RAFT aqueous dispersion polymerization yields poly(ethylene glycol)-based diblock copolymer nano-objects with...

Area of Science:

• Polymer Chemistry
• Materials Science
• Nanotechnology

Background:

• Poly(ethylene glycol) (PEG) macromolecular chain transfer agents (macro-CTAs) are crucial for controlled polymer synthesis.
• Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization enables the synthesis of well-defined polymers.
• Aqueous dispersion polymerization is a green chemistry approach for nanoparticle synthesis.

Purpose of the Study:

• To synthesize a novel PEGylated dithiobenzoate macro-CTA for RAFT polymerization.
• To investigate the synthesis of poly(2-hydroxypropyl methacrylate) (PHPMA) based diblock copolymers using RAFT.
• To control the self-assembly of PEG-PHPMA diblock copolymers into various nanostructures.

Main Methods:

• Three-step synthesis of PEG113-dithiobenzoate macro-CTA.
• RAFT aqueous dispersion polymerization of HPMA using the synthesized macro-CTA.
• Characterization using NMR, GPC, DLS, TEM, and SAXS.

Main Results:

• High yield (>95%) and functionality (>97%) of PEG113-dithiobenzoate macro-CTA.
• Controlled polymerization of HPMA with low polydispersity (M(w)/M(n) < 1.25) and good blocking efficiency.
• Tunable self-assembly into spheres, worms, and vesicles up to 17.5% solids.
• Observation of oligolamellar vesicles with approximately three membranes at 20% solids.
• Construction of a PEG113-PHPMA(x) phase diagram for reproducible morphology control.

Conclusions:

• A robust RAFT PISA formulation for synthesizing PEGylated diblock copolymer nano-objects was developed.
• The method allows for precise control over nanoparticle morphology (spheres, worms, vesicles, oligolamellar vesicles).
• The developed formulation is suitable for the rational and efficient synthesis of biocompatible, thermo-responsive nanostructures for biomedical applications.