摘要:

AbstractA derivative of wool keratin dissolved in a strong solution of urea was examined in the ultracentrifuge and by diffusion methods. The solution was polydisperse, yielding a single broad peak in the ultracentrifuge. Approximate molecular constants were calculated to bes 2001.93,D20m= 1.9 × 107,M= 84,000,f/f0= 3.8. The molecule is very asymmetrical, which is in accord with the fiber‐forming properties of the derivative. On further reduction the molecular weight falls to ca. 8000 and the molecule shortens. It is suggested that the fully reduced solution (M.W. = 8000) is that of the primary polypeptides of wool keratin and that the longer and larger molecules (M.W. = 80,000) are formed by the combination of the primary chains effected by disulfide bri

ISSN:0022-3832    

DOI:10.1002/pol.1951.120060601

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

摘要:

AbstractExcellent reproducibility of an emulsion polymerization of styrene has been obtained in a nitrogen atmosphere and a technique and apparatus have been described to obtain this reproducibility. The rate of polymerization for this system has been shown to be proportional to the square root of the catalyst concentration and to increase with higher catalyst concentrations. Average molecular weights were higher with higher concentration of catalyst within the catalyst concentrations studied and polymerization occurred without significantpH changes.In contrast, reproducibility of the emulsion polymerization in air atmosphere was unsatisfactory. The presence of air (oxygen) increased the induction period, decreased the rate of polymerization and decreased the average molecular weight of the polymer. Since the time necessary for polymerization was increased, the decrease inpH was considerable during the polymerization.

ISSN:0022-3832    

DOI:10.1002/pol.1951.120060602

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

摘要:

AbstractEmploying a reproducible system for the emulsion polymerization of styrene it has been demonstrated that agitation (stirring or shaking) affects both the rate of polymerization and maximum average molecular weight of the polymer formed. Increasing the agitation increases the inhibition, decreases the polymerization rate, and lowers the average molecular weight of the polymer formed. Agitation affects both a peroxide and a persulfate catalyzed polymerization in a similar manner. Agitation effects have been observed in the presence of a redox system and in the presence of a chain modifier. Oxygen has been demonstrated to stop as well as inhibit the initiation of an emulsion polymerization.

ISSN:0022-3832    

DOI:10.1002/pol.1951.120060603

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

摘要:

AbstractSwelling and solubility characteristics of polyvinyl alcohol and polyvinyl alcohol–acetate copolymers in liquid water have been examined. For a given species, swellings are found to be variable in a continuum of metastable states depending on the previous history of the polymer. Changes in swelling are induced in a predictable manner by treatments such as humidification. Changes are interpreted in terms of cumulative secondary bond cross‐linkages arising from the development of microcrystalline regions within the

ISSN:0022-3832    

DOI:10.1002/pol.1951.120060604

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

摘要:

AbstractThe formation of polymers from diolefins and dimercaptans has been extended to some new monomer combinations to yield strong, slightly elastic fibrous polymers which contain groups that permit subsequent cross‐linking. Osmotic molecular weight data have been obtained on a variety of polymers with different inherent viscosities. Polymers with a molecular weight of 60,000 have been obtained from biallyl and hexamethylenedithiol.Diallyl sulfide has been found to be relatively unreactive toward the addition of a mercaptan under the conditions used. This indicates that a sulfur atombetato the double bond interferes with the free radical‐catalyzed addition of a mercaptan. The basecatalyzed reaction of hexamethylenedithiol and the cross‐conjugated dienone, dibenzalacetone, has yielded a rubbery‐type

ISSN:0022-3832    

DOI:10.1002/pol.1951.120060605

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

摘要:

AbstractPure 4‐vinylcyclohexene and hexamethylenedithiol react under a variety of conditions to produce a polymer which has factice‐like properties. The polymers with the highest inherent viscosity were prepared in MP‐189‐EF emulsion at apH of 4 with a persulfate–bisulfite–copper sulfate initiator. The polymers are readily cross‐linked, and if dried without careful removal of initiator solution, they show properties of vulcanized factice samples. Bisazoisobutyronitrile, a cumene hydroperoxide–ferrous pyrophosphate system, and a ceric sulfate–bisulfite copper system have also been used to initiate this polyme

ISSN:0022-3832    

DOI:10.1002/pol.1951.120060606

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

摘要:

AbstractIn polymerizing styrene at room temperature in the presence of tin tetrachloride, it is found that the rate of polymerization is greatly affected by the dielectric constant of the medium. It increases by a factor of approximately 1400 when the dielectric constant changes from 6.5 to 18.4. At the same time the degree of polymerization increases only slightly. The results are interpreted as supporting evidence for the mechanism of Friedel‐Crafts polymerizations as suggested by Polanyi and co‐workers. A unimolecular termination by proton‐splitting cannot be reconciled with these results.Quantitative equations are derived relating the rate and degree of polymerization to the dielectric constant. Traces of liquid water have no visible effect on the polymerization while larger amounts cause retardation. The degree of polymerization, which is of the order of 20, does not change with conversion and is unaffected by the catalyst pr

ISSN:0022-3832    

DOI:10.1002/pol.1951.120060607

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

摘要:

AbstractThe copolymerization of butadiene and styrene in an alkanesulfonic acid emulsion with air as the oxidizing agent and higher alkanesulfinic acids as oil‐soluble reducing agents has been studied. Dodecyl mercaptan and ferric salts are needed to make this recipe function well. The optimumpH for rapid polymerization was found to vary with the different alkanesulfinic acids (C8to C18in the even‐numbered straight‐chain series). Tetradecanesulfinic acid is the most active reducing activator in this series. The conversions with butadiene and styrene are about 75–80% at 30° in six hours and these copolymers have normal solubility and inherent vis

ISSN:0022-3832    

DOI:10.1002/pol.1951.120060608

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

摘要:

AbstractThe number and weight distribution functions, the number and weight average chain lengths, and the inhomogeneities of an initially homogeneous polymer sample have been calculated assuming a mechanism likely to be encountered during the ultrasonic degradation of long‐chain molecules. The evaluation of experimental results on the basis of this mechanism has been indicated and Schmid's theory of ultrasonic degradation has been briefly discusse

ISSN:0022-3832    

DOI:10.1002/pol.1951.120060609

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY

摘要:

AbstractThe degradation by ultrasonic waves of a homogeneous polystyrene sample has been studied. The degradation does not proceed to the monomer but ceases at a definite intermediate chain length. A rate constant has been derived. The experimental size distributions of the polymer at various stages of the degradation have been determined and compared with size distributions derived from the theory of ultrasonic degradation. Satisfactory agreement has been found between experiment and theory for the main features of the degradation.

ISSN:0022-3832    

DOI:10.1002/pol.1951.120060610

出版商:Interscience Publishers, Inc.    

年代:1951

数据来源: WILEY