Synthesis and derivatization of epoxy-functional sterically-stabilized diblock copolymer spheres in non-polar media: does the spatial location of the epoxy groups matter?

Abstract

Epoxy-functional sterically-stabilized diblock copolymer spherical nanoparticles were synthesized via polymerization-induced self-assembly (PISA) in mineral oil. Epoxy groups were located either (i) in the nanoparticle cores or (ii) within the steric stabilizer chains. For the first system, reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization of glycidyl methacrylate (GlyMA) was conducted using a poly(lauryl methacrylate) (PLMA₆₃) precursor. The second system involved statistical copolymerization of GlyMA with lauryl methacrylate to produce a P(LMA₅₀-stat-GlyMA₉) precursor followed by chain extension using methyl methacrylate (MMA). ¹H NMR studies and THF GPC analysis indicated that high monomer conversions (≥ 95%) and narrow molecular weight distributions (M_w/M_n ≤ 1.17) were obtained for both formulations. Dynamic light scattering indicated hydrodynamic diameters of 26 nm and 28 nm for P(LMA₅₀-stat-GlyMA₉)-PMMA₆₇ and PLMA₆₃-PGlyMA₈₉ spheres, respectively. Transmission electron microscopy studies confirmed a well-defined spherical morphology in each case. Post-polymerization modification of these spherical nanoparticles was examined by reacting the epoxy groups with benzylamine. For the PLMA₆₃-PGlyMA₈₉ spheres, an [amine]/[epoxy] molar ratio of unity was sufficient to react all the epoxy groups. In contrast, the P(LMA₅₀-stat-GlyMA₉)-PMMA₆₇ spheres required a fifty-fold excess of benzylamine for complete reaction. Furthermore, epoxy ring-opening reactions were conducted using either a trace amount of water or 50% v/v aqueous acetic acid at 110 °C. The extent of reaction was assessed using ¹H NMR spectroscopy and THF GPC for the P(LMA₅₀-stat-GlyMA₉)-PMMA₆₇ spheres and by FT-IR spectroscopy for the core-crosslinked PLMA₆₃-PGlyMA₈₉ spheres.