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

Abstract

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-<i>block</i>-styrene) micelles and via <i>one-pot</i> photoacid-catalyzed micelle formation and siloxane cross-linking of poly(4-<i>tert</i>-butoxystyrene-<i>block</i>-styrene). The <i>multistep</i> 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.