Separable and recyclable SBA-15 based catalyst for metal-free ATRP

The aminoated SBA-15 (SBA-15-NH2) was obtained by the condensation reaction between the hydroxyl group on the surface of SBA-15 and the ethoxy group of 3-aminopropyl triethoxysilane (KH550) coupling agent. And then the fluorescein acyl chloride (Flu-Cl) or rhodamine B acyl chloride (RB-Cl) was loaded onto SBA-15 surface to gain two kinds of SBA-15 based catalysts (SBA-15-Flu and SBA-15-RB) via the reaction between the amino group of SBA-15-NH2 and the acyl chloride group of Flu-Cl or RB-Cl. The metal-free ATRP of methyl methacrylate (MMA) was carried out under 365 nm UV light using SBA-15 based catalyst as photocatalyst, and ethyl 2-bro-moisobutyrate (EBIB) as initiator. The structure of the two SBA-15 based catalysts was confirmed by fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and thermogravimetry analysis (TGA). The morphology and surface area of SBA-15 before and after modification were observed by scanning electron microscopy (SEM) and brunauer emmett teller (BET) respec-tively. The results showed that Flu-Cl and RB-Cl have been successfully loaded onto SBA-15 surface. Gel permeation chromatograph (GPC) and kinetic experiments illustrated the polymerization process was control-lable and the molecular weight distribution was relatively narrow, which conforms to the characteristics of living radical polymerizations. After polymerization, the SBA-15 based photocatalyst was separated by simple centri-fugation and recycled three or four times for metal-free ATRP. In these cyclic catalytic processes, the separated SBA-15 based photocatalyst exhibited excellent catalytic effect, the polymerization product is pure and has no residual catalyst.

Automated summary

The aminoated SBA-15 (SBA-15-NH2) was obtained by condensing the hydroxyl group on the surface of SBA-15 with the ethoxy group of 3-aminopropyl triethoxysilane (KH550) coupling agent. Two types of SBA-15-based catalysts (SBA-15-Flu and SBA-15-RB) were then created by loading fluorescein acyl chloride (Flu-Cl) or rhodamine B acyl chloride (RB-Cl) onto the SBA-15 surface. These catalysts were used in the metal-free ATRP of methyl methacrylate (MMA) under 365 nm UV light. The structure of the catalysts was confirmed using various spectroscopy techniques, and their catalytic performance was evaluated through polymerization experiments.