Haiyong Huang

Shell cross-linked polymer micelles: stabilized assemblies with great versatility and potential

Abstract Shell cross-linked polymer micelles have been introduced within the past 3 years, and they have already demonstrated great promise as robust nanostructured core-shell nanospheres. The formation of cross-links throughout the shell of polymer micelles offers stability to the nanostructured assemblies, by providing reinforcement to the weak interactions that facilitate polymer micelle existence. Cross-linking can be accomplished by direct reaction between the chain segments located within the polymer micelle shell, or via addition of multi-functional cross-linking reagents. The dimensions, composition, and properties of each of the domains of the polymer micelles can be controlled by selection of diblock copolymer composition, conditions for polymer micelle assembly, and chemistry used for cross-linking. An overview of each of the examples of SCK nanospheres currently known is presented here.

Amphiphilic core–shell nanospheres obtained by intramicellar shell crosslinking of polymer micelles with poly(ethylene oxide) linkers

Intramicellar crosslinking of the polymer chains within the shells of polystyrene-b-poly(acrylic acid) micelles by reaction with difunctional poly(ethylene oxide) afforded unimolecular amphiphilic core–shell nanospheres (50 nm hydrodynamic radius); the resulting surface hydrogel layer gives an approximate fivefold increase of particle volume from the dry state to aqueous solution.

Location of Fluorotryptophan Sequestered in an Amphiphilic Nanoparticle by Rotational-Echo Double-Resonance NMR

Rotational-echo double-resonance (REDOR) 13C NMR spectra (with 19F dephasing) have been obtained of 6-fluorotryptophan complexed by a polymeric amphiphilic nanosphere consisting of a polystyrene core covalently attached to a poly(acrylic acid)-polyacrylamide shell. The REDOR spectra show that aromatic carbons from the polystyrene core and oxygenated carbons in the poly(acrylic acid)-polyacrylamide shell are both proximate to the 19F of 6-fluorotryptophan. Molecular modeling restrained by distances inferred from the REDOR spectra suggests that all of the 6-fluorotryptophans are in the shell but within 10 A of the core-shell interface.