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1.
V. V. Burlakov A. V. Letov P. Arndt W. Baumann A. Spannenberg Ch. Fischer L. I. Strunkina M. Kh. Minacheva Ya. S. Vygodskii U. Rosenthal V. B. Shur 《Journal of molecular catalysis. A, Chemical》2003,200(1-2):63-67
Zwitterionic titanoxanes {Cp[η5-C5H4B(C6F5)3]Ti}2O (I) and {(η5-iPrC5H4)[η5-1,3-iPrC5H3B(C6F5)3]Ti}2O (II), which contain two positively charged Ti(IV) centres in the molecule, are able to catalyse the ring-opening polymerization of -caprolactone (-CL) in toluene solution and in bulk. The process proceeds with a noticeable rate even at room temperature and accelerates strongly on raising the temperature to 60 °C. The best results have been obtained on carrying out the reaction in bulk. Under these conditions, the use of I as a catalyst (-CL:I = 1000:1) gives at 60 °C close to quantitative yield of poly--CL with the molecular mass of 197 000. An increase in the -CL:I ratio to 6000:1 increases the molecular mass of poly--CL to 530 000. Tetrahydrofuran (THF) is also polymerized under the action of I albeit with a lesser rate. However, the molecular mass of the resulting poly-THF can reach rather big values under optimal conditions (up to 217 000 at 20 °C and the THF:I ratio of 770:1). A rise in the reaction temperature from 20 to 60 °C results here to a decrease in the efficiency of the process. Titanoxane II is close to I in its catalytic activity in the -CL polymerization but it is much less active in the polymerization of THF. Propylene oxide (PO), in contrast to -CL and THF, gives with I only liquid oligomers in wide temperature and PO:I molar ratio ranges (−30 to +20 °C, PO:I = 500–2000:1). γ-Butyrolactone and 1-methyl-2-pyrrolidone are not polymerized under the action of I at room temperature. The reactions found are the first examples of catalysis of the cationic ring-opening polymerization by zwitterionic metallocenes of the group IVB metals. 相似文献
2.
A. A. Bezrukova V. S. Khandkarova P. V. Petrovskii A. Z. Rubezhov Ya. S. Vygodskii K. P. Butin T. V. Magdesieva G. A. Pirogova 《Russian Chemical Bulletin》1995,44(5):941-945
Binuclear RhIII and RuII complexes of the [M1-CN-M2]+BF
4
–
(M1 and/or M2 are (5-Cp)(3-C3H5)Rh and (6-C6H6)(3-C3H5)Ru) type, heteronuclear organometallic compound (5-Cp)(3-C3H5)RhCNPd(3-C3H5)Cl, and mononuclear RhIII and RuII complexes [(3-C3H5)LM(MeCN)]+
BF4
–
(M = Rh, L = 5-Cp; M = Ru, L = 6-C6H6) were synthesized. An electrochemical study of these compounds in solutions demonstrates that the bond between the bridged CN ligand and the metal atoms is rather strong, and there is no dissociation into mononuclear fragments in solutions. The kinetics of the reaction of [(5-Cp)(3-C3H5)Rh(MeCN)]+
BF4
–
with halide ions was studied by electrochemical methods. The ligand exchange proceeds by a bimolecular dissociative-exchange mechanism.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 968–973, May, 1995. 相似文献
3.
Said-Galiev E. E. Keshtov M. L. Khokhlov A. R. Vygodskii Ya. S. Dvorikova R. A. Belomoina N. M. Bulycheva E. G. 《Russian Chemical Bulletin》2020,69(6):1035-1053
Russian Chemical Bulletin - The achievements of polycondensation in supercritical carbon dioxide over the past 20 years are considered. The contribution of the A. N. Nesmeyanov Institute of... 相似文献
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O. N. Zabegaeva D. A. Sapozhnikov A. V. Krestinin V. A. Kotel’nikov B. A. Baiminov Ya. S. Vygodskii 《Polymer Science Series B》2016,58(1):54-60
The anionic polymerization of ε-caprolactam in the presence of single-walled carbon nanotubes with grafted acyllactam groups or polyimide macromolecules is performed. It is shown that the polymerization of ε-caprolactam slows down with an increase in the filler concentration. The introduction of 0.01 wt % nanotubes with polyimide fragments into polycaproamide leads to a 25% increase in the compressive modulus. In this case, the Izod impact strength is 10 kJ/m2, that is, 150% higher than that for an unfilled polycaproamide or polycaproamide containing other types of nanotubes. 相似文献
7.
T. V. Volkova O. N. Pashkova M. N. Il’ina E. M. Belavtseva Ya. S. Vygodskii 《Bulletin of the Russian Academy of Sciences: Physics》2008,72(11):1490-1492
It is established that graft copolymers of polycaproamide with 3–5 wt % of polyimide exhibit a rubber-like elasticity region above the polycaproamide melting temperature. Polycaproamide modification with polyimide increases the polymer thermal resistance, glass-transition temperature, and impact strength. Scanning electron microscopy revealed that the supramolecular organization of polycaproamide is similar to that of its copolymers with polyimide but differs in the spherulite size. 相似文献
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The kinetics of N-phenylphthalamic acid and of N-phenylphthalimide hydrolysis in aqueous solutions of sulfuric acid has been studied. A reaction mechanism is proposed implying that unreactive forms of the reactant appear by protonization of the amide bond at the carbonyl oxygen and by dissociation of the o-carboxyl group (N-phenylphthalamic acid). Attack of the nonprotonized amide bond by the hydroxonium ion is suggested to be the rate-limiting step. 相似文献
10.