摘要:

No other area of polymerization has been the subject of as many studies, especially of mechanism, as that of emulsion polymerization and copolymerization [1, 21. This fact arises not only from what has been regarded as the distinctive features of emulsion polymerization as a process but also from the highly diverse character of emulsion polymerization arising from the specific nature of the monomers utilized and the polymers produced and their influence on the course of the process itself.

ISSN:0022-233X    

DOI:10.1080/00222338208056476

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The intense yellow colored complexes of Ti(IV) and N-pyridy1-N′-β-naphthylthiourea are extractable into isoamyl alcohol. The spectrophotometric studies following Job's and molar ratio methods have shown that 1:2 and 1:3 (meta1:ligand) complexes predominate in the acidity ranges of 2.5–6 and 7–9.5NHCl, respectively. The values of the stability constants, sepwise and overall, have been calculated following extended Leden's, Yatsimirskii's, and Harvey-Manning's methods. The analytical suitability of the reagent for microdetermination of titanium has also been investigated.

ISSN:0022-233X    

DOI:10.1080/00222338208056477

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The copolymerization of castor oil prepolymer (COP) was attempted with vinyl monomers in the presence of a free radical initiator at 75°C. It was found that acrylonitrile copolymerizes with COP in good yield, The copolymers were yellow brown in color and were soluble in hot dimethylformamide. The percentage composition of the copolymers was determined by the nitrogen of the copolymers. Their reactivity ratios were determined to be r1= 0.53, r2= 1.53.

ISSN:0022-233X    

DOI:10.1080/00222338208056478

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The graft copolymerization of methyl methacrylate onto silk fibers initiated by the ferric chloride-thiourea redox system has been investigated in aqueous medium. The rate of grafting was calculated by varying the concentrations of monomer, initiator, and thiourea, the acidity of the medium, and the temperature. The rate of grafting increases significantly with an increase of [FeCl3] up to 1.25 × 10−3Mand thereafter it slows down. The rate of grafting also increases with an increase of [thiourea] and [HClO4] up to 2.5 × 10−3and 23.325 × 10−1M, respectively, and thereafter it decreases. The graft percezage increases with an increase of the monomer concentration. The effect of some inorganic salts, solvents, and surfactants on the rate of grafting has also been investigated.

ISSN:0022-233X    

DOI:10.1080/00222338208056479

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Monosaccharides and polysaccharides are chemically modified when they are subjected to rf plasmas derived from oxygen, nitrogen, or argon. The plasma treatment converts hydroxyl groups within the bulk to carbonyl groups on the order of one per anhydroglucose unit. On the surface, the concentration of carbonyl groups is greater than in the bulk. The activated surfaces formed by the plasma treatments are stable for at least 1.5 h. The observed spectral (IR, ESCA, and ESR) changes of the irradiated samples are the direct result of the plasma and not the secondary result of plasma-activated surfaces reacting with the atmosphere.

ISSN:0022-233X    

DOI:10.1080/00222338208056480

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Quantitative measurements on long-chain branching in polyethylene have not been established. This paper presents a method available for calculating the degree of long-chain branching and the exponent α in the hydrodynamic relation g = Gα(where g is the ratio of the intrinsic viscosities of branched and linear molecules at the same molecular weight, and G is the corresponding ratio of mean square radii of gyration), by means of polymerization parameters, size exclusion chromatography, viscosity measurement, and amount of total unsaturation. The calculation based on our experimental data shows the following, in radical polymerization of ethylene. (1) With reaction pressure and temperature varied, the degree of long-chain branching was 0.5 to 3.7 per 1000 carbons. (2) As for the rate constant for long-chain branching, the activation energy Etrp- Epand the activation volume Δ Vtrp* - ΔVp* were 4.1 kcal/mol and 20 cc/mol, respectively. (3) The value of the exponent α, which is considered to represent the type of branching, was independent of reaction pressure and decreased with an increase of reaction temperature, and it was between 0.9 to 1.5, centering around 1.1. The validity of these values in (1), (2), and (3) and the type of branching are discussed.

ISSN:0022-233X    

DOI:10.1080/00222338208056481

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Thermal decomposition of plasma-polymerized hexamethyl-cyclotrisilazane (PP-HMCTSN) thin films was studied by using various techniques. Pyrolysis-gas chromatography investigation of thermal decomposition products and IR examination of the polymer films showed that methylsilyl groups present in the monomer were highly susceptible to form disilymethylene and disilyethylene cross-linkages under plasma conditions. A three-stage mechanism of the thermal decomposition found by thermogravimetry proved a great complexity of the thermal reactions which occur during this process and, in turn, provided strong evidence for a very complex structure of plasma polymer. Electron microscopy investigation revealed a marked effect of the thermal decomposition process on the film microstructure. The trend observed in the morphological changes was consistent with kinetics of this process. The high temperature thermal treatment reduced the organic content of polymer film, correspondingly increasing its inorganic character. Films produced with this process were of unusually interesting properties, displaying strong adhesion to metal substrates and high resistance to corrosive agents.

ISSN:0022-233X    

DOI:10.1080/00222338208056482

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

By the methods of classical and oscillographic polarography, electrolysis with controlled potential and spectrophotometry, the mechanism of electrochemical generation and the active centers nature of anionic polymerization of methyl methacrylate in dimethylformamide was investigated. It was shown that in dimethylformamide in the presence of tetraalkylammonium cations, methyl methacrylate carbanions exist as solvately divided ion pairs in which the electrostatic interaction is determined by the radius of the cation. It affects the chemical stages rate of the electrochemical generation of carbanions and appears by the anomalous shift of ζ 1/2 of polarographic reduction with the increasing of the cation radius of the supporting electrolyte. The replacement of the lithium cation with tetraalkylammonium changes the interaction type of methyl methacrylate carbanion with the counterion.

ISSN:0022-233X    

DOI:10.1080/00222338208056483

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Three samples of poly[2,2′-(o-phenylene]-5,5′-bibenzimidazole] (PBI) were prepared by condensation of 3,3′-diaminobenzidine (DAB) with, respectively, phthalic anhydride in p-cresol under NZ, with phthaloyl chloride in a xylene-water system containing carbonate, and with phthalimide in polyphosphoric acid. Solutions of these PBI samples in formic acid exhibited an anomalous dependence of the reduced viscosity on concentration. This poly-electrolyte behavior of the polymer solution was analyzed by application of empirical relations. The intrinsic viscosity of the PBI samples was measured in formic acid containing 1% (w/v) KBr. A solution of the N-methyl derivative of a PBI (melt) sample showed normal behavior in a viscometric study. The results of DTA of three PBI samples, one N-methyl PBI (melt) sample, and three model compounds are compared and analyzed with a view to estimating the energy of activation and the order of degradation reaction.

ISSN:0022-233X    

DOI:10.1080/00222338208056484

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Ring-scission polymerization of simple and bz-nitro and bz-chlorosubstituted isatoic anhydrides is studied in the presence of reagents like aqueous HCl, anthranilamide, N-methyl aniline, o-chloroaniline, and acid amides under various reaction conditions. Only simple isatoic anhydride is found to undergo ring-scission polymerization affording polyanthranilides in the presence of the first four reagents under appropriate conditions. These samples are insoluble in all organic solvents including formic acid. They are characterized by IR spectral study and thermogravimetric and differential thermal analysis.

ISSN:0022-233X    

DOI:10.1080/00222338208056485

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor