摘要:

AbstractThe infrared spectra of synthetic polyisoprenes have been used to obtain quantitative analyses for the various types of addition occurring in the polymers. It is found that the composition of polymers prepared in bulk and emulsion systems is, within experimental error, independent of specific catalyst and per cent conversion of monomer to polymer. The structure of these materials is affected by preparation temperature, increasing temperature leading to a slight increase in 3,4 addition and a large increase incis1,4 addition. Polymers prepared in solution with alfin and sodium catalysts show increased amounts of 3,4 addition at the expense of 1,4 addition. Polymers prepared with a cationic catalyst (BF3) are apparently not exclusively linear polyisoprenes.

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100401

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractThe molecular weight of selected polyvinylpyrrolidone samples was determined by light scattering and by osmotic pressure in methanol. The corresponding limiting viscosity numbers were also determined, as well as the limiting viscosity number of the same samples in water. The data relating to the methanolic system conform with theory and the values forKand α in [η] =KMαwere determined. The data relating to aqueous solutions do not show such conformity but an unexplained dependence on the degree of homogeneity of the samples. Nevertheless some empirical constants were deduced which may aid in industrial practice in which aqueous viscosity measurements are usu

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100402

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractNew evidence bearing on the resistance to hydrolysis of a portion of the amide groups in polymethacrylamide has been obtained through a study of methacrylic acid (M1) — methacrylamide (M2) copolymers. These copolymers were prepared in aqueous solution with potassium persulfate catalyst. The reactivity ratios were found to be approximately r1= 2.0, r2= 0.3. The ratio of accessible amide nitrogen to total nitrogen was determined for each copolymer and was found to vary from 62.3% for polymethacrylamide to 4.3% for a copolymer containing 4.2 mole % of the amide. Some calculations have been made based upon a semiquantitative statistical interpretation of the suggestion of Arcus that the hydrolysis of polymethacrylamide ceases as soon as each amide group is bordered by two carboxylic ion neighbors and the agreement between observed and calculated ratios offers good support for this theory. The actual mechanism of stabilization by the ion neighbors is still obscure but the chain‐stiffening effect of the α‐methyl groups is believed to play an importan

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100403

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractReaction curves for the simplest of cellulose acetylation systems; namely, the homogeneous reaction of secondary cellulose acetates with acetic acid and water, were studied. These reactions were found to be slow and complex, consisting of two interdependent simultaneous reversible second‐order processes. The faster process represented the reaction of primary hydroxyl and acetyl groups, while the slower process represented the reaction of the two secondary hydroxyl and acetyl groups. Equilibrium and rate constants and initial and final concentrations of hydroxyl and acetyl groups were calculated for the two simultaneous reactions. Equilibrium constants for the primary groups favored acetylation, while equilibrium constants for the secondary groups favored deacetylation. Final equilibrium was not affected by the presence of sulfuric acid. On the other hand, rate of reaction was increased in the presence of sulfuric acid, indicating catalysis by this reagent. The reaction mechnanism outlined above was confirmed by comparing primary hydroxyl group contents calculated from acetylation results with primary hydroxyl group contents measured by means of the tritylation reaction. Energies of reaction and energies of activation were calculated. Energies of reaction were low, indicating that equilibrium for this process is very nearly temperature independent. Energies of activation were in agreement with energies of activation for esterifications of simple alcohols, from which it was concluded that the acetylation and deacetylation of secondary cellulose acetates in homogeneous solution is but another example of general acid catalyzed esterification with carboxylic acids and general acid catalyzed hydrolysis of fatty acid esters. Degradation of the cellulose chain molecule was followed throughout these studies and energies of activation for this reaction were calculated. These energies of activation were higher than those for the acetylation reactions. It was concluded that degradation is more severe at higher temperatures for a given change in acetyl group substitution. Initial determination of equilibrium and rate constants for acetic acid acetylation of cellulose acetate has been carried out. It is suggested that through use of such procedures as tritylation analysis, which isolates the reaction of the primary groups from the secondary groups, improved values for these constants may be achieve

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100404

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractLes fonctions de diffusionP(ϑ) des molécules linéaires, présentant un degré de rigidité variable et caractérisées par une logueur permanentea(comme définies par Kratky et Porod) ont été calculées;aest défini comme étant la projection d'une chaîne infiniment longue dans la direction du premier segment moléculaire. Les résultats sont obtenus sous la forme de développements en série valables pour des degrés de flexibilité moyens à élevés. On montre que les fonctions de diffusion ainsi obtenues sont comprises entre celles correspondant à un bâtonnet rigide et à une pelote statistique. En outre, les auteurs indiquent une méthode qui permet d'obtenir les paramêtres moléculairesa, la longueurLet le diamètre de la spireRaux dép

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100405

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractA discrepancy between the previously reported viscosity‐weight‐average molecular weight relationship obtained for fractionated polymethylmethacrylate in acetone and that given by Meyerhoff and Schulz is attributed to the great influence of small chemical inhomogeneities on the molecular dimensions in the poor solvent acetone. Light‐scattering results for the root‐mean‐square end‐to‐end distanceRhave been recalculated, taking into account a correction pointed out by Oth. It is shown that the results are in excellent agreement with the relationR3=M[η] 2.1 × 1021proposed by Flory and Fox, rather than theM1/2dependence predic

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100406

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100407

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100408

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100409

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100410

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY