摘要:

AbstractPolyester molecules containing free carboxyl end‐groups react with MgO and ZnO as polydendate ligands to form donor–acceptor complexes, followed by the increase in molecular weight of the original polyester. The role of water in these coordination reactions was studied. It was demonstrated that the water can catalyze the reactions by promoting an ionization effect. In some case it can coordinate to the metal compound and effectively compete with the other ligands pres

ISSN:0360-6376    

DOI:10.1002/pol.1974.170121001

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe problem of the complete description of the sequence distribution of units in products of macromolecular reactions is discussed. The exact mathematical solution is proposed based on the muitiplet method and rate constants and including the distribution of reacted units as well as nonreacted units. Various approximate solutions of the same problem, i.e., Markovian approximations of the first, second, and third order and an approach based on the consideration of the kinetics of transformations of the sequences of reacted units (B approximation) are considered. To compare the efficiency of various methods of calculation some characteristics of the distribution of units are estimated following exact and approximate equations at various ratios of rate constants.

ISSN:0360-6376    

DOI:10.1002/pol.1974.170121002

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe stability of disodium tetramer of α‐methylstyrene (“living” polymer) in THF and in a THF‐α‐methylstyrene mixture has been investigated by spectrophotometry. It was found that at 25°C and at concentrations lower than the equilibrium concentration α‐methylstyrene greatly stabilizes the process leading to disappearance of the main absorption band (λmax= 340 mμ) of “living” polymer. In this case isomerization of “living” polymer is accompanied by quantitative conversion of the compound having λmax= 340 mμ into a new compound with λmax= 430 mμ. The constants of the disappearance rateD340and the activation energies of the process were determined in THF and in a THF‐α‐methylstyrene mixture. The introduction of small amounts of α‐methylstyrene into living polymer at 25°C markedly increases its activity in the course of propagation. The experimental results are considered from the standpoint of formation of complexes

ISSN:0360-6376    

DOI:10.1002/pol.1974.170121003

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractN‐Vinylindole (NVI) was copolymerized with such electron‐accepting monomers as fumaronitrile (FN) or diethyl fumarate (DEF) under initiation with a radical catalyst. The compositions of the copolymers varied from 1:1.1 to 1:1.85 (NVI:FN or DEF). The FN or DEF content in the copolymer increased with increase in the molar fraction of the FN or DEF monomer in the monomer feed. It was suggested that both copolymers have a 1:1 recurring unit of NVI and the electron‐accepting monomer, thus being alternating copolymers, and that further addition of the electron‐accepting monomer to the indole ring occurred at its electron‐rich β

ISSN:0360-6376    

DOI:10.1002/pol.1974.170121004

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractIn order to study the effect of conformational changes in electron‐transfer reactions of Co(III)–polymer complexes,cis‐[Co(III)(en)2LCl]Cl2, where the ligand L is PVI(poly‐N‐vinyl‐2‐methylimidazole) or NEI (N‐ethylimidazole), was prepared. Electrontransfer reactions with ferrous sulfate or FeEDTA2−were examined mainly with respect to the effects of the degree of coordination, ionic strength, composition of reaction solvent, in relation to the conformational changes. In the reduction by FeEDTA2−, an increase in the degree of coordination of Co(III)–PVI brought about an extreme increase in its reactivity, while it was almost unity in the reduction by ferrous sulfate. With an increase in the ionic strength, the reactivity decreased due to the electrostatic shielding in the reduction by FeEDTA2−. It was noticed that the reaction of Co(III)–PVI was much more enthalpically disadvantageous due to the shrinkage of the polymer chain than that of Co(III)–NEI, when neutral salts were added. In an aqueous alcoholic solvent, an increase in the alcohol concentration accelerated the reaction with FeEDTA2−, and especially in the reaction of Co(III)‐PVI, the maximum and minimum points of the reactivity were observed. On increasing the reaction temperature, the maximum and minimum points shifted to lower alcohol concentration. These phenomena are discussed in regard to the confor

ISSN:0360-6376    

DOI:10.1002/pol.1974.170121005

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe effects of various polyolefin photostabilizers on the thermal and photodecomposition of model and polymeric hydroperoxides have been investigated, both in the liquid and solid phases. Several extremely effective ultraviolet stabilizers belonging to the metal chelate class can cause the rapid thermal decomposition of model and polymeric hydroperoxides. Although stabilizers did not reduce the quantum yield for polypropylene hydroperoxide photolysis, several additives can scavenge hydroxyl and macroalkoxy radical products which result from hydroperoxide photolytic cleavage. Ultraviolet stabilizers which were found to trap radicals were able to prevent the photodegradation of polypropylene which already contained a significant concentration of hydroperoxide groups. Highly effective polypropylene ultraviolet stabilizers probably operate by a range of mechanisms including hydroperoxide decomposition, radical scavenging and singlet oxygen quenching.

ISSN:0360-6376    

DOI:10.1002/pol.1974.170121006

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe free‐radical copolymerization of α‐methylstyrene and styrene has been studied in toluene and dimethyl phthalate solutions at 60°C. Gas chromatography was used to monitor the rate of consumption of monomers. For styrene alone, the measured rate of polymerizationRpandM̄nof the polymer coincided with values expected from previous studies by other workers. Solution viscosity η affectedRpandM̄nof styrene homopolymers and copolymers as expected on the basis of an inverse proportionality between η1/2and termination rate. The rate of initiation by azobisisobutyronitrile appears to be independent of monomer feed composition in this system. Molecular weights of copolymers can be accounted for by considering combinative termination only. The effects of radical chain transfer are not significant.A theory is proposed in which the rate of termination of copolymer radicals is derived statistically from an ideal free‐radical polymerization model. This simple theory accounts quantitatively forRpandM̄ndata reported here and for the results of other workers who have favored more complicated reaction models because of the apparent failure of simple copolymer reactivity ratios to predict polymer composition. This deficiency results from systematic losses of low molecular weight copolymer species in some analyses. Copolymer reactivity ratios derived with the assumption of a simple copolymer model and based on rates of monomer loss can be used to predictRpvalues measured in other laboratories without necessity for consideration of depropagation or penultimate unit effects. The 60°C rate constants for propagation and termination in styrene homopolymerization were taken to be 176 and 2.7 × 107mole/l.‐sec, respectively. The corresponding figures for α‐methylstyrene are 26 and 8.1 × 108mole/l.‐sec. These constants account for the sluggish copolymerization behavior of the latter monomer and the low molecular weights of its copolymers. The simple reaction scheme proposed here suggests that high molecular weight styrene–α‐methylstyrene copolymers can be produced at reasonable rates at 60°C by emulsion polymerization.

ISSN:0360-6376    

DOI:10.1002/pol.1974.170121007

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractIn order to get information on the radiolytic changes in 1,2‐polybutadiene (1,2‐PB) the sol and gel fractions, the conversion of double bonds, the structure and concentration of radicals, the formation of dienes and the formation of gaseous products were measured. In addition, the dose rate dependence and temperature dependence for the conversion of double bonds were determined.Gvalues for double bond conversion depend on molecular weight and range from 20 to 200.Gvalues for crosslinking are about 10. A mechanism for the double bond conversion is proposed which involves initiation by a transformation of the primary radical ion in the vinyl group into a carbonium ion and a radical. This is supported by ESR measurement. Reaction of the carbonium ion with a vinyl group in the same chain gives rise to cyclization, whereas reaction with a vinyl group in a neighboring chain results in crosslinking. A comparison of theGvalues for conversion of double bonds with theGvalues for crosslinking shows that the formation of cyclic rings exceeds the formation of crosslinks by a factor of about 10. The corresponding values in 1,4‐cis‐ and 1,4‐trans‐polybutadiene are much smaller [G(cl) ≃ 2;G(db) ≃ 7]. The pendent vinyl groups in 1,2‐polybutadiene therefore are more reactive than the vinylidene groups in 1

ISSN:0360-6376    

DOI:10.1002/pol.1974.170121008

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe bulk polymerization of acrylonitrile (AN) initiated by copper (II) nitrate, Cu(II), in the absence of light has been studied. The rate of the AN polymerization may be expressed in the Cu(II) concentration range from 5 × 10−4to 1 × 10−1mole 1.−1by the equation,Rp=k5[Cu(II)]0.68, wherek5=KAN[AN]/(1 +KAN[AN]). From the spectrophotometric measurements the values of 0.70 l./mole and 0.08 l, mole were obtained for the equilibrium constant at 20 and 60°C, respectively,KAN= [C]/[AN]‐[Cu(II)], corresponding to the formation of the complex C from acrylonitrile and copper (II) nitrate. An addition of triphenylphosphine (C6H5)3P into the polymerization system reducesRp, and no polymerization takes place at all provided [(C6H5)3P]/[Cu‐(II)]≧ 5. The retardation effect of (C6H5)3P on the polymerization of AN initiated by Cu(II) is attributed to a competitive reaction of Cu(II) with (C6H5)3P in which Cu(II) is reduced and the product of this reduction CuNO3·2(C6H5)3P is inactive with respect to the polym

ISSN:0360-6376    

DOI:10.1002/pol.1974.170121009

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractCellobiose and myoinositol, both as received and in physically modified form, were photolyzed at 60.0°C under vacuum with 253.7 nm light. The rates of hydrogen production were compared with the H2rate obtained from analogous photolyses of hydrocellulose. The similar physical state and optical properties of cellobiose and hydrocellulose allowed a direct comparison of H2production rates, from which it is clear that neither the glycosidic linkage, nor the number of primary or secondary hydroxyl groups, is the basis for observed differences in rates. The relative rates of H2production from myoinositol and levoglucosan indicate that strain in the pyranose ring has only a slight effect on the photolysis rate, and further, since published carbohydrate structures show that the local skeletal environment about each hydroxyl in a “defectless” unstrained carbohydrate structure is very similar in all the relevant compounds thus far determined, differences in H2rates must therefore arise as a result of possible differences in the hydrogen‐bonding environment of the hydroxyl. From an extrapolation of optical properties of simple alcohols in hydrogen‐bond‐free environments, together with a consideration of possible cage effects during photolysis, it is concluded that the precursors of the H2are hydrogen‐bond‐free hydroxyl groups of the carbohydrates. Confirmation of this hypothesis has been obtained from the H2rates observed on photolyzing cellobiose and myoinositol after these compounds had been freeze‐dried or recrystallized, which treatment results in a concentration of “defective” hydroxyls differing from the original solid, but is without effect on the overall numbers of

ISSN:0360-6376    

DOI:10.1002/pol.1974.170121010

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY