Nanoparticles bearing germanium based photoinitiators at their surface: Preparation and use in grafting-from photopolymerization reactions

In recent decades, there has been a growing interest in surface modifications utilizing “grafting-from” techniques within both industrial and academic fields. Among others, this technology continues to drive innovation in biomedicine, enabling the design and fabrication of advanced materials and devices with tailored properties for a wide range of applications, from regenerative medicine and drug delivery to diagnostics and therapeutics. This strategy relies on the covalent attachment of (photo)initiating species to surfaces. The coupled initiators are exploited to produce reactive sites such as radicals upon exposure to heat or light. Subsequently, polymerization reactions are induced, leading to surface coupled polymer brushes. In order to provide new perspectives in surface modification techniques, we present a novel and unique method for producing mesoporous organic/inorganic hybrid nanoparticles via the “grafting-from” method. This was accomplished by immobilizing a novel, low-toxic and visible light sensitive photoinitiator (based on triacylgermanium moieties) onto silica nanoparticles. Surface-initiated photopolymerizations of styrene and acrylate monomers were conducted to produce polymer shells on the surface of the nanoparticles. The grafted layers had a thickness in the range of 6–12 nm. Furthermore, the polymer grafting density is discussed in detail ranging between 0.17 and 0.23 chains per square nanometer.