ISSN:0022-233X    

DOI:10.1080/00222337908056698

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The polymerization of acrylonitrile (AN) initiated by 1,4-dimethyl-1,4-bis(p-nitrophenyl)-2-tetrazene (Ie) was studied in dimethylformamide (DMF) at high temperature. The polymerization proceeds by a radical mechanism. The rate of polymerization is proportional to [Ie]0.64and [AN]1.36. The overall activation energy for the polymerization is 21.5 kcal/mole within the temperature range of 115-130°C. The chain transfer of Ie was also undertaken over the temperature range of 120-135°C. The activation parameters for the decomposition of Ie at 120°C are kd= 2.78 × 10−6sec−1, ΔH‡= 40.8 kcal/mole, and ΔS‡= 19.5 cal/mole-deg, respectively.

ISSN:0022-233X    

DOI:10.1080/00222337908056699

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Quantitative measurements on the rate constant for long-chain branching in radical polymerization of ethylene have not yet been cited. This paper presents a convenient method of calculating the ratio of the rate constant for long-chain branching to that for propagation, by means of polymerization parameters, average degrees of polymerization (Xnand Xw), and amount of total unsaturation. The results of calculation based on our experimental data show that the activation energy Etrp-Ep, and the activation volume ΔVtrp*-ΔV *pwere 3.6 kcal/mole and 24 cc/mole, respectively, in radical polymerization of ethylene. The validity of these values is discussed.

ISSN:0022-233X    

DOI:10.1080/00222337908056700

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Radical copolymerization of styrene (M1) with methyl methacrylate has been carried out in several solvents. The monomer reactivity ratio (r) was affected by the solvent. The values of log 1/r, Q2, and e2were found to increase with the decreases of theVC˭Oandvn˭cstretcning frequencies determined in the corresponding solvents.

ISSN:0022-233X    

DOI:10.1080/00222337908056701

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

A study of the radical copolymerization of methyl methacrylate and 1-naphthyl methacrylate in benzene, chlorobenzene, and o-dichlorobenzene was made at 50°C. There is a marked effect of solvent on both r1and r2in all these systems, which can be correlated with the variation in the polarity of solvents. The glass transition temperatures of copolymers were discussed taking into consideration the sequence distribution of the copolymers and the homopolymers tg - values.

ISSN:0022-233X    

DOI:10.1080/00222337908056702

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The influence of various solvents on the copolymerization behavior of methyl methacrylate with styrene has been investigated. In these systems there is a significant solvent effect on both rSand rMwhich may be attributed to changes in the dielectric constant of the solvents used. The calculated relative reactivity of the polystyryl radical towards the methyl methacrylate monomer increases with increasing solvent polarity, whereas the reactivity of poly(methyl methacrylate) radical towards styrene monomer decreases. The results obtained are discussed taking into account the behavior of both monomers in homopolymerization with the same experimental conditions as in copolymerization.

ISSN:0022-233X    

DOI:10.1080/00222337908056703

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Cotton cellulose and other saccharides varying in molecular size and in type of glucosidic linkage were treated with cold plasmas generated by radiofrequency (rf) radiation (13.56 MHz). Plasma treatment produced reactive centers on all compounds, and activated samples were capable of producing chemiluminescence (CL). CL was greatest for long-chain structures. Subsequent immersion of plasma-activated compounds in either CHCl3/CH3OH, or the 2:1 v/v mixed-solvent system (CHCl3/CH3OH) increased CL significantly, with the latter solvent and the large molecules exhibiting the greatest effect. Reagents that caused an increase in CL reduced intensity of the ESR (electron spin resonance) signal, indicating a possible dependence of CL on the decay of free radicals formed during plasma treatment. CL quenched by nitrogen gas was partially regenerated when nitrogen was exchanged with oxygen. CL decay curves showed an initial fast rate followed by a slower one and especially in case of large molecules indicated that at least two different excited states were responsible for observed CL. Consideration of molecular structures of saccharides in relation to CL and to previously reported changes in ESR, IR, and ESCA spectra leads to the conclusion that the glucosidic bond is the primary site of free-radical formation.

ISSN:0022-233X    

DOI:10.1080/00222337908056704

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Acrylamide was polymerized in aqueous solution at 35 ± 0.2°C with the redox pair potassium permanganate/lactic acid. The kinetics of polymerization was followed iodometrically. The effect of monomer, potassium permanganate, and lactic acid concentration and temperature on the rate of polymerization was studied. The dependence of the number-average degree of polymerization on the initial rate of polymerization and temperature was also determined.

ISSN:0022-233X    

DOI:10.1080/00222337908056705

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Bromoform delays the onset of the gel effect of MMA and decreases the acceleration rate in the autoaccelerated region. The first effect can be quantitatively related to the decrease in molecular weight of the produced polymer. The decrease in acceleration shows the dependence of the termination rate constant, in the accelerated region, on the mean size of the growing macroradicals.

ISSN:0022-233X    

DOI:10.1080/00222337908056706

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The graft copolymerization of methyl methacrylate onto silk fibers in aqueous solution with the use of manganese (IV) ions as initiator was investigated. The rate of grafting was determined by varying monomer, acidity of the medium, temperature, nature of silk, and the reaction medium. The graft yield increases significantly with increase of manganese (IV) concentration up to 15 meq/liter; with further increase of manganese (IV) concentration, the graft yield decreases. The effect of the increase of monomer concentration brings about a significant enhancement in the graft yield up to 7%, and with further increase of monomer concentration the graft yield decreases. The graft yield is considerably influenced by chemical modification prior to grafting. The effect of some inorganic salts and anionic surfactants on the rate of grafting has been investigated.

ISSN:0022-233X    

DOI:10.1080/00222337908056707

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor