摘要:

In the butyllithium polymerization of butadiene in aliphatic solvents at 25°C, the first few monomer units are incorporated largely in a 1, 2 manner. With increasing degree of polymerization the extent of 1, 2 addition decreases to a limiting value of about 10% at a degree of polymerization of about 50. However, within this region of high 1, 2-addition increasing solvent basicity, i.e., changing from aliphatic to aromatic solvents, markedly reduces extent of 1, 2 addition and also narrows the molecular weight distribution. Further, in aliphatic solvents, increasing polymerization temperature from 25 to 60°C also results in a marked reduction in 1, 2 addition. These results are consistent with the concept that an ion pair of the associated organolithium complex, [R (n-1Lin] ⊕R⊖, is the active polymerization species and that changes in mode of monomer incorporation are due to changes in the degree of association of the entire organolithium system.

ISSN:0022-233X    

DOI:10.1080/10601326808051433

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The effect of some lithium salts on the microstructures of low-DPpolybutadienes was determined. Lithium alkoxides markedly increased extent of 1, 2 addition, and the increase was a function of the alkoxide/butyllithium ratio. Other salts, such as lithium hydride and lithium hydroxide, had little, if any, effect on polybutadiene micro-structure. The product from the reaction of 1-hexyne and butyl-lithium increased 1, 2 addition and also resulted in polybutadienyl lithium solutions that were very high in viscosity or gelled.

ISSN:0022-233X    

DOI:10.1080/10601326808051434

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

A study of the copolymerization of phenanthrene and maleic anhydride was carried out at 60°C using AIBN as a radical initiator. The copolymerization is characterized by the fact that these two monomers are hardly homopolymerized, and the complex formed by the two monomers may promote the copolymerization. Also, it was found that solvents having no ability to complex with monomer were good milieus for this copolymerization.

ISSN:0022-233X    

DOI:10.1080/10601326808051435

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The cationic polymerization of β-phenylvinyl alkyl ethers (alkyl: methyl, ethyl, n-propyl, and n-butyl) was examined in toluene and in methylene chloride with boron fluoride etherate and with stannic chloride at −78°C. Despite the fact that these monomers have bulky substituents on the α –and β-carbons, they could be homopoly-merized easily even in nonpolar sovent at −78°C. The general features of β-phenylvinyl alkyl ethers in homopolymerization and co-polymerization with n-butyl vinyl ether suggested that β-phenylvinyl alkyl ethers behaved as derivatives of vinyl ethers, not as derivatives of styrenes. The polymerization products were white powders having a high softening point.

ISSN:0022-233X    

DOI:10.1080/10601326808051436

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

o-Methoxystyrene was polymerized under various conditions with BF3 O(C2H5)2, SnC14, or A1(C2H5)Cl2catalyst. The effect of polymerization conditions on the steric structure of poly(o-methoxy-styrene) was studied by NMR spectra of the methoxyl protons, and has been tentatively assigned to the triad tacticity of the polymer. Highly stereoregular polymers were not obtained by these catalysts. The tacticity of polymers was independent of the polarity of solvents, as observed in the cationic polymerization of α-methylstyrene. This behavior was completely different from the cationic polymerization of vinyl ethers. It was found that the heterotactic fraction increased with decreasing polymerization temperature upon polymerization in toluene solution. The fraction of the triad tacticity calculated from Bovey's equation coincided with the experimental results. This fact shows that the steric structure of the addition monomer is determined only by the growing chain end unit and that there is no penultimate effect.

ISSN:0022-233X    

DOI:10.1080/10601326808051437

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

A study of the reaction of tertiary amines with p-methoxy-p'-nitrobenzoyl peroxide in the presence of styrene was made in benzene. Anisic acid and p-nitrobenzoic acid were obtained from the reaction product. Using gas chromatography, the molar ratio of the amount of the above two acids was measured and classified into three types, according to the kind of amine used. From the results the reaction mechanism was discussed, and it was concluded that the oxygen which stands adjacent to the p-methoxybenzoyl group may be charged more positively and may be the more predominantly attacked by tertiary amine.

ISSN:0022-233X    

DOI:10.1080/10601326808051438

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The action of phenylboron dichloride upon ferrocene or ruthenocene in highly concentrated sulfolane solution in the presence of zinc chloride produces soluble polymeric metallocene compounds having phenylboron bridging units in the backbone. Number-average molecular weights are in the approximate range 1200-3500. The polymer structures, which comprise homo- and heteroannularly disubstituted metallocene units and variable populations of cyclo-pentylene groups in addition to phenylboron bridges, arise as a result of competitive reactions believed to involve electrophilic attack by boron on the metallocene and cleavage of the bonds connecting the central Fe or Ru atom with the cyclopentadienyl rings of the metallocene system, this cleavage reaction being followed by polyalkylation steps via intermediary cyclopentenyl cations. The ruthenocene system undergoes metal-ring bond fisson more sluggishly than does ferrocene; hence, the ruthenium-containing polymers possess a lower content of cyclopentylene moieties than determined for the iron-containing counterparts obtained under comparable conditions.

ISSN:0022-233X    

DOI:10.1080/10601326808051439

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Using the theories of random degradation of Montroll and Simha, relationships are derived among limiting viscosity number, degree of degradation, and number-average molecular weight for a polymer undergoing random degradation in a closed system. Relationships among these parameters are derived for initial distributions of the “coupling” and the monodisperse types. Computer programs have been written which rapidly provide reliable values of number-average molecular weights and degrees of degradation from measured viscosity data on polymers with these initial distributions undergoing random degradation.

ISSN:0022-233X    

DOI:10.1080/10601326808051440

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The photolysis of polyvinylpyrrolidone in oxygen-free aqueous solutions has been investigated as a function of polymer concentration, chain length, light intensity, and temperature. Ultraviolet spectra at various degrees of degradation have been measured. The experimental data can be satisfactorily accounted for by a Norrish type II cleavage of main chain links for ketones in conjunction with a small component of type I chain scission yielding polymer radicals. Recombination of double-bond-ended chains with polymer radicals takes place.

ISSN:0022-233X    

DOI:10.1080/10601326808051441

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

It is observed that sodium phosphate polymers, in which some of the Na+ions have been replaced by La3+ions, are subject to both simple molecular flow and to bond interchange in the glass transition region. These two relaxation mechanisms are separated, and their relative contributions to the shear viscosity are calculated. It is shown that the bond-interchange mechanism is subject to an activation energy of ca. 50 kcal, while that of the molecular flow is of the order of 200 kcal at Tg + 30°C;the latter is of the WLF form. It is further shown that the La3+ions act as cross-links, at least at low concentrations, and that bond interchange occurs at the site of the La3+ions rather than at random along the polymer chain.

ISSN:0022-233X    

DOI:10.1080/10601326808051442

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor