Nanosized Micelles Formed by the Self-assembly of Amphiphilic Block Copolymers with Luminescent Rhenium Complexes

Abstract

We have synthesized a series of polystyrene-block-poly(4-vinylpyridine)s (PS-b-PVP) to which luminescent tricarbonyl(2,2‘-bipyridyl)rhenium(I) complexes were attached. The rhenium complexes could induce the self-assembly of the copolymers into nanosized micelles with different shapes and dimensions, depending on the block size distribution of the copolymers and the solvent system being used. In general, spherical micelles were observed when methanol, a nonsolvent for the polystyrene block, was added to a copolymer solution in dichloromethane. Micellization was observed when the added methanol concentration was approximately 30%. When toluene, a nonsolvent for the poly(4-vinylpyridine) block, was added to the copolymer solution in dichloromethane, micelles with different interesting shapes were observed. For copolymers with larger PVP block size, spherical micelles were observed. When the relative block size of the PVP block was reduced, the micelles gradually changed to disk or vesicle structures and then to rodlike structures. The rhenium complex can act as a luminescent probe in the resulting nanosized micelles and provide sufficient contrast for electron microscopic studies. Significant changes in luminescence spectra were observed after the micellization.

pH‐Switchable Complexation between Double Hydrophilic Heteroarm Star Copolymers and a Cationic Block Polyelectrolyte

“…[34] Taking this perspective, the selective alteration of the solubility of one block, realized via polyelectrolyte complexation, [35][36][37][38][39][40][41] hydrogen-bonded complexation, [42][43][44][45] stereocomplexation, [46] and metal-ion complexation [47][48][49][50] have been successfully employed to fabricate colloidal nanoparticles, possessing micelle-like core-shell structures.…”

“…pH-Switchable Complexation between (PEO) n -PDVB-(PMAA) n and PEO 113 -b-PQDMA 48 We further studied the stabilization effect of a neutral-cationic diblock copolymer, PEO 113 -b-PQDMA 48 , on the unimolecular micelles with hybrid coronas, (PEO) n -PDVB-(PMAA) n , at different pH conditions. Two types of non-covalent interactions need to be considered here: hydrogen-bonding interactions between the PEO and PMAA at low pH, and electrostatic interactions between the PQDMA and ionized PMAA at high pH.…”

“…Thus, (PEO) n -PDVB-(PMAA) n can be viewed as unimolecular micelles with hybrid PEO and ionized PMAA arms. Upon mixing with PEO 113 -b-PQDMA 48 , the mixed solution with the weight fraction of PEO 113 -b-PQDMA 48 being 0.6 was stable and exhibited a bluish tinge, characteristic of colloidal particles. Dynamic LLS revealed an average hydrodynamic radius, hR h i, of %52 nm.…”

“…At low pH, (PEO) n -PDVB-(PMAA) n exhibited macroscopic phase separation, which can be ascribed to the hydrogen-bonding interactions between the PEO and the PMAA arms. Thus, the stability of its mixed solution with PEO 113 -b-PQDMA 48 should be ascribed to the stabilization effect of the PQDMA block. The formed colloidal particles again possessed an ''onion-like'' microstructure with a PDVB microgel core, an inner layer of the PEO/PMAA hydrogen bonded complexes, and the PQDMA outer corona.…”

“…Figure 5. hR h i as a function of solution pH for the mixed solution of (PEO) n -PDVB-(PMAA) n and PEO 113 -b-PQDMA 48 . The weight fraction of PEO 113 -b-PQDMA 48 was 0.6 and the total polymer concentration was 0.5 g Á L À1 .…”