摘要:

In order to assess the possibility of isomerization during radical polymerization of vinyl mercaptobenzothiazole (VMBT), the isomerization of VMBT and its related compounds was investigated in the presence or absence of catalyst. In the absence of catalyst, VMBT was found to polymerize through participation of only its vinyl group at temperatures below 200°C. When VMBT was heated at 200°C in the presence of iodine as a catalyst, mercaptobenzothiazole (MBT) and polymer containing both a double bond and the benzothiazolinethione unit were obtained, but no isomerized N-vinyl monomer (VBTT) was produced. However, ethyl mercaptobenzothiazole (EMBT), a saturated model of VMBT, was easily isomerized to N-ethyl benzothiazolinethione under the same conditions. Therefore, it was concluded that VMBT was polymerized by the ordinary vinyl polymerization mechanism, even at 200°C without isomerization, but the MBT group in the resulting VMBT polymer underwent isomerization and elimination if isomerization catalyst was present.

ISSN:0022-233X    

DOI:10.1080/00222337908058153

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The polymerization of acrylonitrile (AN) initiated by tetramethyl-2-tetrazene (TMT) and p-toluenesulfonic acid (TSA) in dimethylformamide (DMF) was studied. The polymerization was confirmed to proceed through a radical mechanism. The initial rate of polymerization R was expressed by the equation: Rp= k[TMT]0.6[TSA]0.46[AN]1.35. The overall activation energy for the polymerization was estimated as 20.7 kcal/mole. In the absence of monomer, the reaction of TMT with TSA was also studied kinetically by measuring the evolution of nitrogen. From these results and ESR measurement of the TMT/TSA system, a possible initiation mechanism is proposed.

ISSN:0022-233X    

DOI:10.1080/00222337908058154

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The kinetics of aqueous polymerization of acrylamide with the Cu2+/metabisulfite redox system has been studied in an atmosphere of nitrogen at 35 ± 0.2°C. The rate of polymerization has been found to be second power on monomer concentration, zero and 0.5 power with respect to catalyst, and 0.5 power with respect to activator concentration. The molecular weight of the polymer has been found to increase with the increase in the concentration of monomer. Catalyst has been found either to increase or decrease the molecular weight of the polymer formed, depending largely upon the fixed concentration of activator. The overall energy of activation has been calculated to be 24.95 kcal/deg.-mole between 35 and 50°C.

ISSN:0022-233X    

DOI:10.1080/00222337908058155

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Long chain monomers such as hexanediol diacrylate (HDDA) trailed in canals various monomers of relatively large size to form urea canal complexes. The relationship between the monomer composition and copolymer composition after in-source copolymerization and post-copolymerization of irradiated HDDA and the second monomers (styrene and methacrylonitrile) in urea canal was investigated. With in-source copolymerization at 25°C, the content of the second components in the polymer was far larger than that in the monomer feed, while, in post-copolymerization at elevated temperatures, the ratio of the two components in the polymer nearly agreed with their ratio in the monomer mixture.

ISSN:0022-233X    

DOI:10.1080/00222337908058156

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

A glass transition temperature (T) study on poly-α-methyl-styrene samples having bimodal molecular weight distributions composed of components D + A and B + C, was carried out with a DSC-2 differential scanning calorimeter. T data were also collected on binary blends of poly-α-methylstyrene samples prepared from narrowly dispersed low and high molecular weight polymers. Extrapolated Tge(at q = 1°K/min) data of the bimodal polymers showed that the percent proportion, the molecular weight [Mbar]n, and the steric configuration of component D + A play an important role in determining their overall glass transition temperatures, these being lower than those recorded for a unimodal polymer of the same [Mbar]n. In binary blends of poly-α-methylstyrene, the overall glass transition is not affected by the presence of the low molecular weight component either because its steric structure differs with that of D + A or because of the fact that in binary blends the chain-end segments of the two components are not well packed.

ISSN:0022-233X    

DOI:10.1080/00222337908058157

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The feasibility of chemical bond formation, especially in the chain-transfer reaction between polymer and β-cyclodextrin (β-CD) molecules in the products of the radiation polymerization of β-CD with vinylidene chloride (VDC) its adducts has been considered. The lack of these bonds in the polymerization products of similar β-CD adducts with methyl methacrylate (MM), styrene (St), a mixture of VDC and allyl chloride (AC) and a mixture of VDC and MM (10:90 molar ratio) has been established. On the basis of the results obtained the lack of chemical bonds in the polymerization product of β-CD· VDC adduct is suggested.

ISSN:0022-233X    

DOI:10.1080/00222337908058158

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The investigations of the synthesis of polyrotaxanes by the radical polymerization of monomers (vinylidene chloride, methyl acrylate, styrene, and methacrylonitrile) in DMF in the presence of β-cyclodextrin have been carried out. The possibility of formation β-cyclodextrin inclusion compounds with some vinyl monomers or some other organic substances in DMF solution has been established. We assume that the inclusion in presence of the solvent is related to the unusual phenomenon of β-cyclodextrin crystallization in hot DMF solutions. The polymerization of vinyl monomers in DMF solution at increased temperatures in the presence of β-cyclodextrin leads to compounds containing a great amount of cyclic compounds (up to 80%). Similar results have been obtained for monomers introduced as previously prepared adducts with β-cyclodextrin. Stable compounds of polymer and β-cyclodextrin have been obtained in the case of vinylidene chloride. The lack of carbohydrate moieties in the product obtained by polymerization of vinylidene chloride in the presence of linear dextrin suggest the inclusion character of the linkage between polymer and β-cyclodextrin molecules. The structure of a topological compound of polyrotaxane type is most feasible after dehydrochlorination.

ISSN:0022-233X    

DOI:10.1080/00222337908058159

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

It was shown that the difference in the polymerizability of a series of allyl monomers, e. g., vinylacetic acid, allyl acetate, dimethylvinylcarbinol, diallyl ether, allyl alcohol, dimethyl-allylamine, diallylamine, and allylamine is related to the polar effects of the functional groups, whose influence determines the relative stability of the C-H bond at the α-position and thus the rate of the chain transfer to the monomer (degradative chain transfer) as the result of this effect. The initial polymerization rates obey the Hammett-Taft equation, log (1/V0) = const + ρσ°, where ρ is equal to −2. The study of the effect of different acids on polymerization kinetics of allyl monomers and molecular weights of products has revealed that the increase in polymerization rate depends on the nature of monomer, molar ratio of acid and monomer, and the nature, functionality, strength, and concentration of the acid. A kinetic scheme was proposed to determine the contribution of different factors into the overall effects. From the determination of kinetic parameters, one can see that the stronger the link between proton and the group X, which ultimately depends on the basicity of monomer, the more the value of the constant of the chain transfer rate to the monomer is decreased as the result of protonation. The second factor which is responsible for the increase in polymerization rate is the conversion of degradative chain transfer into effective chain transfer. This is proved by showing that the value of probability of initiation of the chain transfer with allyl radicals CH2˭CH‒ĊH‒X is close to 1. Correlation was found between the polymerization rates of protonated monomers and pK values which characterize the nucleophilicity of the group X.

ISSN:0022-233X    

DOI:10.1080/00222337908058160

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

A polybenzyl polymer which formed in the reaction of benzyl salicylate and phosphorus (V) chloride originates from the self-condensation of benzyl chloride catalyzed by the phenyl-phosphorodichloridate (I). A chromatographic procedure for purification of the polybenzyl polymer has been developed. Equations for calculating degree of polymerization from1H-NMR spectra of polybenzyl polymers are derived on the basis of the presence of CH2Cl terminal groups. Generalized structural formulas which delineate the difference between linear and branched polybenzyl polymers are proposed. Relationships between the idealized polybenzyl polymers and maximum degrees of polymerization are suggested.

ISSN:0022-233X    

DOI:10.1080/00222337908058161

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

A kinetic study of the reaction of o-cresol with formaldehyde was carried out at temperatures of 65 ± 0.05, 70 ± 0.05, 75 ± 0.05, and 80 ± 0.05°C with NaOH as catalyst. The pH maintained was 7, 8, 9, 9.4, and 10. The reaction follows a second-order rate law. The rate is found to increase with increase of pH. The overall rate constant k was resolved into stepwise rate constants (k1and k2) for the formation of mono-methylol-o-cresols and dimethylol-o-cresol, respectively. The values of Arrhenius parameters and the entropy of activation for the overall reaction were calculated. The experimental and calculated values of k at pH 10 and 65, 70, 75, and 80°C were found to agree well within experimental error.

ISSN:0022-233X    

DOI:10.1080/00222337908058162

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor