization of the PB grafts) in the core were fluorescent. Besides, the core was with a loosely aggregated structure and, to a certain extent, swollen, which made the penetration of chemical species into the core conveniently. Therefore, the chromophores responded promptly to various metallic ions and basic species. It was also due to the loosely aggregated structure, the primary core-shell aggregates can further self-assemble into regular superparticles in water the selective solvent for the pyridinium groups, which were the product of the mentioned quarterization reaction and located in the core of the primary core-shell aggregates.Section two:preparation of tadpole-like single chain nanoparticles via intra-chain cross-link. We have confirmed that intra chain cross-linking reaction between PS-b-P4VP and PB in DMF can be realized via controlling the concentration of the block copolymer. The intra-chain cross-linking reaction led to tadpole-like single chain nanoparticles where the P4VP block collapsed into, a single chain sphere due to the cross-linking reaction, as revealed by TEM observations and GPC-MALS characterization. It is believed that the presence of PS block help to prevent from the inter-chain crosslinking reaction.