摘要:

2-Hydroxypropyl methacrylate (2-HPMA) has been copolym-erized with ethyl methacrylate (EMA), n-butyl methacrylate (BMA), and 2-ethylhexyl methacrylate (EHMA) in bulk at 60°C using benzoyl peroxide as initiator. The copolymer composition has been determined from the hydroxyl content. The reactivity ratios have been calculated by the Yezrielev, Brokhina, and Raskin method. For copolymerization of 2-HPMA (M1) with EMA (M2), the reactivity ratios are r1= 1.807 ± 0.032 and r2= 0.245 ± 0.021; with BMA (M2) they are n = 2.378 ± 0.001 and r2= 0.19 ± 0.01; and with EHMA the values are r1= 4.370 ± 0.048 and r2= 0.103 ± 0.006. Since reactivity ratios are the measure of distribution of monomer units in copolymer chain, the values obtained are compared and discussed. This enables us to choose a suitable copolymer for synthesizing thermoset acrylic polymers, which are obtained from cross-linking of hydroxy functional groups of HPMA units, for specific end-uses.

ISSN:0022-233X    

DOI:10.1080/00222338208063268

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Propylene was polymerized with the catalyst system (C2H5)2A1C1/ VCk/ anisole at -78°C using various conditions. The resulting polymers were successively extracted by diethyl ether, hexane, and heptane, leaving the residue. The polymers of the four series were characterized by intrinsic viscosity, gel permeation chromatography,13C nuclear magnetic resonance, infrared spectroscopy, x-ray diffraction, and by differential scanning calorimetry. The combined evidence from the various methods indicates that this catalyst system leads to stereoblock polymers which can be fractionated according to stereochemical composition and sequence length.

ISSN:0022-233X    

DOI:10.1080/00222338208063269

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Free radical photopolymerization of methyl methacrylate (MMA) in visible light was studied at 40°C using sulfur dioxide-halogen (Cl2, Br2, and I2) combinations as photoinitiators. Of the three SO2/halogen systems, only the SO2/Br2combination formed an interesting initiating system due to 1:1 complexation between the two components resulting in pronounced enhancement of the rate of photopolymerization over those produced by each of the initiator components when used as a lone photoinitiator. Photopolymerization ofMMAinduced by (SO2-Br2) complex (1:1) as the photoinitiator exhibited a low initiator exponent value, 0.26, and a monomer exponent value of 1.5. Kinetic nonidealities were explained on the basis of (a) monomer-dependent chain initiation and (b) significant initiator-dependent chain termination along with the usual bimolecular mode of chain termination.

ISSN:0022-233X    

DOI:10.1080/00222338208063270

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Cross-linked 4-vinylpyridine-styrene beads (PVPS) containing various amounts of pyridine rings were synthesized and reaction with methyliodide and peroxyacetic acid gave corresponding N-methylpyridinium salts and N-oxides with more than 92% of the pyridine rings being transformed. PVPS formed stable complexes with bromine and chlorine in the ratio 1:1, and when a higher amount of halogen was used, complexes with two molecules of halogen on each pyridine were formed. Similar complexes were also formed with PVPS-N-oxides in the presence of bromine and chlorine, while the reaction of PVPS-hydrohalide with bromine and chlorine resulted in hydrobromide perbromide and hydrochloride perchloride resins. The chemical activity of halo-substituted resins was tested in the reaction with 1,1-diphenylethylene. Chi or o-substituted resins are very stable, while bromo-substituted beads gave bromoalkene, dibromide, and alkoxybromide, depending on the structure of the reagent, solvent, and reaction temperature.

ISSN:0022-233X    

DOI:10.1080/00222338208063271

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

In order to study the effect of substituent groups of imidazole (Im) on the polymerization of methyl methacrylate (MMA) initiated with the system of Im compounds, copper(II) chloride, and water, polymerizations using N-ethylimidazole (N-Etlm) and 2-methylimidazole (2-MeIm) were carried out. The initiation ability for polymerization increased in the order 2-MeIm > N-Etlm > Im. The overall activation energies of polymerization initiated with N-Etlm and 2-MeIm were estimated to be 94.3 and 61.1 kJ/mol, respectively. The formation of complexes of the Cu(II) ion with substituted Im in water was confirmed by electronic spectra. Isolated complexes of [Cu(Im)4]Cl2, [Cu(2-MeIm)2]Cl2, [Cu(N-EtIm)2]Cl2, and [Cu(N-EtIm)4]Cl2, instead of free imidazoles, were used for the polymerization of MMA. These complexes, except [Cu(2-MeIm)2]Cl2, behaved as inhibitors of polymerization. This was due to the impossibility of formation of an adequate complex of MMA to initiate polymerization.

ISSN:0022-233X    

DOI:10.1080/00222338208063272

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The polymerization of methyl methacrylate (MMA) was carried out with a system of poly(N-vinylimidazole) (PNVIm), copper(n) chloride, and water at 85°C. The effects of the amount of each component on the conversion of MMA were investigated. The initiating ability of PNVIm was much larger than that of N-ethylimidazole; the macromolecular effect of the initiator was very remarkable. The polymerization proceeded through a radical mechanism. The overall activation energy was estimated to be 24.8 kJ/mol.

ISSN:0022-233X    

DOI:10.1080/00222338208063273

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Polymerization of acrylonitrile initiated by the Cr6+/thioacetamide redox system was studied in nitrogen atmosphere in the temperature range 35–45°C. The rate of polymerization and the rate of Cr6+ion disappearance were measured. The effect of certain water-miscible organic solvents, neutral electrolytes, and complexing agents on the rate of polymerization was investigated. Chromic acid alone did not initiate the polymerization under deaerated and undeaerated conditions. Depending on the results obtained, a suitable kinetic scheme was proposed and various rate parameters were evaluated.

ISSN:0022-233X    

DOI:10.1080/00222338208063274

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

For inorganic as well as for organic reactions the necessary raw materials in general are mixtures of different components. Different separation processes are needed before proceeding to the reactions resulting in the wished for transformation product. The development of new chemical procedures for obtaining energy or raw materials and their use without getting by-products or products without economical profit require new methods in chemical research.

ISSN:0022-233X    

DOI:10.1080/00222338208063275

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Graft copolymerizations of methyl methacrylate (MMA) on cellulose and oxycellulose were studied mostly under photo-activation with visible light using oxalic acid/KMnO4redox initiator in a limited aqueous system. Polymerization in the dark (40-60°C) produced little graft copolymer, while that in the light at 32° C produced significant or efficient grafting at reasonable rates. Cellulose, modified to degrees of oxidation corresponding to copper number 20–35, produced optimum grafting. Percent grating and grafting efficiency under different sets of conditions were studied and compared, and the mechanism of polymerization and graft copolymer formation discussed. Generation of grafting sites (radical centers) on cellulose/ oxycellulose was consequential only in the presence of light. Generally higher percent grafting and grafting efficiency in oxycellulose systems (as against cellulose systems) appear to be due to more easy and effective generation of radical sites on oxycellulose through oxidation of the aldehydic sites present in them in higher concentrations.

ISSN:0022-233X    

DOI:10.1080/00222338208063276

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

In order to examine the influence of the polarity of the reaction medium on the polyesterification mechanism, the kinetics of the reaction of 1-octadecanol with octadecanoic acid in octadecanyl octadecanoate is studied with and without p-toluenesulfonic acid catalyst. Without added catalyst the overall order is 2.5 and the orders in acid and in alcohol are 1.5 and 1, respectively. The mechanism consists of an autocatalysis by the acid and involves a nonnegligible dissociation of ion pairs. This differs from the observation made in more polar media. With added p-toluenesulfonic acid, the reaction is first order in alcohol, acid, and catalyst. Activation entropy is the same both for catalyzed and noncatalyzed reactions. The catalytic effect is due to a large decrease of activation enthalpy.

ISSN:0022-233X    

DOI:10.1080/00222338208063277

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor