摘要:

A new graphically-evaluable linear method is suggested for the determination of the reactivity ratios of copolymerization. The proposed new equation is very well adaptable for visual determination of the applicability of the copolymer composition equation. If the experimental data are adequate to the composition equation, the procedure offers a simple and reliable method for the graphical determination of copolymerization constants.

ISSN:0022-233X    

DOI:10.1080/00222337508068644

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Vinyl acetate and maleic anhydride are known to give 1:1 alternating copolymerization regardless of the monomer feed composition. The existence of a charge transfer complex between the comonomers has been shown and its equilibrium constant determined.

ISSN:0022-233X    

DOI:10.1080/00222337508068645

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The study of methacrylic anhydride has shown that the intramolecular propagation step has a higher energy of activation (2.6 ± 0.3 kcal/mole) than the intermolecular step. Steric factors have, however, been found to favor cyclization (A11/Ac= 0.0039 liter/mole). It has been concluded that the conditions which favor cyclization in methacrylic anhydride are high temperature, low monomer concentration, poor solvent system, and high conversion. The increase in cyclization caused by heterogeneous conditions, such as poor solvent or high conversion, appears to be due to tight coiling of the polymer chain and slow diffusion, thereby decreasing the value of k11with respect to kc. Although methacrylic anhydride does cross-link to some extent, the number of cross-links was lower than expected due to anhydride interchange of pendent units. Also, even though some cross-links were present, the polymer could be dissolved due to interchange of the intermolecular cross-links to intramolecular anhydride units. The bathochromic shift observed for methacrylic anhydride, when its UV spectrum was compared with those for the methacrylate esters, was found to result from added electronic stabilization of the α, β-unsaturated system through resonance of the nonbonded electrons on the acyl oxygen with the carbonyl unit attached to it. In a stereochemical configuration study on methacrylic anhydride, no solvent effect could be found. The influence of increasing temperature and conversion was found to be small, but appeared to increase the heterotacticity and decrease the syndiotacticity by equivalent amounts. Noncyclic anhydride units resulted in increased syndiotactic character. The tacticities observed were explained on the grounds of a random cyclic propagation step and a stereospecific intermolecular step. The results of the model study on methacrylic anhydride have been combined with the literature pertinent to the mechanism and stereochemistry of cyclopolymerization in order to develop a general understanding of these areas. After thorough consideration, it seems that the driving-force for cyclization in cyclopolymerizations is due to: 1) statistical probability, 2) thermodynamic stability, and 3) steric and entropy effects. In many dienes, nonconjugated excited state interactions are also very important. The driving force for the higher degrees of polymerization, observed in cyclopolymerization for difficultly polymerizable systems, may be due to steric factors. Stereochemical studies have shown that the high degrees of order which are observed in cyclopolymerization are due to the cyclic units that are formed. It also appears that free radical cyclopolymerizations yield the kinetically controlled product while the alkyl-metal coordination catalysts give the thermodynamic product.

ISSN:0022-233X    

DOI:10.1080/00222337508068646

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The microstructure of polyisoprenes prepared in hydrocarbon solvents with n-butyllithium is very sensitive to pressure, whereas in oxygenated solvents the structure remains unchanged even in the highest pressure range. Thus in n-heptane the content of 1,4-cis units decreases with increasing pressure, leading to polymers with heterogeneous structure. It is assumed that electrostatic as well as steric effects must be taken into account together: pressure acts like a polar solvent; however, in the transition state, steric effects affect the 1,4-cis addition.

ISSN:0022-233X    

DOI:10.1080/00222337508068647

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

ISSN:0022-233X    

DOI:10.1080/00222337508068648

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

This paper reviews the subject of cyclopolymerization with emphasis on the reaction mechanism and the structures of the resulting polymers. In general, the structures have been postulated on the assumption that the reaction products are the result of thermodynamic control, no consideration being given to the possibility of kinetic control. Consequently, the majority of polymers are believed to contain six-membered ring units, often with little supporting evidence. The amount of unsaturation present and the number of uncyclized units is also the subject of ambiguous evidence.

ISSN:0022-233X    

DOI:10.1080/00222337508068649

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

ESR spectra have been recorded for a number of radicals generated in a flow cell by interaction of diallylmalonic acid, diallyl ether, diallylamine, and related compounds with amino, hydroxyl, and phenyl radicals in aqueous solution. The results indicate that the radicals initially formed by homolytic addition at one of the double bonds in the diolefins rapidly undergo cyclization to afford product radicals containing five-membered rings.

ISSN:0022-233X    

DOI:10.1080/00222337508068650

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The reaction of a series of diallylamines and related compounds with free radicals in aqueous acid solution has been studied in a flow system using ESR spectroscopy. The initiation was by radicals generated from titanium trichloride-hydrogen peroxide (hydroxyl radicals) and titanium trichloride-hydroxylamine (amino radicals) systems, respectively. The observed ESR spectra were assigned to five-membered ring radicals as the major radical species present in the system. However, the dimethallyl-amine series gave both five - and six-membered ring radicals.

ISSN:0022-233X    

DOI:10.1080/00222337508068651

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The azobisisobutyronitrile-initiated polymerization of various N-substituted diallylammonium, N-ethyldimethallylammonium, and triallylammonium chlorides yielded as the respective major by-products 2-substituted 6, 6-dimethylperhydro-5-isoindolones, 2-ethyl-3a, 6,6,7a-tetramethylperhydro-5-isoindolone, and 2-allyl-6,6-dimethylperhydro-5-isoindolone. These isoindolones are formed from pyrrolidylmethylene radical precursors and indicate that, in agreement with recent ESR studies, radical addition to diallylamines results in the formation of pyrrolidine derivatives and not piperidines as previously supposed. The reactions of azobisisobutyronitrile and azobisis-obutyramidine dihydrochloride with the models, N,N-dimethylallylammonium and N,N,2-trimethylallylammonium chlorides, are also described.

ISSN:0022-233X    

DOI:10.1080/00222337508068652

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

A study of the13C chemical shift data and of the shifts induced by Eu(dpm)3has shown that the aminoketone formed in the reaction of N-methyl-N,N-diallylamine with cyanoisopropyl radicals is 2,6,6-trimethyl-cis-perhydroisoindolid-5-one (1a, R = O). The13C NMR spectrum in the presence of acid reveals the existence of two protonated forms of this compound.

ISSN:0022-233X    

DOI:10.1080/00222337508068653

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor