Poly(methacrylic acid)-based AB and ABC block copolymer nano-objects prepared via RAFT alcoholic dispersion polymerization
Résumé
A series of well-defined amphiphilic poly(methacrylic acid)-poly(benzyl methacrylate) (PMAA-PBzMA) diblock copolymers are synthesized via polymerization-induced self-assembly using an alcoholic dispersion polymerization formulation. Chain growth is mediated via reversible addition-fragmentation chain transfer polymerization (RAFT) chemistry using a trithiocarbonate-based chain transfer agent (CTA) at 70 degrees C. The poly(methacrylic acid) block is soluble in ethanol and acts as a steric stabilizer for the growing insoluble PBzMA chains, resulting in the in situ generation of diblock copolymer nano-objects in the form of spheres, worms or vesicles, depending on the precise reaction conditions. Copolymer morphologies can be covalently stabilized via cross-linking to prevent their dissociation when transferred into aqueous solution, which leads to the formation of highly anionic nano-objects due to ionization of the PMAA stabilizer chains. ABC triblock copolymer nanoparticles can also be prepared using this approach, where the third block is based on the semi-fluorinated monomer, 2,2,2-trifluoroethyl methacrylate (TFEMA). GPC studies confirm that chain extension is efficient and high TFEMA conversions can be achieved. Microphase separation between the mutually incompatible PBzMA and semi-fluorinated PTFEMA core-forming blocks occurs, producing a range of remarkably complex semi-fluorinated triblock copolymer morphologies.