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1.
The polymerization of vinyl monomer initiated by poly-p-vinylphenol (PVPh) in NaOH aqueous solution was carried out at 85°C with shaking. Methyl methacrylate (MMA) was polymerized, whereas styrene and acrylonitrile were not. PVPh, which is dissociated into phenolate form (PVPh?Na+) in NaOH aqueous solution, was effective for the polymerization. The effects of the amounts of MMA, PVPh, NaOH, and H2O on the conversion of MMA were studied. The rate of polymerization of MMA increased with an increase in the molecular weight of PVPh-Na. The overall activation energy was estimated as 54 kJ mol?1. The polymerization proceeded through a radical mechanism. The addition of tetra-n-butylammonium bromide increased the rate of polymerization.  相似文献   

2.
Aqueous polymerization of methyl methacrylate (MMA), initiated by the potassium bromate-thioglycollic acid (TGA) redox system, has been studied at 30 ± 0.2° C under positive pressure of nitrogen. The rate is given by K[MMA] [TGA] 0[KBrO3]x where × = 1 for lower KBrO3 concentrations and 0.5 for higher KBrO3 concentrations. The reaction has been studied over the 20–45°C range. The activation energy was found to be 65.72 kJ/mol (15.71 kcal/mol) in the investigated range of temperature. Inorganic electrolytes except MnSO4·4H2O and Na2C2O4 depress both the rate of polymerization and the maximum conversion. All the alcohols (viz., MeOH, EtOH, iso-PrOH, tert-BuOH) and acetone depress the rate of polymerization as well as the maximum conversion.  相似文献   

3.
Binary systems consisting of dimethylaniline-N-oxide (DMOA) and some α-halo-carbonyl compounds, such as phenacyl halide and α-halo-acetic acid ester, were found to induce radical polymerization of vinyl monomers. Bromo-derivatives showed higher initiating activities than chloroderivatives. The polymerization of methyl methacrylate (MMA) with DMAO and phenacyl bromide (PBr) was investigated kinetically. The polymerization rate (Rp) was expressed as follows; Rp = k[DMAO]12[PBr]12[MMA].The overall activation energy of the polymerization was calculated to be 42.7 kJ mol?1. No noticeable chain-transfer from the polymer radical to DMAO or PBr was observed. The benzoyl radical was trapped by 2-nitroso-2-methylpropane, a spin trapping reagent, in the reaction of DMAO and PBr. The u.v. spectrum of poly (MMA) obtained suggests that the polymer contains end-groups similar to acetophenone and DMA. From the results, an initiation mechanism for the polymerization has been proposed and discussed.  相似文献   

4.
The charge-transfer complex formed between an amine and carbon tetrachloride can initiate the polymerization of vinyl monomers in a nonaqueous solvent such as dimethylsulfoxide. Here we use cyclopentylamine (CPA) and heptylamine (HA) as the donor compounds for charge-transfer initiation of the polymerization of methl methacrylate (MMA). The rate of polymerization Rp = k[MMA]1 [amine]0.5 [CCl4]0.5 when [CCl4] [amine] ≤ 1; when [CCl4] [amine] < 1, Rp becomes independent of [CCl4] and Rp = k[MMA]1.5 [amine]0.5. The average constant at 60°C for the polymerization of MMA in terms of monomer were (1.66 ± 0.03) × 10?5 and (1.46 ± 0.04) × 10?5 s?1 with CPA and HA, respectively, when [CCl4] [amine] ≤ 1, and (1.16 ± 0.04) × 10?5 and (1.39 ± 0.08) × 10?1 L/mol·s when [CCl4]/[amine] < 1.  相似文献   

5.
Using p,p'-dimethoxydiphenyldiazomethane (DMDM) as initiator, the polymerization of methyl methacrylate (MMA) in benzene or in bulk was carried out. The initial rate of polymerization, Rp, was found to be expressed by the following equation:

Rp = k[DMDM]0.53 [MMA]0.84

The polymerization was confirmed to proceed by a radical mechanism. The over-all activation energy for the polymerization in benzene was calculated as 19.3 kcal/mole. The rate of thermal decomposition of DMDM was also measured in benzene and the rate equation was obtained as follows:

kd (sec?1) = 1.0 × 1015 exp (?29.1 kcal/RT) (for 50-80°C)

Explanations of these observations are discussed in connection with those of the preceding papers.  相似文献   

6.
The redox-initiated polymerization of methyl methacrylate (MMA) by the Ce(IV)-malic acid system has been carried out in aqueous medium under an inert atmosphere. The rate of polymerization was found to be proportional to [MMA]3/2 [MA]1/2 [Ce(IV)]1/2 and the rate of ceric ion disappearance was proportional to [Ce(IV)] but independent of [MMA]. The rate increased linearly up to a certain range of [MA], above which it remained constant. Increasing [H2SO4] decreased the rate. The activation energy was found to be 57.44 kJ/mol.  相似文献   

7.
Some electron-accepting compounds such as maleimide (MIm), maleic anhydride (MAn), and tetracyanoquinodimethane were found to show pronounced accelerating effects on vinyl polymerization initiated with metal chelates. The polymerization of methyl methacrylate (MMA) initiated with bis(ethyl acetoacetato)-copper(II) (Cu(eacac)2) and MIm was studied kinetically in benzene. The overall activation energy of the polymerization was calculated to be 11.5 kcal/mol. This value was much lower than that (17.6 kcal/mol) for the polymerization of MMA with Cu(eacac)2 alone. The polymerization rate (Rp) was expressed as Rp =k[MIm]1/2 [Cu(eacac)2]1/2 [MMA] The first-order dependence of Rp on the monomer concentration indicated that the monomer had no participation in the initiation step, in contrast with polymerization in the absence of MIm (where a monomer concentration dependence of 1.4th order was observed). Electronic spectroscopic study revealed that a complex between MIm and Cu(eacac)2 had been formed. The ligand radical, an acetylcarboethoxymethyl radical, was trapped by 2-methyl-2-nitrosopropane in the reactions of Cu(eacac)2 with MIm and with MAn in benzene. From these results the mechanism of the initiation of polymerization is discussed.  相似文献   

8.
The polymerization of methyl methacrylate (MMA) initiated with a system of oxycellulose, CuCl2, and water was carried out. The conversion of MMA and the degree of polymerization of homopoly-MMA were larger than obtained with the initiator system of cellulose, CuCl2 and water, while the efficiency of grafting was almost the same. It was confirmed that the polymerization proceeds through a radical mechanism. The effects of amounts of cupric chloride, water, and MMA in the feed on the conversion were studied. The pH of the water phase showed a remarkable effect: maximum conversion was obtained at neutral pH. At 90°C, a ceiling temperature was observed. The overall activation energy was estimated to be 96.7 kJ/mole. The initiation mechanism is discussed.  相似文献   

9.
Polymerization of methylmethacrylate (MMA) with aminoalcohols, namely ethanolamine (EA), diethanolamine (DEA) and triethanolamine (TEA) in the presence of carbontetrachloride (CCl4) has been investigated in the dimethylsulfoxide (DMSO) medium by employing a dilatometric technique. The rate of polymerization (R p) has been evaluated under the conditions and > 1. The kinetic data reveal the possible participation of a charge-transfer complex in the polymerization reaction. In the absence of either CCl4 or amine, no polymerization of MMA was observed under the present experimental conditions. The polymerization of MMA was inhibited by hydroquinone, indicating a free radical initiation.  相似文献   

10.
The kinetics of the polymerization of methyl methacrylate (MMA) in the presence of imidazole (Im), 2-methylimidazole (2MIm), or benz-imidazole (BIm) in tetrahydrofuran (THF) at 15–40°C was investigated by dilatometry. The rate of polymerization, Rp , was expressed by Rp = k[Im] [MMA]2, where k = 3.0 × 10?6 L2/(mol2 s) in THF at 30°C. The overall activation energy, Ea , was 6.9 kcal/mol for the Im system and 7.3 kcal/mol for the 2MIm system. The relation between logRp and 1 T was not linear for the BIm system. The polymers obtained were soluble in acetone, chloroform, benzene, and THF. The melting points of the polymers were in the range of 258–280°C. The 1H-NMR spectra indicated that the polymers were made up of about 58–72% of syndiotactic structure. The polymerization mechanism is discussed on the basis of these results.  相似文献   

11.
Effects of pentavalent phosphorus compounds on the radical polymerization of methyl methacrylate (MMA) and styrene (St) were studied. Phosphorus oxychloride (Cl3P?O) and phenyl-phosphonic dichloride (C6H5Cl2P?O) were used. Polymerization was carried out in benzene at 50°C by the standard solution method, α,α′-azobisisobutyronitrile (AIBN) being used as the initiator. In the polymerization of MMA, both phosphorus compounds increased the rate of polymerization. NMR spectral data suggested that this increasing effect was due to the complex formation between each phosphorus compound and MMA monomer. In the case of polymerization of St, NMR data also indicated the formation of a complex between the phosphorus compound and St monomer. Both phosphorus compounds showed an increasing effect for the rate of polymerization. Though these increasing effects could be explained by the complex formation, the polymerization of St in the presence of Cl3P?O was especially found to be due to the cationic polymerization initiated simultaneously by Cl3P?O in addition to the radical polymerization. These phosphorus compounds acted as chain-transfer agents in both polymerization systems. The parameters (Qtr,etr) which indicate the reactivity of a chain-transfer agent were calculated from the observed values of chain-transfer constant for both polymerization systems.  相似文献   

12.
The radical polymerization of methyl methacrylate (MMA) was carried out with the system of imidazole (Im), copper(n) chloride, and water at 85°C. The effects of the amount of each component on the conversion of MMA were investigated. The polymerization proceeded through a radical mechanism. The overall activation energy was estimated to be 28.7 kJ/mole. The conversion of MMA showed a maximum at pH 8-9 of the aqueous solution. The formation of a complex of CuCl2 with Im, water, and MMA was confirmed by electronic spectra. An initiation mechanism was proposed.  相似文献   

13.
Diphenylsulfone (DPSO2) was found to react with an equimolar amount of potassium in tetrahydrofuran (THF), dimethoxyethane (DME), or diglyme (DG) at reflux or an elevated temperature to yield a reddish-black solution, giving an electron spin resonance (ESR) signal. The signal was attributed to the formation of relatively labile DPSO2 anion radical. The apparent effects of solvents on the reactivity of DPSO2 with potassium depended on the polarities and the solvation powers: benzene ? toluene ? dioxane ? tetrahydrofuran < monoglyme < diglyme. The monopotassium complex was found to react further with another molecular amount of the metal to yield a dark blue solution giving no ESR signal. The monopotassium complex initiated the polymerization of acrylonitrile (AN). It did not, however, initiate the polymerization of methyl methacrylate (MMA), styrene (St), or isoprene (IP). The active species of the monopotassium complex that initiated the polymerization of AN was found from analyses of the reaction products and the infrared spectrum of oily oligomer of AN obtained by the complex to be potassium benzenesulfinate. The dipotassium complex was found to initiate the polymerization of MMA, St, IP and AN. The active species of the dipotassium complex that initiated the polymerization of MMA, St, or IP was found from analyses of the reaction products and the infrared spectrum of the oily oligomer of MMA obtained by the complex to be phenyl potassium.  相似文献   

14.
Benzaldehyde (PhCHO) is found to be able to initiate the radical polymerization of methyl methacrylate (MMA). The rate of polymerization is expressed by the following equation: Rp = const[PhCHO]0.5[MMA]1.5. The overall activation energy is estimated to be 56.3 kJ mole?1. The mechanism of polymerization is discussed.  相似文献   

15.
Methyl methacrylate (MMA) can be polymerized by a charge transfer complex formed by the interaction of urea, methyl methacrylate, and carbon tetrachloride (CCl4) in a nonaqueous solvent like dimethylsulfoxide (DMSO). The rate of polymerization can be accelerated by Lewis acids like Fe3+. This article reports the polymerization of MMA initiated by urea and CCl4 and accelerated with hexakisdimethylsulfoxide iron (III) perchlorate, [Fe(DMSO)6](ClO4)3, and A at 60°C. Definite induction periods were observed for the polymerization reaction initiated by urea and CCl4 alone, but the induction period completely vanished when the molar ratio of urea to A reached 6:1. The molecular weights of the polymers with 6:1 molar ratio of urea to A were higher than with urea alone. The rate constant for the polymerization of MMA in the presence of [Fe(urea)6]3+ was 1.03 × 10?5 1 mol?1 s?1 at 60°C. The transfer constant for CCl4 for polymerization with urea alone is 2.43 × 10?3 at 60°C.  相似文献   

16.
In the anionic polymerization of methyl methacrylate (MMA) induced by imidazole (Im), an Im‐MMA adduct forms as an initiator adduct in methanol at 30°C in an argon atmosphere by the equimolar reaction of Im with the MMA monomer. The additive effect of the adduct on the homopolymerization of MMA in tetrahydrofuran at 30°C was investigated by dilatometry. The existence of the adduct increased the duration of the propagation step without shortening the formation step of the initiator adduct. The H‐D exchange reaction of the adduct was observed in D2O by 1H NMR. Proton transfer of the MMA unit in the adduct was not observable until 45 h after initiation. The copolymerizability of MMA with acrylamide (AAm) induced by the Im catalyst in THF at 30°C was also investigated. It was found that the homo‐and copolymerizations proceeded at the same time. On the other hand, in the MMA homopolymerization system, the addition of AAm monomer during the initial propagation step yielded copolymer of MMA and AAm for near equimolar concentration of the charged monomers.  相似文献   

17.
The polymerization of vinyl monomers initiated with the system of polyvinylferrocene (PVFc) and carbon tetrachloride (CCl4) was carried out in dark. Methyl methacrylate (MMA) and acrylonitrile (AN) could be polymerized, while styrene (St) was hardly polymerized under the conditions used. The polymerization proceeded through a free-radical mechanism and was concluded to be initiated by attack of vinyl monomer, having a polarized vinyl group, on the charge-transfer complex of PVFc/CCl4. In the polymerization of MMA, the initiating ability of PVFc was much larger than that of ferrocene (Fc-H) or poly(ferrocenylmethyl methacrylate) (PFMMA) and was comparable to that of polyferrocenylenemethylene (PFM). The overall activation energy was estimated to be 34.2 kJ/mole.  相似文献   

18.
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   

19.
Radiation-induced polymerization of methyl methacrylate (MMA) was studied up to 7500 kg/cm2 at 20°C. The rate of polymerization increased to 3000 kg/cm2 with overall activation volume ΔVpol? of -23.6 cm3/mole, and then the pressure dependence of the rate was very small in the pressure range between 3000 and 3700 kg/cm2. The rate of polymerization increased again above 3700 kg/cm2 up to the crystallization pressure of MMA (5500 kg/cm2) with ΔVpol? of -13.7 cm3/ mole with increasing pressure. The volume contraction by polymerization decreased with increasing pressure up to 3000 kg/cm2 but hardly decreased with increasing pressure above 3000 kg/cm2. The stereoregulzarity (triad probability) of PMMA changed slightly at 3000 kg/cm; above 3000 kg/cm2, syndiotactic addition decreased and heterotactic addition increased. Marked change in P-V isotherms of MMA, however, was not observed about 3000 kg/cm2. We concluded from these facts that an alignment of monomer molecules, which does not cause large volume change, was realized about 3000 kg/cm2. Polymerization proceeded above the crystallization pressure by long time irradiation, and isotactic addition increased clearly in the solid-state polymerization.  相似文献   

20.
Emulsion polymerization of tetrafluoroethylene and propylene with ammonium perfluorooctanoate, initiated by a redox system containing tert-butylperbenzoate (TBPB) was carried out. The effect of the components of the redox system Is (TBPB, FeSO4.7H2O, ethylenediamine tetraacetic acid (EDTA), and CH2(OH)SO2Na.2H2O) on the polymerization rate (R) and molecular weight () was studied. Among redox system components, Fe2+ concentration exerts the most significant effect (by power of 0.54) on the polymerization rate. It was found that R ∝ [Is]0.2–0.54 and Mn ∝ [Is]0.0–0.1 and polymerization reaction scheme was suggested for the action of the initiating system. The influence of the copolymerization conditions (pressure, temperature, stirring speed, and pH) is also discussed. The apparent activation energy of the reaction was found to be 46.0 kJ/mol. © 1994 John Wiley & Sons, Inc.  相似文献   

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