bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessment of the state of order of hydroxyl groups and of molecular segments in hydrocellulose
Authors: Rowland S. P. , Roberts E. J. , Bose J. L. , Wade C. P. 
Published: April 2003

AbstractThrough a study of the selective distribution of substituents introduced into hydrocellulose from reaction with N,N‐diethylaziridinium chloride, the change in selective availability of hydroxy groups at C‐2, C‐3, and C‐6 has been followed as a function of duration of hydrolysis to form the hydrocellulose. The hydrocellulose formed at a particular duration of hydrolysis showed maximum selective availability of hydroxyl groups; this was found to coincide with minimum moisture regain and minimum breadth at half height for 101, 101, and 002 peaks in x‐ray diffractograms. These points are discussed in terms of the structures of the hydrocelluloses at various stages of hydrolysis and in terms of the sequence of changes which is now associated with the conversion of fibrous cotton to “exemplar hydrocellulose,” i.e., the hydrocellulose having the highest degree of crystalline order, and subsequently, to less highly ordered hydrocelluloses.
Thermal decomposition of poly(vinyl chloride) and chlorinated poly(vinyl chloride). I. ESR and TGA studies
Authors: Liebman S. A. , Reuwer J. F. , Gollatz K. A. , Nauman C. D. 
Published: April 2003

AbstractSignificant effort has been made in the past by many workers to investigate the mechanism of thermal decomposition of poly(vinyl chloride) (PVC). The presence and role of free radicals has been controversial in this regard. Our data on PVC and chlorinated PVC systems demonstrate the existence of macroradicals in the early stage of thermal decomposition under inert and oxidative atmospheres. Data from conventional thermogravimetric experiments are used in conjunction with the electron spin resonance findings.
Radiation‐initiated homogeneous grafting of styrene to benzylcellulose
Authors: Betty R. W. , Rapson W. H. 
Published: April 2003

AbstractGraft copolymers of benzylcellulose and styrene were prepared by direct irradiation of benzylcellulose–styrene solutions with 60Co γ‐radiation. The solutions remained homogeneous during irradiation. The amount of styrene grafted to benzylcellulose increased in dilute solutions and was dose‐dependent up to 4.0 MR. The graft copolymer consisted of both branched and linear structures with one in every 140–1020 benzylated anhydroglucose units carrying a grafted polystyrene chain. Grafted polystyrene was isolated from the graft copolymer by hydrolysis of the benzylcellulose substrate. The number‐average molecular weight and molecular weight distribution of the grafted polystyrene were the same as those for hompolymer formed in the same solution, indicating that the substrate is fully accessible to the monomer and polymerization conditions are uniform throughout the solution during the grafting procedure. The existence of a true graft copolymer was proved by the solubility behavior, intrinsic viscosity, number‐average molecular weight, and density‐gradient sedimentation of the product of the grafting procedure. Column elution fractionation of the gross products of the grafting procedure failed to isolate the benzylcellulose–styrene copolymer which was eluted with ungrafted benzylcellulose.
Thermal decomposition of poly(vinyl chloride) and chlorinated poly(vinyl chloride). II. Organic analysis
Authors: Liebman S. A. , Ahlstrom D. H. , Quinn E. J. , Geigley A. G. , Meluskey J. T. 
Published: April 2003

AbstractA concerted study of poly(vinyl chloride), chlorinated poly(vinyl chloride), and poly(vinylidene chloride) polymers by spectroscopy, thermal analysis, and pyrolysis‐gas chromatography resulted in a proposed mechanism for their thermal degradation. Polymer structure with respect to total chlorine content and position was determined, and the influence of these polymer units on certain of the decomposition parameters is presented. Distinguishing differences were obtained for the kinetics of decomposition, reactive macroradical intermediates, and pyrolysis product distributions for these systems. It was determined that chlorinated poly(vinyl chloride) systems with long‐chain CHCI units were more thermally stable than the unchlorinated precursor, exhibited increasing activation energy for the dehydrochlorination, and produced chlorine‐containing macroradical intermediates and chlorinated aromatic pyrolysis products. The poly(vinyl chloride) polymer was relatively less thermally stable, exhibited decreasing activation energy during dehydrochlorination, and produced polyenyl macro‐radical intermediates and aromatic pyrolysis products.
Thermal and photochemical oxidation of 2,6‐dimethylphenyl phenyl ether: A model for poly(2,6‐dimethyl‐1,4‐phenylene oxide)
Authors: Jerussi Robert A. 
Published: April 2003

AbstractThe oxygenation of 2,6‐dimethylphenyl phenyl ether (I) at 260°C has resulted in the formation of 4‐methylxanthone (II), 2‐hydroxy‐3‐methylbenzophenone(III), 2‐phenoxy‐3‐methylbenzaldehyde (IV), 2‐phenoxy‐3‐methylbenzoic acid (V), 2‐phenoxy‐3‐methylbenzyl o‐cresotinate (VI), 2‐phenoxy‐3‐methylbenzyl alcohol (VII), and 2‐phenoxy‐3‐methylbenzyl 2‐phenoxy‐3‐methylbenzoate (VIII), The photochemical oxidation at 75° produced compounds II, III, IV, VII, and VIII. Oxidation of poly(2,6‐dimethyl 1,4‐phenylene oxide) film at 200°C and photochemically at 50°C produced a carbonyl band at ca. 1730 cm−1. The gel content of the photochemically aged film could be significantly reduced and the 1730 cm−1 peak in the thermally aged specimen could be moved to longer wavelength by base treatment. The isolation of compound VIII in both processes with the model compound and the results with the polymer allows us to propose an ester group as a crosslinking unit in thermally and photochemically aged polymer film.
Polymerization of methyl methacrylate under ultrasonic irradiation. Part V. Effect of ultrasonic irradiation on stereoregularity of the polymers and oligomers produced by grignard catalyst in toluene–dioxane mixed solvent
Authors: Osawa Zenjiro , Kimura Takao , Ogiwara Yoshitaka , Matsubayashi Noriyuki 
Published: April 2003

AbstractPolymerization of methyl methacrylate with Grignard reagent in toluene–dioxane mixed solvent was carried out under ultrasonic irradiation. The effects of ultrasonic irradiation and the order of catalyst addition on Grignard reagent and the microstructure in the reacting sites were examined on the basis of the stereoregularity of polymers and oligomers produced. The formation of oligomers was also discussed on the basis of the consumption of initiator. The stereoregularity of the polymers in series A (no ripening of catalyst with solvent) is higher than that in series B (ripening of catalyst with solvent). The effect of ultrasonic irradiation on the stereoregularity was completely reversed in series A and B; it increased in the former and decreased in the latter with ultrasonic irradiation. Similar results were obtained for the stereoregularity of the oligomers, but the stereoregularity of the oligomers was lower than that of polymers.
Effect of crystallinity on radiation‐induced graft copolymerization on cellulose
Authors: Ahmed A. U. , Rapson W. H. 
Published: April 2003

AbstractWith vinyl monomers, viz., styrene, butyl methacrylate, dimethylaminoethyl methacrylate, and ethyl acrylate, it was noted that higher per cent grafting was obtained with “recrystallized” cellulose than with “amorphous” cellulose. The possibility of the production of a porous structure in cellulose as a result of γ‐irradiation followed by the dissolution of the reactive regions is suggested. DTA and DTG data of irradiated cellulose triacetate (CTA) reveal lowering of the melting point on irradiation, indicating a decrease in crystallinity. Decrease in density of cellulose on irradiation by γ‐rays also indicates loosening of the structure of cellulose. It is postulated that grafting occurs in those regions of cellulose which were crystalline before irradiation, as well as in less crystallinie regions.
Telechelic diene prepolymers. II. Carboxyl‐terminated polydienes
Authors: Reed Samuel F. 
Published: April 2003

AbstractButadiene, isoprene, and chloroprene have been polymerized in dioxane under free‐radical initiation to give liquid prepolymers containing terminal carboxyl groups. 4,4′‐Azobis(4‐cyanovaleric acid) was employed as the initiator. The prepolymers were obtained with molecular weights of 12,000 to 2000 and with functionalities usually greater than 2.0. Experimental parameters were studied to determine their effect on prepolymer yields and properties. The general preparative procedure and prepolymer characterization are described.
On the condensation equilibrium in polymerization of caprolactam
Authors: Reimschuessel H. K. , Dege G. J. 
Published: April 2003

AbstractThe investigation of the condensation equilibrium of the hydrolytic polymerization is described for systems obtained by polymerizing caprolactam in the presence of water (or aminocaproic acid) and any of the following additives: mono‐ di‐, and tricarboxylic acids, mono‐ and diamines, and the salts derived from a monoamine and either a mono‐ or dicarboxylic acid. Relationships in terms of the equilibrium constant K2, the equilibrium conversion (K3), and the initial composition were derived for the calculation of the molecular weights of the corresponding equilibrium polymers. Very good agreement between calculated and experimental data was observed. The results show that the thermodynamical quantities derived for the pure caprolactam–water system are also valid for polymerizations that involve the participation of organic acids, amines, and their salts in the initiation and equilibration.
Polymerization of propadiene. I. Comparison of catalytic systems in relation to polymer structure and polymerization by a new Ni‐based catalyst
Authors: Van Den Enk J. E. , Van Der Ploeg H. J. 
Published: April 2003

AbstractA literature survey is given of the methods of preparation of 1,2‐and 1,2,2,1‐polyallene. The spectroscopic data and other physico‐chemical properties are compiled. Spectral analysis of the products in relation to the catalyst used leads to conclusions with regard to the effect of electron‐donating and electron‐withdrawing ligands to the transition metal of the catalyst on the ratio of 1,2 to 1,2,2,1‐polyallene structural units in the polymer obtained. This hypothesis enabled us to prepare a structurally homogeneous 1,2 polyallene in almost quantitative yield. The catalyst was prepared by adding propadiene to a benzene solution of Ni(II) acetylacetonate followed by addition of triisobutylaluminum. This sequence of addition appeared to be the essential factor for obtaining an active catalyst. A kinetic scheme for the polymerization is put forward.
Radiation‐induced postpolymerization of trioxane in the solid state. III. Effect of oxygen on the postpolymerization of trioxane
Authors: Ishigaki Isao , Ito Akihiko , Iwai Tadashi , Hayashi Koichiro 
Published: April 2003

AbstractIn order to investigate the effects of oxygen on the radiation‐induced postpolymerization of trioxane in the solid state, a kinetic study has been made. Trioxane was purified by sublimation through Ag2O and Na‐K alloy in vacuo and was irradiated and polymerized in the presence of rigorously dry oxygen. It was found that the initial rate of polymerization and the polymer yields are larger than those obtained in vacuo. By using the kinetic scheme proposed previously the results were analyzed kinetically. It was found that the influence of oxygen on the postpolymerization of trioxane is mainly attributable to the increase in the concentration of active species. The results obtained in dry air have been discussed in comparison with those in vacuo reported previously.
Vacuum and oxidative pyrolysis of poly‐p‐xylylene. II. Chromatographic analysis and kinetics of reaction products
Authors: Jelinek H. H. G. , Ronel S. H. 
Published: April 2003

AbstractReaction products of vacuum and oxidative degradation of poly‐p‐xylylene have been quantitatively determined by chromatographic analysis as function of time, temperature and oxygen pressure. Respective Arrhenius parameters were also ascertained for some of the reaction products and for the sums of all products. The energies of activation for the sums agree quite satisfactorily with the energies of activation obtained previously by uninterrupted experiments in quartz‐spoon reaction vessels. The results found here can be described in terms of mechanisms previously postulated on the basis of the total loss in weight (or volatile production) data. Scission of “weak” links (due to abnormal structures) takes place followed by formation of various products. The whole process is governed by the initial chain scission reaction; however, the energies of activation for each of the products do not need to be identical with that of the chain scission reaction. Each product is formed by a reaction which has its own characteristic number average kinetic chain lengths; the latter have their specific energy of activation values.Oxidative degradation produces the same organic compounds as vacuum degradation and in addition CO, CO2, and H2O. Oxidized intermediate compounds are apparently fairly rapidly decarboxylated and decarbonylated. Oxidative chain scission is appreciably faster than that in vacuum. Almost simultaneous “weak” link and “normal” chain scission are taking place initiating the formation of a number of products.
Antioxidative stabilization of poly(vinyl chloride)
Authors: Stapfer Christian H. , Granick Joel D. 
Published: April 2003

AbstractHalogenated resins such as poly(vinyl)chloride undergo rapid degradation when exposed to heat. Such degradation is significantly increased by oxygen, and it is believed that the induction of the process of decomposition is caused by autoxidation of the polymer, followed by extensive dehydrohalogenation. Sulfur‐containing peroxide decomposers allow primary stabilization of PVC with organic compounds which are not HCl acceptors but prevent free radical cross‐linking of the polymer. This implies a discolored polymer melt (due to loss of HCl and formation of polyenes) which nonetheless exhibits good long term stability (no cross‐linking). The stabilization of labile chlorine atoms results from the oxidation of various chain irregularities, and thus the elimination of the early discoloration can be achieved by the use of small quantities of monohydrocarbyltin co‐stabilizers. The relative performance of various antioxidant systems are reported and possible stabilization mechanisms are discussed.
Formation and reactions of radiation‐induced free radicals in chemically modified cotton celluloses
Authors: Chidambareswaran P. K. , Sundaram V. , Prakash Jai , Verma N. C. , Singh B. B. 
Published: April 2003

AbstractWith a view to assessing the role of chemical substitutions in the modification of radiation effects on cotton fibers, the induction and post‐irradiation behavior of free radicals in γ‐irradiated pure, mercerized, benzoylated, and allylated cottons have been investigated by ESR spectroscopy. While mercerization and allylation were found to influence both the nature and yield of radicals, benzoylation reduced only the yield. These substitutions, which have been found to protect cotton fibers against radiation damage, therefore act differently at the molecular level.
Friedel‐crafts copolymerization of thiophene and p‐di(chloromethyl)benzene. I. Products, kinetics, and mechanism of the early stages of the reaction
Authors: Grassie N. , Colford J. B. , Meldrum I. G. 
Published: April 2003

AbstractThe rate of polymerization of thiophene, at concentrations of catalyst (SnCl4), and thiophene of the same order as was subsequently used in studying the reaction between thiophene and di(chloromethyl)benzene, is of the order of 10‐2%/hr at 30°C. There is no significant self‐condensation of DCMB under the same conditions. Since the reaction between thiophene and DCMB is complete at 30°C in minutes rather than hours, it is assumed that self‐condensation of thiophene or DCMB during the reaction between them will be negligible and should not influence the course of the reaction or the structure of the resulting polymer. Reaction at 30°C is much too fast for convenient study. A temperature of 0°C is more appropriate and was used in subsequent kinetic work. The first two products of the condensation of p‐di(chloromethyl)benzene (DCMB) with thiophene have been identified by a combination of mass, infrared, and nuclear magnetic resonance spectroscopy as thenylchloromethylbenzene (TCMB) and dithenylbenzene (DTB). DCMB, TCMB, and DTB have been estimated quantitatively during the course of the reaction by gas‐liquid chromatography (GLC), and it has been established that the rates of each of the two reaction steps is first‐order with respect to the chloro compound (DCMB and TCMB respectively), thiophene, and SnCl4. Rate constants for these two consecutive reactions were calculated to be k1 = 2.79 × 10‐4l.2/mole2‐sec, k2 = 6.37 × 10‐3l.2/mole2‐sec; the corresponding energies of activation are E1 = 7.93 kcal/mole, E2 = 7°67 kcal/mole. These rate constants are appreciably higher than values previously obtained for the corresponding DCMB–benzene reactions.
Studies with inorganic precipitate membranes. III. Consideration of energetics of electrolyte permeation through membranes
Authors: Siddiqi Fasih A. , Lakshminarayanaiah N. , Beg Mohammad N. 
Published: April 2003

AbstractThe permeability of various electrolytes through parchment‐supported ferrocyanide membranes of manganese, cobalt, silver, and cadmium has been measured at 10, 15, 20, 25, and 30°C. The order of permeability at a given temperature was Cl‐ > NO3‐ > CNS‐ > CH3COO‐ > SO42‐ for both monovalent and divalent cations. For any given anion, the cations followed the sequence NH4+ > Li+ > Ba2+ > Ca2+ > Mg2+ > Al3+. This sequence has been correlated with the size of the hydrated ion. Further, the data have been considered from the standpoint of the theory of rate processes and the values for the entropy of activation (ΔS′) have been derived assuming an equilibrium distance of 3 Å in the membrane. The values of ΔS′ were all negative and decreased with increasing valence of the ions. This was interpreted to mean electrolyte permeation with partial immobilization in the membrane.
Radical copolymerizations of β‐propiolactone with acrylonitrile and with styrene
Authors: Katayama Shitomi , Horikawa Hideichi , Toshima Osamu 
Published: April 2003

AbstractRadical copolymerizations of β‐propiolactone (denoted 2) with acrylonitrile (denoted 1) and with styrene (also denoted 1) and the structures of the resulting copolymers were studied. The bulk copolymerization with acrylonitrile by α,α′‐azobisisobutyronitrile at 50°C gave polyesteracrylonitriles of high enough molecular weight to form tough and transparent films, with the monomer reactivity ratios, r1 = 0.84, r2 = 0.00, and the structure of the copolymers was
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Radical copolymerization with the same initiator in N,N‐dimethylformamide gave polyesteracrylonitriles of the same structure as that of the bulk polymer, blended with β‐propiolactone homopolymer which was due to the competing anionic homopolymerization of β‐propiolactone. The reactivity ratios on the bulk copolymerization with styrene were r1 = 6.2 and r2 = 0.0 with benzoyl peroxide at 80°C, and r1 ≅ 32, r2 = 0 with α,α′‐azobisisobutyronitrile at 50°C. Polyesterstyrenes of intrinsic viscosity up to 0.83 were obtained.
Synthesis of 1,2‐bis(4‐aminocyclohexyl)ethane and its polyamides
Authors: Komoto Hiroshi , Hayano Fusakazu , Takami Toshio , Yamato Sadao 
Published: April 2003

AbstractThe synthetic route to 1,2‐bis(4‐aminocyclohexyl)ethane from toluene via p‐nitrotoluene and p,p′‐dinitrodibenzyl was established. The distribution of geometric isomers was estimated by NMR and fractional recrystallization. Polyamides were synthesized from 1,2‐bis(4‐aminocyclohexyl)ethane and dodecanedioic or sebacic acid. Polymer melting temperatures were varied with isomer compositions. A high content of the trans conformation causes high melting temperatures. Glass transition temperatures of polyamides were in the range of 105–120°C and were less sensitive to isomer compositions.
Polymers containing anthraquinone units: Polymers from 1,5‐diaminoanthraquinone and aralkyldiketones
Authors: Mortier Roy M. , Dutt P. K. , Hoefnagels J. , Marvel C. S. 
Published: April 2003

AbstractSchiff's‐base polymers have been formed by the condensation of 1,5‐diaminoanthraquinone with 1,4‐ and 1,3‐diacetylbenzene and 2,6‐diacetylpyridine. These polymers were soluble in methanesulfonic and concentrated sulfuric acids (1,4‐diacetylbenzene polymer) or N,N‐dimethylacetamide. The polymer formed from 1,4‐diacetylbenzene was ring‐closed in polyphosphoric acid to yield a thermally stable polymer soluble in concentrated sulfuric acid which lost only 10% of its weight at 900°C in a TGA test.
Optical rotatory properties of synthetic polymers. I. Optical inversion of poly(propylene oxide)
Authors: Tsunetsugu Toshiyuki , Furukawa Junji , Fueno Takayuki 
Published: April 2003

Abstract(+)‐1,2‐Diethoxypropane, a model diether for the repeating unit of poly(propylene oxide), was prepared, and its behavior in solutions regarding optical rotatory dispersion and proton magnetic resonance was compared with those of the polymer. It was found that the model compound and the poly(propylene oxide) show essentially the same optical properties in solutions. By using the Brewster model of optical activity, it was concluded that the solvation of the polymer may well modify the polarizability of the optically active species to cause changes in the order of the polarizabilities of four atoms directly attached to the asymmetric carbon atom. The explanation is shown to be applicable also to some of related polymers.
Kinetic aspects of the copolymerization of tetrahydrofuran with alkylene oxides
Authors: Blanchard L.‐P. , Kondo S. , Moinard J. , Pierson J. F. , Tahiani F. 
Published: April 2003

AbstractCationic (BF3) copolymerizations and terpolymerizations of 1,2‐butylene oxide (BO), propylene oxide (PO), and tetrahydrofuran (THF), have been carried out at 0°C in ethylene dichloride under dry inert conditions. Reactivity ratios of THF–BO, THF–PO and BO–PO systems have been determined with the use successively of 1,2‐propanediol and 1,2,3‐propanetriol (glycerine) as cocatalysts. Terpolymer compositions established experimentally compare well with those predicted by calculations with the reactivity rations determined in the binary systems. With the triol as cocatalyst, the existence of a ternary azeotrope was confirmed. Its composition is: M1(THF) = 0.125; M2(BO) = 0.205; and M2(PO) = 0.670.
Kinetic aspects of catalyzed reactions in the formation of poly(ethylene terephthalate)
Authors: Hovenkamp S. G. 
Published: April 2003

AbstractThe influence of different types of catalysts on the polycondensation reaction has been studied in a model system. It has been found that two kinds of catalysts are to be distinguished. “Transesterification” catalysts (Mn, Pb, Zn) are very active in media having both a high and a low hydroxyl content. However, they are easily poisoned by very small amounts of carboxylic endgroups. This restricts their activity to the period of transesterification. The “polycondensation” catalyst antimony is insensitive to the presence of acidic endgroups. However, its activity is inversely proportional to the hydroxyl group concentration For this reason antimony is hardly effective during transesterification. During polycondensation it becomes gradually more active.