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RISS 인기검색어
- 검색키워드
- 저자 : Igor Fedushkin (검색결과 2 건)
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Dmitrii Ludin,Yulia Voitovich,Evgenia Salomatina,Yulia Kuznetsova,Ivan Grishin,Igor Fedushkin,Sergey Zaitsev 한국고분자학회 2020 Macromolecular Research Vol.28 No.9
We report a reversible-deactivation radical copolymerization of styrene and methyl acrylate in the presence of tributylborane and different p-quinones. p-Quinones, such as 1,4-naphthoquinone, 2,3-dimethyl-1,4-benzoquinone, 2,5-ditert- 1,4-butylbenzoquinone, and duroquinone, with addition of a catalytic amount of tributylborane, allow for the control over styrene/methyl acrylate copolymerization. The process proceeds in a controlled manner via a reversible homolytic dissociation of the active macromolecules with terminal aryloxyboron-groups. The rate of styrene/methyl acrylate copolymerization depends on the inhibition constants of quinones. The molecular weight and molecular weight distribution of copolymers are directly dependent on the inhibitory abilities of the quinones. 1,4-Naphthoquinone and 2,3-dimethyl-1,4-benzoquinone act as the most effective mediators of chain propagation. Matrixassisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) results showed that the macromolecules contained internal fragments of p-quinone. Also, of the terminal aryloxyboron-groups were detected in the mass spectra. On realization of the “living” mechanism of copolymerization, the structure of copolymers obtained at high conversions can be considered as similar to the gradient structure. Stereo-regularity of the copolymers differed from the conventional radical copolymerization. The glass-transition temperature (Tg) of the gradient copolymer differed from Tg of the random compositional heterogeneous copolymer. The effect of the macromolecular structure on the mechanical properties of the copolymers was studied.
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Dmitrii V. Ludin,Nadezhda V. Illarionova,Ekaterina V. Bobrina,Konstantin A. Kozhanov,Ivan D. Grishin,Sergey D. Zaitsev,Igor L. Fedushkin 한국고분자학회 2023 Macromolecular Research Vol.31 No.3
Polymerization of styrene with tributylborane in the presence of various p-quinones (2,3-dimethyl-1,4-benzoquinone, 1,4-naphthoquinone, menadione, duroquinone, 2,5-di-tert-butyl-1,4-benzoquinone) has been investigated. It was found that in spite of dual nature of p-quinone and the presence of tributylborane in the initial mixture, the semi-quinone macroradical is capable to “chain regeneration”. Neither solvent introduction nor use of a more reactive triethylborane affects this process. The insensitivity of this reaction to external conditions may be caused by the cell effect. For some p-quinones in the presence of tributylborane, the realization of reversible-deactivation radical polymerization is observed. Mechanism of the chain termination reactions was established by the MALDI-TOF technique. It consists of reversible inhibition causing the formation of active macromolecules as well as irreversible inhibition causing the formation of “dead” macromolecules. The ratio of these directions depends on the relative reactivity of p-quinone (kz/kp). The higher is kz/kp, the lower is the probability of irreversible inhibition. Polymers obtained in the presence of the tributylborane/p-quinone system can re-initiate polymerization. Post-polymers with distinct molecular weight characteristics (Đ = 1.12 – 1.19) were obtained during this synthesis. Only polystyrene macro-radicals are formed during polymerization re-initiation. This fact has been proven by ESR spectroscopy. The macroinitiator polymers isolated at the initial conversions have the same reactivity regardless of the p-quinone nature. The linear dependence of Mn with conversion, the polydispersity lessening, and the constant concentration of macro-radicals indicate realization of reversible-deactivation radical polymerization.
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