摘要:

AbstractThe formation of quinonedimethide monomers by pyrolysis of the corresponding dimethyl hydrocarbons has been described by Szwarc in a number of publications. Under certain conditions, the monomers so produced may polymerize to high molecular weight products which are of considerable interest. Some dimethylated hydrocarbons do not, however, appear to from monomers under these conditions, and the products of pyrolysis vary considerably with hydrocarbons of different structure. In this communication, the energetics of the various reactions leading to formation of radicals, quinonedimethide monomers, and products of their dimerization or disproportionation are briefly discussed theoretically. The kinetics of the most probable reaction sequences are discussed in the light of the energetic data, and it is shown that a number of features of results so far obtained can be understood in terms of this preliminary treatment. It is hoped that this approach will prove useful as a guide to the types of reactions to be expected for aromatic hydrocarbons of differing π‐electron structu

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110401

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractAddition of its polymer causes methyl methacrylate to polymerize. The extent of polymerization is linear with time of reaction to at last 5% conversion at 60–90°C. The rate of polymerization is proportional to the first power of the concentration of added polymer and independent of its molecular weight. The molecular weight of the polymer formed increases with increase in reaction temperature. No polymerization caused by polymer occurred with the other polymer/monomer systems tested. The rate and nature of the initiating reaction are discuss

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110402

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractThe gutta isolated from chicle has been demonstrated to be structurally identical withtrans‐polyisoprene from gutta percha and balata but has a molecular weight of 16,000–18,000, about one‐half that of the latter two polymers. Its ease of purification and marked crystalline behaviour suggested its use in a study of gutta polymorphism.The α‐and β‐forms of chicle gutta were prepared and their identities were established by means of x‐ray diffraction measurements and melting properties. The degree of crystallinity and internal molecular strain were shown to affect the melting points of the two forms of gutta through wide ranges. Interconversions of α‐and β‐guttas were effected by means of heat conditioning, solution and reprecipitation, melting and resolidification, and treatment of the gutta with nonsolvents. Dilatometric data were used to describe the change of specific volume when β‐gutta was converted to α‐gutta in a conditioning bath as the temperature was increased stepwise from 30°C. to 80°C. at the rate of 1°C. per hour. The discontinuous, saw‐toothed nature of the specific volumevs.time curve was rationalized on a basis of reactions involving changes in degree of molecular order and relief of strain within the gutta. The curve suggested the following gross reactions: 30–36°C., thermal expansion of β‐gutta of low crystallinity; 36–52°C., increase in degree of crystallinity of β‐gutta; 52–60°C., melting of β‐gutta; 60–64°C., transition of β‐ to α‐gutta; 64–72°C., melting of α‐gutta; 72–80°C., thermal expansion of molten gutta. α‐Gutta, in the melted condition, was shown to undergo a transition, above 72°C., to a form whose stereo identity has not yet been established. The rate of transition from β‐to α‐gutta at temperatures at which α

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110403

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractThe steady state method is applied to the benzoyl peroxide initiated polymerization of styrene in toluene at 80°C. The reaction mixture is kept homogeneous by stirring. A theoretical discussion shows that the time needed to reach the steady state concentrations with an accuracy of 1% or better is about seven times the average time which the mixture spends in the reaction vessel; this is confirmed by experiment. The experimental results show that the rate of polymerization can be represented by the formula:\documentclass{article}\pagestyle{empty}\begin{document}$$ - dm/dt = kmE^{1/2} ;E = \beta m(1 + \beta m)^{- 1} $$\end{document}wheremis the monomer concentration, whilekand β are constants. It is found that β = 1.19 liter/mole. The apparent order of the reaction, with respect to monomer, increases from 1.18 whenm= 1.8 mole/liter to 1.36 whenm= 0.4 mole/liter. An analysis of the limits of experimental error indicates that in the conventional method this change in apparent reaction order would have been of the same order of magnitude as the experimental error. The accuracy of the steady state method, however, is sufficient to establish this change unambiguously. Numerous data from the literature concerning the polymerization of styrene and other monomers are discussed, and are found to be in good agreement with the conclusions reached in the present work. Explanations are offered for a number of discrepancies found in the literatu

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110404

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractThe thermal degradation of polystyrene has been studied in naphthalene solutions in high vacuum. The rates of loss of weight have been determined over a range of temperatures from 350 to 380°C., and the energy of activation has been derived. Also the decrease in intrinsic viscosity with time and the loss of weight as function of polymer concentration have been investigated. The mechanism of degradation in naphthalene solution is similar to that of the thermal bulk degradation; it consists of an initial random chain scission process due to weak links, followed by a reverse polymerization process with chain end initiation

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110405

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractRates of adsorption from solution on to charcoal and adsorption isotherms have been determined for unfractionated and fractionated polystyrene samples. The rates and extent of adsorption increase with decreasing solvent power and decreasing molecular weight. The rate curves of the fractionated samples show two distinct steps. Langmuir's adsorption equation is obeyed. Mechanisms of adsorption are discussed.

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110406

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110407

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110408

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1953.120110409

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY