One pot synthesis of thiol-functional nanoparticles

Abstract

Polysorbate 80 (PS80) was reacted with 3-mercaptopropyl trimethoxysilane (SiSH) via a photoinitiated thiol–ene reaction. The conjugate was then mixed with SiSH and water to form uniform thiol-functional nanoparticles (TFNs) approximately 22 nm in diameter. Aqueous TFN solutions (20 wt% solids) can be used directly to conduct thiol–ene/thiol-Michael reactions or concentrated by heating at 60 °C to 50 wt% solids. The large number of thiol residues per particle also provides a convenient route for changing the physical or chemical properties of the particles. This is easily accomplished by directly reacting the TFNs with monofucntional alkenes under photochemical initiation. These reactions usually proceed to quantitative conversion within four to eight hours depending on the nature of the alkene and the photoinitator. Initital crosslinking experiments of TFNS with commercial alkene crosslinking agent PEGDMA (poly(ethylene glycol)dimethacrylate) showed improved cure rates when compared to the crosslinker of PEGDMA by itself. Using these results, TFN resins employing several commercial crosslinkers were synthesized and printed on a commercial DLP printer. PEGDMA resins produced opaque prints with poor strength while ACMAC (3-(acryloyloxy)-2-hydroxypropyl methacrylate) produced several translucent prints with good strength and stiffness. The addition of TFNs to commercial 3D printing resin resulted in a significant rate enhancement allowing digital light projection (DLP) exposure times of 0.5 seconds per layer. This simple scalable one-pot process produces multifunctional thiols that are soluble in both aqueous and organic solvents without the need for organic solvents or purification.