共查询到20条相似文献,搜索用时 875 毫秒
1.
Chen Hou Chunnuan Ji Chunhua Wang Rongjun Qu 《Journal of polymer science. Part A, Polymer chemistry》2006,44(1):226-231
The reverse atom‐transfer radical polymerization (RATRP) technique using CuCl2/2,2′‐bipyridine (bipy) complex as a catalyst was applied to the living radical polymerization of acrylonitrile (AN). A hexasubstituted ethane thermal iniferter, diethyl 2,3‐dicyano‐2,3‐diphenylsuccinate (DCDPS), was firstly used as the initiator in this copper‐based RATRP initiation system. A CuCl2 to bipy ratio of 0.5 not only gives the best control of molecular weight and its distribution, but also provides rather rapid reaction rate. The rate of polymerization increases with increasing the polymerization temperature, and the apparent activation energy was calculated to be 57.4 kJ mol?1. Because the polymers obtained were end‐functionalized by chlorine atoms, they were used as macroinitiators to proceed the chain extension polymerization in the presence of CuCl/bipy catalyst system via a conventional ATRP process. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 226–231, 2006 相似文献
2.
Takumi Taninaka Takeshi Ogawa Yuji Minoura 《Journal of polymer science. Part A, Polymer chemistry》1975,13(10):2353-2362
It was found that acrylonitrile was polymerized at 30°C by ultraviolet irradiation in the presence of triphenyl phosphite and its derivatives, namely m-CH3, p-C2H5, and p-CH3 substituted triphenyl phosphites under conditions where acrylonitrile alone did not polymerize and phosphites did not undergo photolysis. The rate of polymerization in the presence of triphenyl phosphite and tri-p-tolyl phosphite was found to be proportional to the monomer concentration, the phosphite concentration, and the light intensity. From these results, it was thought that a donor–acceptor complex formed between phosphite and acrylonitrile which absorbed light and initiated the radical polymerization. In the photopolymerization of acrylonitrile with substituted triphenyl phosphites, the rate of polymerization increased with an increase in electron-donating ability of substituent. From the plot obtained by use of Hammett's equation (log Rp/Rp0 = ρσ), the ρ value was found to be ?1.0. 相似文献
3.
R. K. Samal G. V. Suryanarayana D. P. Das S. Samal M. C. Nayak 《Journal of polymer science. Part A, Polymer chemistry》1981,19(2):487-493
The aqueous polymerization of acrylonitrile initiated by the bromate—ferrous redox system in aqueous sulfuric acid was studied under nitrogen atmosphere. The rate of polymerization increased with increasing concentration of ferrous in the range of 0.25-1 × 10?2M. The percentage of conversion increased with increasing concentration of the catalyst, but beyond 2.5 × 10?3M there was a decreasing trend in the rate of polymerization. The rate varied linearly with [monomer]. The initial rate of polymerization as well as the maximum conversion increased within the range of 1–2.5 × 10?3M KBrO3, but beyond 2.5 × 10?3M the rate of polymerization decreased. The initial rate and limiting conversion increased with increasing polymerization temperature in the range 30–40°C; beyond 40°C they decreased. The effect of certain neutral salts, water-miscible solvents, complexing agents, and copper sulfate concentration on the rate of polymerization was investigated. 相似文献
4.
Radiation-induced polymerization of acrylonitrile (AN) in the ZnCl2-AN-H2O ternary system was carried out at temperatures ranging from 30 to ?78°C, and correlation between the polymerization rate and the concentration of complexed AN with zinc atom was clarified. The selected systems were in the supercooled liquid state at ?78CC with the molar composition ratio of ZnC12:AN:H2O of 1:1:3. The polymerization is free-radical in character. The 0.5-power dependence of the polymerization rate on the dose rate at 30°C indicates bimolecular termination, while the 0.9-power dependence at ?78°C shows predominant unimolecular termination because of the high viscosity of the systems at Just above the glass transition temperature. The negative temperature dependence of the polymerization rate is indicative of the tendency of the complex concentration to increase with lower temperatures. The polymerization rate, therefore, is proportional to the 2 and 1.5 powers of the complex concentration at ?78 and 30°C, respectively. These results indicate participation of the complexed monomer both in generation of the initiating radical species on irradiation and in the propagation step. A kinetic scheme has been proposed on the basis of the results. 相似文献
5.
Ignc Capek Jaroslav Barton 《Journal of polymer science. Part A, Polymer chemistry》1979,17(4):937-942
Polymerization of acrylonitrile photoinitiated by naphthalene, anthracene, phenanthrene, and pyrene is accelerated by an admixture of zinc (II) chloride, acetate, or nitrate. The effect of zinc (II) salts on the rate of pyrene-photoinitiated polymerization of acrylonitrile leads to an increase in this rate in the order Zn/OCOCH3/2 < ZnCl2 < Zn/NO3/2. The maximum polymerization rate is achieved at the molar ratio [ZnCl2]/([ZnCl2] + [pyrene]) approximately 0.7. In contrast to the photoinitiated polymerization of acrylonitrile, the methyl methacrylate admixture of zinc (II) chloride exerts a smaller effect on the polymerization rate. In the pyrene-photoinitiated polymerization of styrene an admixture of zinc (II) chloride retards the polymerization rate. Fluorescence of aromatic hydrocarbon in the system acrylonitrile–aromatic hydrocarbon is efficiently quenched by zinc (II) chloride. Stern–Volmer constants determined for pyrene (80 dm3 mole?1), phenanthrene (66 dm3 mole?1), and naphthalene (49 dm3 mole?1) are higher by about 2–3 orders of the Stern–Volmer constants for fluorescence quenching of aromatic hydrocarbons by acrylonitrile in the absence of ZnCl2. The fluorescence of anthracene in acrylonitrile is not quenched by ZnCl2. The acceleration effect of Zn (II) salts on the polymerization of acrylonitrile photoinitiated by aromatic hydrocarbons depends on two factors: an increase in the ratio of the rate constant of the growth and termination reactions, kp/kt, and an increase in the quenching constant of fluorescence of aromatic hydrocarbon, kq, by the complex {acrylonitrile…ZnCl2}. ZnCl2 thus influences both the growth and initiation reactions of the polymerization process. 相似文献
6.
Arun K. Roy Samuel Pattnaik Rajani K. Samal Padma L. Nayak 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(8):1241-1249
The polymerization of acrylonitrile initiated by the redox system K2S2O8-citric acid catalyzed by Ag+ ion has been studied over the temperature range 35–50°C. The rate of polymerization is proportional to the square root of peroxydisulfate concentration. The initial rate increases with increasing citric acid concentration, but at relatively higher concentration of citric acid the rate decreases. The rate of polymerization also increases with increasing monomer concentration and temperature. The overall activation energy calculated from the Arrhenius plot was found to be 4.6 kcal/mole. On the basis of the observation, a suitable kinetic scheme has been proposed for the reaction. 相似文献
7.
Jaroslav Barto Ignc Capek Pavol Hrdlovi
《Journal of polymer science. Part A, Polymer chemistry》1975,13(12):2671-2690
The kinetics of acrylonitrile polymerization photoinitiated by aromatic hydrocarbons have been studied. For the acrylonitrile polymerization photoinitiated by naphthalene the rate of polymerization depends on the square root of incident light intensity, on the square root of naphthalene concentration, and on the 1.5 power of acrylonitrile concentration. In the system acrylonitrile-1-methoxynaphthalene the rate of acrylonitrile polymerization depends on the first power of acrylonitrile concentration. The monoradical character of this polymerization process has been established. For the interpretation of experimental results a reaction mechanism involving the formation of the exciplex between the first singlet or triplet of aromatic hydrocarbon and acrylonitrile in the ground state as a precursor of polymerization reactions is suggested. The photoinitiating efficiency of various aromatic hydrocarbons in acrylonitrile polymerization increases in the order: fluoranthene (zero efficiency) ? pyrene < phenanthrene, fluorene ≈ 2-methoxynaphthalene ≈ biphenyl < anthracene < 2-methylnaphthalene < 1-methoxynaphthalene < 2,3,6-trimethylnaphthalene < 2,3-dimethylnaphthalene ≈ naphthalene < 1-methylnaphthalene < 2,6-dimethylnaphthalene < p-terphenyl < acenaphthene, provided that the systems absorb the same amount of the incident light. The explanation of this result ensues from the study of the effect of concentration on the rate of polymerization and from the quenching of hydrocarbon fluorescence by acrylonitrile. The photoinitiating efficiency of a given aromatic hydrocarbon is mainly determined by the value of the rate constant kq for the formation of exciplex as well as the self-quenching efficiency of aromatic hydrocarbon. By using the literature data for the lifetime of fluorescence τ the values of kq were calculated from the Stern-Volmer equation expressing the quenching of hydrocarbon fluorescence by acrylonitrile. The order of aromatic hydrocarbons according to increasing values of kq is as follows: pyrene < phenanthrene < anthracene ≈ naphthalene < 2-methylnaphthalene ≈ 1-methylnaphthalene ≈ 2,3-dimethylnaphthalene < 2,6-dimethylnaphthalene < acenaphthene < p-terphenyl < 1-methoxynaphthalene. The study of the concentration effect reflecting the self-quenching of aromatic hydrocarbons during polymerization has given the following sequence for decreasing self-quenching efficiency of aromatic hydrocarbons: 2-methoxynaphthalene ≈ pyrene > anthracene > 1-methoxynaphthalene > fluorene > 2,6-dimethylnaphthalene, phenanthrene, acenaphthene > 2,3,6-trimethylnaphthalene > 2,3-dimethylnaphthalene > 1-methylnaphthalene > naphthalene. It has been shown that the photoinitiating efficiency of a given aromatic hydrocarbon in the polymerization of acrylonitrile can be roughly predicted from the position of that aromatic hydrocarbon in the above-mentioned sequences. 相似文献
8.
Reverse atom transfer radical polymerization (RATRP) of acrylonitrile (AN) was carried out using azobisisobutyronitrile (AIBN) as initiator, ferric trichloride anhydrous (FeCl3)/lactic acid (LA) as catalyst system; a ratio of FeCl3/LA was 1:2 gave the best control. RATRP of AN with N,N-dimethylformamide (DMF) as solvent gave the moderate polymerization rate and the narrowest polydispersity index (PDI). When FeCl3 was replaced by CuBr2, RATRP of AN showed a longer induction period. When Cu was added to the CuBr2-based catalyst system, the induction period was reduced. 1H-NMR spectra of PAN verified the possibility of controlled/living polymerization for future chain extension. 相似文献
9.
Takumi Taninaka Takeshi Ogawa Yuji Minoura 《Journal of polymer science. Part A, Polymer chemistry》1975,13(11):2591-2604
The radical polymerization of acrylonitrile in the presence of nuclear-substituted triphenyl phosphites (p-Cl, H, p-CH3, p-OCH3) initiated by α,α′-azobisisobutyronitrile at 50°C was investigated. It was found that the rate of polymerization decreased at low concentrations of phosphite, but after reaching a minimum the rate increased again with further increase in the phosphite concentration in the case of all substituted triphenyl phosphites. Formation of a weak complex between phosphite as donor and acrylonitrile as acceptor was confirmed from the change in chemical shifts of vinyl protons to higher magnetic fields on NMR spectroscopy. From the results of continuous variation method using NMR spectra, the complex was found to be of the 1:1 type. The effects of substituted triphenyl phosphite on the rate of polymerization and the chain-transfer reaction to substituted triphenyl phosphites are discussed on the basis of these results. 相似文献
10.
The cationic alkyl zirconocene complex Cp2Zr+Me[CH3B−(C6F5)3] is found to initiate the ringopening polymerization of 1,5,7,11-tetraoxaspiro[5,5]undecane under mild condition to give poly(oxypropylenepropylenecarbonate) with low polydispersity. The rate of the polymerization is first-order with respect to monomer and catalyst concentration. At high monomer concentration, the initial rate of polymerization becomes zero-order with respect to monomer concentration. 相似文献
11.
Yang Kyoo Han Moon Young Jin Sam Kwon Choi 《Journal of polymer science. Part A, Polymer chemistry》1983,21(1):73-81
Polymerization of acrylonitrile initiated by a potassium superoxide (KO2)-nitrobenzene system was carried out in anhydrous dimethylsulfoxide (DMSO) at 25°C. The initial rate of polymerization was rapid and a high-molecular-weight polymer was obtained. The molecular weight was proportional to monomer concentration and inversely to concentration of initiator within 5 min. The overall activation energy was estimated as ?2.6kcal/mol deg in the temperature range of 20–50°C. In addition to nitrobenzene anion radical, other anion radicals generated by one-electron transfer from KO2 to charge transfer agents such as m-dinitrobenzene benzoquinone, benzophenone, and naphthalene were effective in the polymerization of acrylonitrile. It is proposed that polymerization proceeds via an anionic mechanism that involves one-electron transfer from anion radicals to monomer. 相似文献
12.
V. G. Gandhi A. B. Deshpande S. L. Kapur 《Journal of polymer science. Part A, Polymer chemistry》1974,12(6):1173-1179
Methyl methacrylate was polymerized at 40°C with VOCl3–AlEt2Cl catalyst system in n-hexane. The rate of polymerization was proportional to catalyst and monomer concentration at Al/V ratio of 2 and overall activation energy of 9.25 kcal/mole support a coordinate anionic mechanism of polymerization. The catalytic activity and stereospecificity of this catalyst system is discussed in comparison with that of VOCl3–AlEt3 catalyst system. 相似文献
13.
Chen Hou Rongjun Qu Chunnuan Ji Chunhua Wang Chengguo Wang 《Journal of polymer science. Part A, Polymer chemistry》2006,44(1):219-225
FeCl3 coordinated by isophthalic acid was first used as a catalyst in the azobisisobutyronitrile‐initiated reverse atom transfer radical polymerization of acrylonitrile. N,N‐Dimethylformamide was used as a solvent to improve the solubility of the ligand. An FeCl3‐to‐isophthalic acid ratio of 0.5 not only gave the best control of the molecular weight and its distribution but also provided rather a rapid reaction rate. The effects of different solvents on the polymerization of acrylonitrile were also investigated. The rate of the polymerization in N,N‐dimethylformamide was faster than that in propylene carbonate and toluene. The molecular weight of polyacrylonitrile agreed reasonably well with the theoretical molecular weight in N,N‐dimethylformamide. The rate of polymerization increased with increasing polymerization temperature, and the apparent activation energy was calculated to be 59.9 kJ mol?1. Reverse atom transfer radical polymerization was first used to successfully synthesize acrylonitrile polymers with a molecular weight higher than 80,000 and a narrow polydispersity as low as 1.22. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 219–225, 2006 相似文献
14.
This article reports the polymerization kinetics of acrylonitrile initiated by metallic magnesiumnitric acid system. The rate of polymerization is independent of the amount of magnesium used; when the concentration of nitric acid is higher than acrylonitrile, the equation of polymerization kinetics may be expressed asR_p =1.91×10~5e~(-15000)/RT[Mg]~0 [AN]~(2.2) [HNO_3]~(0.45)The result of copolymerization of acyrlonitrile and methyl acrylate supports a free-radical mechanism. 相似文献
15.
S. L. Malhotra A. B. Deshpande S. L. Kapur 《Journal of polymer science. Part A, Polymer chemistry》1968,6(1):193-203
The polymerization of styrene with two catalyst systems consisting of Al(C2H5)3 in combination with ZrCl4 or ZrCl3 has been studied. The rate of polymerization with catalyst concentration was first-order with ZrCl4 system and second-order with ZrCl3 system, but at higher catalyst concentrations in both cases, the rate progressively decreases and finally attains a low value. The rate of polymerization is, however, proportional to the square of the monomer concentration in both the cases. The overall energy of activation was 10.9 kcal./mole and 6.45 kcal./mole in these systems. The polymers obtained with ZrCl4 were of lower molecular weights as compared to those obtained with ZrCl3. The polymers in both the cases had amorphous character. 相似文献
16.
The radiation-induced polymerization of acrylonitrlle in frozen aqueous zinc chloride solution was carried out at low temperatures. A marked enhancement both in the rate and the degree of polymerization was observed at zinc chloride/acrylonitrile molar ratios above unity, which indicated the importance of formation and stabilization of complexes in the frozen medium. The rate of polymerization R was found to follow the relation, R α [M-ZnCl2]2 I, where I is the dose rate and [M-ZnCl2] is the concentration of zinc chloride complexed with equimolecu-lar monomer. It is considered that the role of zinc chloride is here dual, both as a reagent for complex formation and also as a source of initiating species on irradiation. The effect of coexisting saturated nitriles were also discussed. 相似文献
17.
Y. N. Sharma V. G. Gandhi I. S. Bhardwaj 《Journal of polymer science. Part A, Polymer chemistry》1980,18(1):59-64
Vinyl acetate and acrylonitrile were copolymerized with Co(acac)3-Al(C2H5)3 catalyst system in benzene at 40°C. The rate of copolymerization is linearly proportional to monomer concentration and catalyst concentrations up to a certain value. The overall activation energy was found to be 11.3 kcal/mole. The effect of hydroquinone on the rate of copolymerization indicates the presence of free radicals in this system. The possibility of simultaneous formation of coordinate anionic and free radical active sites has been proposed. 相似文献
18.
Subasini Lenka Akshaya K. Dhal 《Journal of polymer science. Part A, Polymer chemistry》1982,20(3):587-591
The polymerization of acrylonitrile was carried out using peroxydiphosphate-cyclohexanol redox system in the presence of silver ion. The rate of polymerization increases with increasing peroxydiphosphate concentration and the initiator exponent was computed to be 0.5. The rate of polymerization increases with increasing monomer concentration and the monomer exponent was computed to be unity. The plot of Rp vs [Ag+]1/2 was linear, indicating 0.5 order with respect to [Ag+]. The reaction was carried out at three different temperatures and the overall activation energy was calculated to be 7.60 kcal/mol. The effect of certain surfactants on the rate of polymerization has been investigated and a suitable kinetic scheme has been pictured. 相似文献
19.
The kinetics of polymerization of acrylonitrile (AN) initiated by quinquevalent vanadium (V~(5+))-thiourea (TU) redox system has been investigated in aqueous nitric acid in the temperature range from 30 to 50℃. The polymerization rate (R_p) can be expressed as follows: In the copolymerization of acryionitrile with methyl acrylate (MA), the reactivity ratios were found to be 1.0 and 1.1, respectively. The experimental observations suggest that the initiating species is probably a complex consisting of a central ion of Lewis acid-VO_2~+ and the ligands of Lewis bases-acrylonitrile, thiourea, and nitrate anions, while the initiating system in lower concentration, the polymerization of acrylonitrile does not occur if the thiourea is acidified prior to its reaction with quinquevalent vanadium. This indicates that the primary radicals (or the monomeric radicals in the present article) are produced by associated thiourea rather than isothlourea. 相似文献
20.
A. B. Deshpande S. M. Kale S. L. Kapur 《Journal of polymer science. Part A, Polymer chemistry》1972,10(1):195-203
A homogeneous catalyst system, Cr(C5H7O2)3–Al(C2H5)3, was used for the polymerization of methyl methacrylate. The yield of polymer increased up to an Al/Cr ratio of 12 and thereafter remained almost constant with increasing Al/Cr. The rate of polymerization increased linearly with increasing catalyst and monomer concentrations at Al/Cr = 12. The molecular weight, however, decreased with increasing catalyst concentration and increased with increasing monomer concentration, indicating anionic polymerization reaction. NMR studies of the polymers indicated the presence of a stereoblock structure, which changed to heteroblock structure in presence of triethylamine and hydroquinone as additives in the catalyst. In the light of these observations, the mechanism of the polymerization is discussed. 相似文献