摘要:

AbstractStudies on the composition of copolymers obtained by the radiation‐induced solid‐state postpolymerization of trioxane with 1,3‐dioxolane have been carried out. Gas‐chromatographic analysis of the reaction mixtures showed that most of the 1,3‐dioxolane disappears rapidly from the reaction system in an early stage of polymerization, and that the fraction of ethylene oxide units in the copolymer chain [E] decreases markedly with increasing polymer yield. This finding was confirmed by NMR spectra of the copolymer. DSC thermograms of the copolymer indicated that the relationship between the melting point and the average composition of copolymers prepared in this study differed from that found for copolymers in which comonomer units are distributed statistically in the polymer chain. It was suggested that the copolymer formed by the radiation‐induced solid‐state postpolymerization of trioxane–1,3‐dioxolane is characterized by a heterogeneous distribution of ethylene oxide units in the copolymer chain. It was also found that, in the radiation‐induced solid‐state postpolymerization of trioxane–1,3‐dioxolane, the amount of tetraoxane formation increased linearly with increasing polymer yield. Although it is extremely small compared with that obtained in solution polymerization, it is slightly larger in the trioxane–1,3‐dioxolane syste

ISSN:0449-296X    

DOI:10.1002/pol.1972.150100701

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractPropylene oxide and tetrahydrofuran were polymerized cationically by anin situcatalytic system composed of antimony pentachloride and 1,2‐propanediol. The rates of polymerization were measured by vapor‐phase chromatography in the temperature range from −20°C to +20°C. The Arrhenius parameters pertaining to the reaction of each of the comonomers were evaluated and compared with data published earlier for other catalytic systems. The present catalyst system was incapable of initiating a homo‐polymerization of tetrahydrofuran in the absence of propylene oxide, while the latter was readily homopolymerized. In a copolymerization system, the rates of consumption of both monomers were first‐order in respect to the catalyst, but the reaction ceased when all of the propylene oxide had been consumed. The relative reactivity of the two monomers as characterized by the copolymerization parametersr1(PO) = 1.15 andr2(THF) = 0.70 suggests that in the copolymerization system, tetrahydrofuran is capable of a reaction with its own active center. This is discussed in terms of a possible mechanism involving the effects of penultimate units and extensive chain transfer. The latter is well evident from the molecular weights of resulting copolyethers, which do not exceed o

ISSN:0449-296X    

DOI:10.1002/pol.1972.150100702

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe kinetics of the solid‐state polymerization of acrylamide, γ‐irradiated at 77°K, has been studied by wide line NMR and by ESR at temperatures above 300°K. This reaction may be followed by the growth of a narrow line superimposed on the NMR spectrum of the monomer. The amplitude of this narrow line has been found to be proportional to the polymer yield. By long continued annealing, the conversion yield approaches a limiting value, generally lower than 50% under most of our experimental conditions. The activation energy of post‐polymerization is 19 ± 1 kcal/mole. The radiochemical yield of radicals, determined by ESR, is 0.27 ± 0.03 at 77°K before warming. In the course of annealing above 300°K, the overall concentration of radicals is reduced to about one tenth of its initial value at 77°K. However, the local concentration of the remaining radicals is constant and equal to 1.2 × 1019spins/g, i.e., more than 100 times their overall concentration. The recombination of radicals does not seem to intervene in the kinetics of post‐polymerization, so that it may be assumed that only the radicals remaining after annealing, have actually contributed

ISSN:0449-296X    

DOI:10.1002/pol.1972.150100703

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe post‐polymerization of acrylic acid, γ‐irradiated at 77°K, has been studied by broad‐line NMR and ESR between 240°K and 286°K (mp). The changes in the structure of NMR spectra during the polymerization has been related to the conversion yield checked by gravimetry of the polymer formed. The very fast reaction occurring above ⋍270°K has been followed simultaneously by NMR and thermal analysis. This last method indicates an activation energy of chain propagation of 18.6 ± 2 kcal/mole in satisfactory agreement with the value given by the initial slope of the conversion—time curves. ESR experiments show that, while the average radical concentration decays by a factor of about ten between 77°K and 240°K, the local concentration of radicals persisting after prolonged annealing atT>240°K, remains the same as at 77°K, i.e., 1.4 × 1019spins/g. A kinetic scheme, assuming an exponential decay of propagation and termination rate constants with chain length, has been proposed to explain the shape of conversion—time curves as well as the almost constancy of the local concentration of

ISSN:0449-296X    

DOI:10.1002/pol.1972.150100704

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractEPR studies were carried out on different irradiated cellulosic materials. The shape of the EPR spectrum was found to depend upon the fine structure of cellulose. The peak‐to‐peak distances of the large peaks on the differential curves were found to be 23.3 and 24.8 gauss, respectively, for the amorphous and recrystallized cellulose. The number of free radicals present per unit weight in the recrystallized cellulose and in the amorphous cellulose were found to be in the ratio of 2.1:1. The EPR spectrum of a sample of irradiated cotton crystallites which was soaked in acetone before being dried was markedly symmetrical, in contrast to the EPR spectra of samples of cotton linters and of cotton crystallites dried from water, and was considered to be a reflection of the lower intermolecular bonding in the former. For corresponding doses, the free radicals on cotton crystallites have the highestgvalue, followed by cotton linters, followed by regenerated cellulose I. Thegvalue decreased as the irradiation dose was increa

ISSN:0449-296X    

DOI:10.1002/pol.1972.150100705

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractHigh molecular weight, 1:1 alternating copolymers of 1‐bicyclobutanecarbonitrile with styrene were prepared in tetramethylenesulfone solution by complexing the electron‐poor bicyclobutane monomer with zinc chloride. Methyl 1‐bicyclobutanecarboxylate under these conditions gave copolymers containing a slight excess of styrene units (ratio 1:1.3 to 1:1.8). High molecular weight homopolymers of 1‐bicyclobutanecarbonitrile and of methyl 1‐bicyclobutanecarboxylate were prepared similarly. The tendency of the bicyclobutane nitrile to form 1:1 alternating copolymers is as great as that of its vinyl analog, acrylonitrile, and the synthesis of other alternating copolymers from this monomer should be

ISSN:0449-296X    

DOI:10.1002/pol.1972.150100706

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe silver complexes of various thiols of low molecular weight have been studied by amperometric and spectrophotometric titrations. Cysteine and cysteamine form complexes with silver containing up to 1.5 Ag+/—SH. The ligands participating in the binding of silver are the —SH and amino groups.Under some conditions it was found that 1:1 thiol‐silver polymers were formed. These polymers probably have the general structure AgS(R)AgS(R). Some of them were prepared in pure form and subjected to various studies. Molecular weight determinations of the cysteine‐silver and glutathione‐silver polymers yielded values of 4000–7000 daltons. Studies on the UV absorption characteristics revealed that all of the polymers showed some type of regular band pattern. The cysteamine‐silver polymer is able to sensitize

ISSN:0449-296X    

DOI:10.1002/pol.1972.150100707

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

Abstractm‐Aminophenol was condensed with formaldehyde in an acid medium in the presence of a water‐soluble inorganic salt (NaCl, CaCl2etc) and/or poly(ethylene glycol). The pore structure characteristics of the condensation products were investigated by measurements of average pore size, pore size distribution of channels, total pore volume, surface area, and electron microscopic observation. The type and concentration of inorganic salts appeared to be a significant variable for the resulting pore structure, while poly(ethylene glycol) had a little effect. The nongel interstices of products were channels between many agglomerates of minute spherical gel particles with narrow pore size distribution. The diameters of these spherical gel particles were 3–10 × 10−1µ from the scanning electron microscopic observation. Apparent dissociation constants of functional groups of resin, pKaand pKb, estimated by using the Henderson‐Hasselbach equation, were 10.94 and 10.99, respectively. The resin had an ion‐exchange capacity of 1.0 meq/g for base and 4.8 m

ISSN:0449-296X    

DOI:10.1002/pol.1972.150100708

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractSynthesis and reactions of 4‐carboxy‐6‐alkyl‐2‐piperidones and 4‐carboxyl‐6‐alkyl‐2‐pyrrolidones are described. Upon heating, the substituted 4‐carboxy‐2‐piperidones underwent both polymerization to polysuccinimides and isomerization to pyrrolidone derivatives. No polymerization but isomerization to ethylidene succinimide was observed upon heating the substituted 4‐carboxy‐2‐pyrrolidone. Both polymerization and isomerization can be explained by

ISSN:0449-296X    

DOI:10.1002/pol.1972.150100709

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractMixtures of sulphur dioxide and butene‐1 have been polymerized in the gas phase to the 1:1 alternating copolymer by electron irradiation. The rate of polymerization, measured by the decrease in gas pressure,decreasedwith increase in temperature over the range −20 to +30°C. The initial G(‐monomer) values decreased from 500 to 50 giving an Arrhenius activation energy of −30 kJ mol−1. These results are consistent with a ceiling temperature‐pressure relationship. The ceiling temperature is about 60°C lower than that observed previously in the liquid phase in accord with thermo‐dyn

ISSN:0449-296X    

DOI:10.1002/pol.1972.150100710

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY