Self-Assembly of Amphiphilic Random Copolyacrylamides into Uniform and Necklace Micelles in Water

Abstract

Amphiphilic random copolyacrylamides bearing hydrophilic poly(ethylene glycol) (PEG) and hydrophobic dodecyl pendants induce precision self-assembly to produce quite small uniform and/or necklace micelles (≈10 nm) in water. The size, structure, and thermoresponsive properties of the micelles are controlled by the primary structure (composition and chain length) of the copolymers. For this, random copolymers with different composition, chain length, and molecular weight distribution are synthesized by iron-catalyzed living or free radical copolymerization of PEG acrylamide and dodecyl acrylamide (DAAm). The copolymers with controlled molecular weight (degree of polymerization: ≈40) intermolecularly self-assemble and/or self-fold to form uniform (multichain or unimer) micelles in water; the size increases with increasing hydrophobic DAAm content (19–57 mol%: Mw = 43 900–191 000). In contrast, random copolymers with relatively small DAAm content (<35 mol%) and broad molecular weight distribution provide both uniform and necklace micelles in water.