Amphiphilic thermoresponsive copolymer bottlebrushes: synthesis, characterization, and study of their self-assembly into flower-like micelles

Abstract

Amphiphilic thermoresponsive copolymer bottlebrushes based on methoxy oligo(ethylene glycol)7 methacrylate and alkoxy(C12–C14) oligo(ethylene glycol)6 methacrylate have been successfully synthesized via RAFT and conventional free-radical polymerization in toluene. The thermoresponsive behavior of the copolymers in dilute aqueous solutions was studied by turbidimetry and laser light scattering. In water, the copolymer brushes form flower-like micelles with a hydrophobic core consisting of a polymer backbone and alkyl(C12–C14) groups and poly(ethylene glycol) linear chains and loops forming a hydrophilic shell. The size and aggregation number of the micelles and the cloud point of solutions were found to depend on the copolymer composition and chain length, as well as on the synthesis method. The conditions needed for the formation of uni- and multimolecular micelles were determined. Fluorescence techniques were used to determine the CMC of the copolymers and the drug loading capacity of the micelles using pyrene as a model hydrophobic drug. Amphiphilic thermoresponsive copolymer bottlebrushes based on methoxy oligo(ethylene glycol) methacrylate (MOEGM) and alkoxy(C12-C14) oligo(ethylene glycol) methacrylate (DOEGM) have been synthesized via RAFT and conventional free-radical polymerization in toluene. In water, these copolymer brushes form flower-like micelles with a hydrophobic core consisting of a polymer backbone and alkyl(C12–C14) groups and poly(ethylene glycol) linear chains and loops forming a hydrophilic shell. The size and aggregation number of the micelles depend on the copolymer composition and chain length, as well as on the synthesis method.