Synthesis of a Epoxy Based Copolymer via Ambient Temperature RAFT Copolymerization of n-Butyl Acrylate and Glycidyl Methacrylate under Mild UV-Vis Radiation

Abstract: The epoxy based (meth)acrylate copolymers present various industrial applications such as coatings, adhesives and enzyme immobilization. The synthesis of well-defined (meth)acrylate copolymers with control over functionalities has attracted increased interest. It is the purpose of this paper to prepare the well-defined epoxy based copolymers by ambient temperature reversible addition fragmentation chain transfer (RAFT) radical copolymerization. RAFT-synthesized polymers with thiocarbonylthio groups may be colored, may also, in some cases, release an odor. Thus, removing thiocarbonylthio groups in copolymers is another purpose of the paper.For this purpose, ambient temperature RAFT radical copolymerization of n-butyl acrylate(nBA) and glycidyl methacrylate(GMA) was performed with a S-1-dodecyl- S′-(α,α′-dimethyl-α′′-acetic acid) trithiocarbonate (DDMAT) chain transfer agent and a (2,4,6-trimethylbenzoyl) diphenylphosphine oxide (TPO) photoinitiator under mild UV-vis radiation. Semilogarithimic plots of total monomer conversion vs time were nearly linear. It was observed that the copolymerization displayed an increased rate with increased nBA content in the initial monomer feed. Plots of Mn vs monomer conversion were linear, and polydispersity decreased with increasing monomer conversion. The copolymerization is typical controlled radical polymerization when the GMA concentration was equal to or below 50 mol %.The reactivity ratios of monomers (rGMA = 1.596, rnBA = 0.422) for the copolymerization were calculated by the extended Kelen-Tüd·s method. The studies of copolymer composition displayed that the content of GMA in the macromolecular chain decreases as the conversion increases. The cumulative compositions of the copolymers were calculated and were found to agree well with predicted values. The studies of copolymer sequence distribution using 13C NMR spectra showed that the epoxy groups were randomly incorporated along copolymer chains when the GMA concentration was equal to or below 20 mol %.The removal of thiocarbonylthio groups from RAFT-synthesized polymers by radical-induced reduction has been studied. The thiocarbonylthio groups are removed quickly and efficiently by using photoinitiator under UV-vis radiation, while molecular weight and polydispersity of copolymer did not chang obviously…
Key words: Epoxy based copolymers; Ambient temperature RAFT copolymerization; UV-Vis radiation; Thiocarbonylthio end group removal; Radical-induced reduction

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