Diblock Copolymer Nanoparticles Act as Nanoreactors for the Synthesis of Sterically‐Stabilized Inorganic Oxide Particles in Non‐polar Media

ABSTRACT Well‐defined diblock copolymer nanoparticles are prepared via reversible addition‐fragmentation chain transfer (RAFT) dispersion polymerization of 2‐hydroxyethyl methacrylate (HEMA) in a poly(α‐olefin) oil at 90°C using a poly(lauryl methacrylate) (PLMA) precursor. The PHEMA cores of these nanoparticles are subsequently swollen with up to 30% w/w aqueous 0.3 M HCl based on the PHEMA mass and then used as nanoreactors for the in situ synthesis of silica or titania using either tetraethyl orthosilicate (TEOS) or titanium tert ‐butoxide, respectively. The PLMA‐PHEMA nanoparticles are characterized by transmission electron microscopy, dynamic light scattering (DLS), and small‐angle x‐ray scattering (SAXS). The former technique indicates that core‐swelling leads to a subtle change in copolymer morphology from pseudo‐spherical to perfectly spherical nanoparticles. DLS and SAXS confirm the formation of near‐monodisperse nanoparticles of 92–117 nm diameter with colloidal stability being retained after the nanoreactor syntheses. For the silicified nanoparticles, time‐resolved turbidimetry and SAXS studies suggest a reaction timescale of around 50 min at 25°C. In this case, the final nanoparticle dispersion is highly transparent, whereas the corresponding titania‐loaded nanoparticles produce a highly turbid dispersion. Thermogravimetric analyses indicate silica and titania mass loadings of 17% and 21%, respectively. In both cases the inorganic phase is amorphous rather than crystalline.