Organic–Inorganic Hybrid Nanoparticles via Photoinduced Micellation and Siloxane Core Cross-Linking of Stimuli-Responsive Copolymers

Photoacid-induced siloxane cross-linking of stimuli-responsive copolymer micelles allows the synthesis of well-defined organic–inorganic hybrid nanoparticles. Two conceptually different synthetic approaches are presented, both via photoinduced cross-linking of poly(4-hydroxystyrene-block-styrene) micelles and via one-pot photoacid-catalyzed micelle formation and siloxane cross-linking of poly(4-tert-butoxystyrene-block-styrene). The multistep synthetic route showed intermicellar cross-linking leading to agglomerates. In contrast to this, the formation of the nanoparticles via the one-pot synthesis yielded well-defined structures. The use of different siloxane cross-linking agents and their effects on the properties of the cross-linked micellar structures have been evaluated. Scanning electron microscopy and differential scanning calorimetry indicate rigid core cross-linked nanoparticles. Their size, molar mass, and swelling behavior were analyzed by dynamic and static light scattering. Cyclic siloxane cross-linking agents lead to residual CC double bonds within the nanoparticle core that allow postsynthetic modification by, e.g., thiol–ene click reactions.