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Direct Thiol-Ene Photocoating of Polyorganosiloxane Microparticles


Schlaad,  Helmut
Helmut Schlaad, Kolloidchemie, Max Planck Institute of Colloids and Interfaces, Max Planck Society;

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Kuttner, C., Maier, P. C., Kunert, C., Schlaad, H., & Fery, A. (2013). Direct Thiol-Ene Photocoating of Polyorganosiloxane Microparticles. LANGMUIR, 29(52), 16119-16126. doi:10.1021/1a4039864.

This work presents the modification of polyorganosiloxane microparticles by surface-initiated thiol-ene photochemistry. By this photocoating, we prepared different core/shell particles with a polymeric shell within narrow size distributions (PDI = 0.041-0.12). As core particle, we used highly monodisperse spherical polyorganosiloxane particles prepared from (3-mercaptopropyl)trimethoxysilane (MPTMS) with a radius of 0.49 mu m. We utilize the high surface coverage of mercaptopropyl functions to generate surface-localized radicals upon irradiation with UVA-light without additional photoinitiator The continuous generation of radicals was followed by a dye degradation experiment (UV/vis spectroscopy). Surface-localized radicals were used as copolymer anchoring sites ("graftingonto" deposition of different PB-b-PS diblock copolymers) and polymerization initiators ("grafting-from" polymerization of PS). Photocoated particles were characterized for their morphology (SEM, TEM), size, and size distribution (DLS). For PS-coated particles, the polymer content (up to 24% in 24 h) was controlled by the polymerization time upon UVA exposure. The coating thickness was evaluated by thermogravimetric analysis (TGA) using a simple analytical core/shell model. Raman spectroscopy was applied to directly follow the time-dependent consumption of thiols by photoinitiation.