Features of Polymerization of Methyl Methacrylate using a Photocatalyst—the Complex Oxide RbTe1.5W0.5O6

Lyudmila Semenycheva,Tatiana Belaya,Diana Fukina,Julia Matkivskaya,Andrey Koryagin,Victoria Chasova,Alexandra Grigoreva,Yuri Kursky,Evgeny Suleimanov

doi:10.1007/s10904-021-02054-6

Abstract

Radical polymerization of methyl methacrylate in an aqueous emulsion was carried out using the complex oxide RbTe1.5W0.5O6 as a photoinitiator under visible light irradiation with λ = 400–700 nm. Study of the polymerization process and reaction products using methods of physical and chemical analysis (GPC, IR, NMR, etc.) has shown that there are several directions of monomer transformations at the same time. Polymethyl methacrylate with Mn ~ 140–145 kDa, produced in the organic phase, is a result of polymerization initiation by a hydroxyl radical formed due to complex transformations of electron–hole pairs during photocatalyst irradiation. Moreover, the interaction of the hydroxyl radical with OH-groups on the complex oxide RbTe1.5W0.5O6 surface and the subsequent formation of oxygen-centered radicals lead to grafting polymer macromolecules on the photocatalyst surface. In addition, methyl methacrylate is able to oxidize to a cyclic dimer with terminal double bonds and form a polymer with cyclic dimer links due to coordination by double bonds on the RbTe1.5W0.5O6 surface. The high activity of the hydroxyl radical allows to obtain the graft copolymer PMMA-pectin by grafting the polymer product on the surface of the natural polymer-pectin. Comparison of the sponge morphology of the graft copolymer PMMA-pectin and the initial pectin samples using the scanning electron microscopy has shown a noticeable difference in their structural and topological organization. It is especially interesting in terms of studying the properties of the graft copolymer as a material for the scaffolds.

Highlights

The creation of new effective photocatalysts attracts the attention of scientists as a direction of research involving waste-free technologies
The formation of an active hydroxyl radical in the reaction system is of interest for organic synthesis, primarily for the production of new polymer materials without material initiators fragments with organic nature [9, 11]
It was found that several directions of monomer transformations occur simultaneously in the reaction mixture as a result of radical polymerization of methylmethacrylate in an aqueous emulsion using the complex oxide RbTe1.5W0.5O6 as a photoinitiator under visible light irradiation λ= 400-700 nm

Summary

Introduction

The creation of new effective photocatalysts attracts the attention of scientists as a direction of research involving waste-free technologies. The photocatalytic water splitting with the formation of hydrogen and organic compounds decomposition in aqueous solutions to carbon dioxide and water suggest either direct interaction with reactive hydroxyl radicals formed as a result of complex transformations of electron-hole pairs, or with oxidizing centers on the photocatalyst surface [1-10]. The formation of an active hydroxyl radical in the reaction system is of interest for organic synthesis, primarily for the production of new polymer materials without material initiators fragments with organic nature [9, 11]. The complex oxide RbTe1.5W0.5O6 with βpyrochlore structure has been synthesized recently. A detailed study of its electronic structure showed the fundamental possibility of using it as a photocatalyst under visible light irradiation (λ= 400-700 nm), and the photocatalytic oxidizing of methylene blue on the RbTe1.5W0.5O6 surface has been experimentally confirmed [7, 12]

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