The polymerization of cyclohexene oxide was investigated with a new catalyst system of Al(acac)3- silanol compounds. Catalyst activity varied with the ratio of silanol/Al(acac)3 and the structure of silanol compounds. Catalyst deactivation appeared to be caused by self-condensation of silanol and the addition of silanol to the epoxy ring. Polymer structure was investigated by 13C-NMR spectroscopy and x-ray diffraction. The mechanism of the polymerization appears to be cationic. 相似文献
A new catalyst system (Ph3SiCOPh-aluminum complex-alcohol) was investigated for photopolymerization of cyclohexene oxide. Polymer conversion and molecular weight increased with polymerization time. When a Ph3SiCOPh-Al (n-Praa)3-alcohol catalyst system was used the catalyst activity decreased, depending on the alcohol: i-PrOH > n-PrOH > i-BuOH > MeOH > t-BuOH > H2O. When the Ph3SiCOPh-Al complex-i-PrOH catalyst system was used the catalyst activity decreased, depending on the ligand of the Al complex: ß-ketoester > orthocarbonyl phenol > ß-diketone. Benzophenone derivatives were effective for catalyst activation as a photosensitizer. 相似文献
Polymerization of cyclohexene oxide, especially the catalytic activity influenced by silanol structure, was examined by using an Al(acac)3–silanol compound catalyst. The catalytic activity increased as the acidity of silanol increased. It was prolonged by sterically hindered silanol compounds which prevented the silanol from self-condensation and from joining with the epoxide. In addition, the greater catalytic activity produced by intramolecular hydrogen-bonding silanol compounds is explained by the polymer effect. 相似文献
The polymerization of cyclohexene oxide with Al(acac)3-silanol catalyst supported by zeolite and porous silica has been investigated. Cyclohexene oxide was also polymerized to a lesser extent by a zeolite-silanol catalyst and an Al(acac)3-silica gel catalyst. The catalytic activity of the zeolite-silanol system varied with the zeolite pore size. The catalytic activity of the Al(acac)3-silanol system was enhanced by supporting the catalyst with porous silica or zeolite. The Al(acac)3-silanol catalyst supported by zeolite was especially effective in increasing polymer conversion and molecular weight. Catalytic activity increased with increasing chemical interaction between silanol and porous silica. The molecular weight of the polymers with these catalysts increased in the order zeolite-silanol> zeolite-Al(acac)3-silanol >Al(acac)3-silanol ≈ Al(acac)3-silanol supported by porous silica>Al(acac)3-silica gel. 相似文献
o-Nitrobenzyl triphenylsilyl ehther/aluminum compound has been previously shown by the authors to act as catalyst in the photopolymerization of epoxides. The dependence of the structure of the silyl ether on the catalyst activity was examined. There were two steps in the photopolymerization. The first step (“Step 1”) is photodecomposition of the silyl ether to silanol. The second step (“Step 2”) is the initiation of polymerization by silanol and the aluminum compound. The introduction of an electron withdrawing group, Cl, CF3, on the benzene ring bonded to Si made the quantum yield of Step 1 low, however, the rate of Step 2 was increased. The low quantum yield of Step 1 was explained in terms of the rate of electron transfer that is controlled by the relative electron density between the CH2 and NO2 in the o-nitrobenzyl group. The acceleration of Step 2 was explained in terms of an increase in silanol acidity that was promoted by the introduction of an electron withdrawing group. The overall rate of the photopolymerizatiol depends to a greater degree on the rate of Step 2 than on that of Step 1. 相似文献
The polymerization of N-methylmethacrylamide (NMMAm) with azobisisobutyronitrile (AIBN) was investigated kinetically in benzene. This polymerization proceeded heterogeously with formation of the very stable poly(NMMAm) radicals. The overall activation energy of this polymerization was calculated to be 23 kcal/mol. The polymerization rate (Rp) was expressed by: Rp = k[AIBN]0.63-0.68[NMMAm]1?2.5. Dependence of Rp on the monomer concentration increased with increasing NMMAm concentration. From an ESR study, cyanopropyl radicals escaping the solvent cage were found to be converted to the living propagating radicals of NMMAm in very high yields (ca. 90%). Formation mechanism of the living polymer radicals was discussed on the basis of kinetic, ESR spectroscopic, and electron microscopic results. 相似文献
Cobalt porphyrin complexes(TPPCoⅢX)(TPP = 5,10,15,20-tetraphenyl-porphyrin;X = halide) in combination with bis(triphenylphosphine) iminium chloride(PPNCl) were used for the copolymerization of cyclohexene oxide and CO2. The highest turnover frequency of 67.2 h-1 was achieved after 13 h at 20℃,and the obtained poly(1,2-cyclohexylene carbonate)(PCHC) showed number average molecular weight(Mn) of 10×103.Though the obtained PCHC showed atactic structure,the m-centered tetrads content reached 58.1%at CO2 pressure of 1.0 MPa,and decreased to 51.9%at CO2 pressure of 6.0 MPa,indicating that it was inclined to form atactic polymer at high CO2 pressure. 相似文献
The intent of the study is to attain a high selectivity rate and stable interaction between metals in any heterogeneous catalyst. Cyclohexene is extremely valuable in industrial domains such as the synthesis of perfumes and nylons, and the mesoporous alumina was upstretched with a various ratio of bimetal copper (10%) and nickel (5%, 10%, 15%, and 20%) under wet impregnation procedures by the mesoporous aluminum catalyst. This impregnation of a metal and catalyst was used to assess the highest conversion and selectivity of cyclohexene to cyclohexanol. This catalytic nature was validated by analyzing the crystal structure and size using the X-ray diffraction technique. The functional group is identified using FT-IR (Fourier Transform Infrared Spectroscopy), while the surface area is assessed using BET (Brunauer-Emmet-Teller). HR-TEM (transmission electron microscopy) is used to validate the morphology of catalysts and their surface layers; HR-SEM (Scanning Electron Microscopy) is used to highlight and assess microparticles; and NH3TPD (Temperature-Programmed Desorption) is used to measure the overall acidity of the catalyst. The catalytic performance was proved by the yield achieved by varying parameters such as temperature, pressure, WHSV−1, reaction time, and solvents, which yielded over 98.5% in both cyclohexene conversion and selectivity. In the conversion of the product, H2O2 performs as an oxidant, and acetonitrile serves as a solvent at constant mild conditions of 90 °C and 20 bar pressure. Furthermore, even after seven successive runs with the Al2O3/Cu (10%)-Ni (15%) mixture, remarkable reusability was attained despite a minor decline in cyclohexanol selectivity. The effective impregnation of copper and nickel into supported mesoporous Al2O3 produced a long-lasting, stable hybrid nanostructure with excellent stability and no metal leaching. The current synthesis protocol's advantages and qualities include its efficiency, cost-effectiveness, ecological sustainability, and comfort of synthesis with readily available components. 相似文献
Generation of high value polymers from carbon dioxide is of general technological interest given that CO2 is both inexpensive and relatively easy to handle on an industrial scale. Previous work on the use of CO2 as a comonomer has focused primarily on development of new catalysts, and the effects of conventional process variables such as temperature and concentration on the polymerization outcome have not been examined in great detail. Recently, we, as well as Darensbourg and colleagues, have shown that one can generate zinc-based catalysts for the polymerization of CO2 and cyclohexene oxide which produce over 400 grams of polymer per gram of metal. In this paper, we use a product of the reaction between zinc oxide and the fluorinated half-ester of maleic anhydride to generate copolymers of CO2 and cyclohexene oxide where CO2 is both reactant and sole solvent. In general, we found that the outcome of the polymerization depends greatly on the proximity to the ceiling temperature and the critical cyclohexene oxide concentration, and also on the phase behavior of the cyclohexene oxide-CO2 binary. 相似文献
A new amidoimidomalonate ligand was synthesized in a short and effective way and the zinc acetate complex thereof was prepared. XRD investigation revealed an unprecedented solid state structure, where the sedecameric complex [(lig)2Zn4(OAc)4]4 builds the edges of a square cavity. Each edge is made up by a similar unit [(lig)2Zn4(OAc)4] with four zinc atoms. The complex is an active catalyst in the copolymerization of CO2 and cyclohexene oxide and produces polyethercarbonates with broad molecular weight distributions. 相似文献
Thiophene was polymerized in high yield on exposure to aluminum chloride in solvent under mild conditions. Experimental evidence [IR, NMR, UV, and mass spectra, elemental analyses, reductive desulfurization, and comparison with the literature trimer of thiophene (prepared with phosphoric acid)] suggests the following structure: From gel permeation chromatography an average weight of 1290 was obtained, which corresponded to the presence of 15 rings; the highest-molecular-weight chains contained about 192 rings. Mechanistically, participation of cationic intermediates is proposed. Apparently chain extension can occur by various routes, including participation of neutral oligomer molecules. 相似文献