Controllable surface-initiated metal-free atom transfer radical polymerization of methyl methacrylate on mesoporous SBA-15 via reductive quenching

Abstract

The surface-initiated metal-free atom transfer radical polymerization (ATRP) solution polymerization of methyl methacrylate was carried out for the first time on the basis of the reductive quenching mechanism. In this study, the 2-bromoisobutyryl bromide (BiBB) was anchored on the surface of self-synthesized rod-like mesoporous material SBA-15 as the initiator, with the commercially available organic dye fluorescein (FL) as photocatalyst and triethylamine (TEA) as electron donor under the irradiation of blue lamp. The obtained composites and polymers were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, N2 adsorption/desorption measurements, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and gel permeation chromatography. The results demonstrated that the ordered mesoporous structure of SBA-15 was not disrupted after the polymerization. With an increase in illumination time, the grafting amount and the number average molecular weight of poly(methyl methacrylate) (PMMA) on the surface of SBA-15 linearly increased, and the molecular weight distribution (Đ) widened. PMMA with a relatively narrow Đ value was obtained after polymerization for 10 h (1.47). The increase in the grafting amount and molecular weight after chain extension confirmed the chain end functionality of PMMA grafted on SBA-15.