bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some aspects of graft polymerization of vinyl monomers onto cellulose with the use of tetravalent cerium. V
Authors: Mansour O. Y. , Nagaty A. 
Published: April 2003

AbstractThe presence of occluded air lowers the ceric consumption between the beginning and end of the reaction time, decreases the grafting parameters, and increases the copper number. Grafting reactions carried out in presence of organic solvents show parameters that are lower than those obtained when the reactions are carried out in water. Solvents with high chain‐transfer constants cause a marked decrease in the yield relative to the solvents of low chain‐transfer constants. Conversion percentages are similarly influenced. However, the donor alcohols enhance polymer formation with the acceptor monomers; this is attributed to the ability of ceric salt solution to oxidize alcohol and hence initiate polymerization reaction. Scavenging of the free radicals by certain alcohols and competition between alcohol and cellulose for the ceric consumption are responsible for the low grafting yields achieved. The order of reactivity of monomers may change when solvents are used; it follows the relative differences in the chaintransfer constant of solvent with the different monomers. Pseudografting and complex formation, when they occur, interfere with the results achieved.
The macroester ⇄ macroion equilibrium in the cationic polymerization of THF observed directly by 300 MHz1 H NMR
Authors: Matyjaszewski Krzysztof , Penczek Stanisłw 
Published: April 2003

AbstractTwo isomeric forms of active chain ends were observed simultaneously in the living cationic polymerization of tetrahydrofuran (THF) initiated with derivatives of trifluoromethanesulphonic acid (CF3SO2OH). These forms are
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the macroion and the macroester. Concentrations of both species were determined in the polymerization of THF conducted in CCl4, CH2Cl2, and CH3NO2, by using 300 MHz 1H NMR spectroscopy. In CCl4 the macroester form dominates (96%), and in CH3NO2 only 8% of macroester could be detected. In CH2Cl2 both species coexist in comparable concentrations ([macroion]:[macroester] = 1:3). The present direct measurements are in agreement with our previous determination of the proportions of macroester and macroions based on kinetics data. Therefore, this also confirms our earlier conclusion, that if an equilibrium between the macroions and macroester is involved in the polymerization of THF, the chain growth proceeds almost exclusively on the macroions.
Aromatic polyethers, polysulfones, and polyketones as laminating resins. III
Authors: Sivaramakrishnan K. P. , Marvel C. S. 
Published: April 2003

Abstract4,4′‐Diphenoxydiphenylsulfone was polymerized with isophthaloyl chloride and terephthaloyl chloride in Friedel‐Crafts polymerizations. These polymers had 5‐cyanoisophthaloyl units in the backbone obtained either by using 1,3‐bis(p‐phenoxybenzoyl)‐5‐cyanobenzene or 5‐cyanoisophthaloyl chloride as part of the acid chloride monomer. A terpolymer having 22 wt‐% 5‐cyanoisophthaloyl unit was also prepared from the Friedel‐Crafts polymerization of 1,3‐bis(p‐phenoxybenzenesulfonyl)benzene and 5‐cyanoisophthaloyl chloride. These terpolymers were crosslinked through heating to give insoluble products which proved to be thermally less stable than the uncrosslinked polymers.
Preparation of a polypentenamer having pendant ionic groups and its hydrogenated derivatives
Authors: Sanui K. , Lenz R. W. , MacKnight W. J. 
Published: April 2003

AbstractPolypentenamers having pendant carboxylate groups including esters, acids, and salts and their hydrogenated derivatives have been prepared and characterized, and some of their properties investigated. Reaction conditions were established to control the amount of pendant thioglycolate groups incorporated into the polypentenamer by the free‐radical addition reactions of thioglycolic acid derivatives and subsequently to completely hydrogenate the polymers so formed, which contained thioglycolate contents ranging from less than 1 mole‐% to about 16 mole‐%, without backbone degradation and crosslinking reactions. The glass transition temperatures and the melting points of these polymers were observed to depend upon the pendant group content, as expected, but there appears to be little difference within these properties between polymers in which the pendant groups were in the salt form as compared to those of the corresponding carboxylic acid form. The thermal stabilities of the polymers having the pendant groups were somewhat lower than those of the parent polymers, apparently because of side reactions involving the thioglycolate groups. The calcium salt derivative showed a particularly low thermal stability compared to that of polymers with monovalent salts.
Phenolic resins for solid‐phase peptide synthesis: Copolymerization of styrene and p‐acetoxystyrene
Authors: Arshady R. , Kenner G. W. , Ledwith A. 
Published: April 2003

AbstractDetails are given of the synthesis and purification of p‐acetoxystyrene and its solution and suspension copolymerization with styrene. Reactivity ratios, evaluated by the Tidwell‐Mortimer method, were r1 (p‐acetoxystyrene) = 1.18, and r2 (styrene) = 0.88 for (bulk) solution copolymerization. Corresponding values of the reactivity ratios for suspension copolymerization were, within experimental error, indistinguishable from unity. Thus the copolymer composition is governed simply by the monomer feed composition. Use of a specially designed reactor vessel permits convenient suspension copolymerization of styrene, p‐acetoxystyrene, and divinylbenzene to give crosslinked resins having comparatively narrow particle size distributions. Acetoxy groups in the crosslinked resin are cleaved by hydrazine hydrate under very mild conditions to give crosslinked polystyrenes having phenolic groups which, in turn, provide a useful alternative to the more usual chloromethylated polystyrene resins for solid‐phase peptide synthesis.
Role of chain transfer in heterogeneous polymerization of ethylene
Authors: Watanabe Terutaka , Wada Takeshi , Takehisa Masaaki , Machi Sueo 
Published: April 2003

AbstractThe role of chain transfer was studied for the radiation‐induced polymerization of ethylene in precipitating media, namely n‐butyl alcohol, tert‐butyl alcohol and their mixtures. The affinities of those solvents for polyethylene are similar, but the chain‐transfer coefficient of n‐butyl alcohol is larger than that of tert‐butyl alcohol. The polymerizations were carried out in a reactor of 100 ml under a pressure of 300 kg/cm2, at 60°C, dose rate of 3.07 × 104–1.75 × 105 rad/hr in the presence of 50 ml of solvents. The polymerization in tert‐butyl alcohol shows the kinetic behavior characteristic of a heterogeneous polymerization, such as rate acceleration, high dose rate dependence of polymerization rate, and low dose rate dependence of polymer molecular weight, whereas the polymerization in n‐butyl alcohol does not exhibit such behavior and gives polymer having a molecular weight much lower than that of polymer obtained in tert‐butyl alcohol. The polymer formed in tert‐butyl alcohol exhibits a bimodal molecular weight distribution measured by gel permeation chromatography. In mixed tert‐butyl alcohol and n‐butyl alcohol solvent, with increasing fraction of n‐butyl alcohol, the two peaks not only shift to lower molecular weight but the higher molecular weight peak becomes relatively small. Eventually, the polymer formed in n‐butyl alcohol exhibits a unimodal distribution. Those results are well explained on the basis of the proposed scheme for heterogeneous polymerization.
Dynamic mechanical studies of endgroup‐modified polystyrene
Authors: Fellers J. F. , Rahbar‐Semanani M. 
Published: April 2003

AbstractPolystyrenes having both modified and unmodified endgroup structures were synthesized. These polystyrenes were then subjected to dynamic mechanical testing below their glass transition temperature. The modified structures were shown to influence the β transition of polystyrene. While the mechanism of this secondary transition has been speculated but never unequivocally substantiated in the past, the evidence presented here strongly support the idea that the β transition of polystyrene arises from chain‐end motions.
Influence of fine structure on the pyrolysis of cellulose. III. The influence of orientation
Authors: Basch A. , Lewin M. 
Published: April 2003

AbstractThe effects of orientation upon the pyrolysis of cellulose were investigated by using a series of rayon fibers which differed only in orientation. The initial weight loss seen in low‐temperature vacuum pyrolysis is due to crosslinking in the less ordered regions and was shown to be a first‐order reaction whose rate varies directly with the degree of orientation. The extent of this reaction decreases with increasing orientation and is directly related to the amount of char formed at higher temperatures. The bulk pyrolysis rate increases with increasing orientation. DSC, air pyrolysis rates, and levoglucosan formation were also studied.
Effect of neighboring groups in macromolecular reactions: Distribution of units
Authors: Platé N. A. , Litmanovich A. D. , Noah O. V. , Toom A. L. , Vasilyev N. B. 
Published: April 2003

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.
Photolysis of cellulose and related compounds by 253.7 nm light. II. The role of defects in hydrogen production
Authors: Bos A. 
Published: April 2003

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 H2 rate obtained from analogous photolyses of hydrocellulose. The similar physical state and optical properties of cellobiose and hydrocellulose allowed a direct comparison of H2 production 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 H2 production 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 H2 rates 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 H2 are hydrogen‐bond‐free hydroxyl groups of the carbohydrates. Confirmation of this hypothesis has been obtained from the H2 rates 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 “ordinary” hydroxyls.
Transformations of polymers and copolymers of acrylonitrile during heterogeneous saponification
Authors: Geller A. A. , Yereshchenko A. G. , Zgibneva Zh. A. , Polovnikova M. V. 
Published: April 2003

AbstractThe kinetic and thermodynamic specific features of the process of heterogeneous alkaline saponification of the copolymer of acrylonitrile (92.2%), methyl acrylate (6.3%), and sodium monoithaconate (1.5%) were investigated. Chemical and infrared spectroscopic methods reveal that the saponification of the nitrile groups of copolymer of acrylonitrile proceeds faster to yield amide groups and then slower to yield carboxylate groups. The order of both stages of the process with respect to the accumulation of the respective groups was evaluated. The dependence of the rate of saponification on the packing density of the structural units was demonstrated. With increasing conversion, the fiber structure becomes looser, as demonstrated by density and sorption investigations. If acrylonitrile copolymer is treated with alkali, the carboxylate groups in the polymer substrate accumulate as a result of saponification of the ester groups of the copolymer, while the nitrile groups are predominantly transformed into the amide groups. If the degree of conversion (with respect to the CN groups) is higher than 62.7%, the copolymer abruptly suffers a marked change in its mechanical properties and gradually dissolves. The products of partial saponification of copolymer were investigated by thermomechanical methods and DTA. The polycyclization of the polymer substrate was found to proceed at a temperatures which decreases as the content of the amide groups increases.
Synthesis and properties of phosphorus–containing polycarbonates
Authors: Hashimoto Shizunobu , Furukawa Isao , Kondo Teruhiko 
Published: April 2003

AbstractAromatic polycarbonates were prepared from several dichloroformates with phosphorus‐containing bisphenols, such as bis(p‐hydroxyphenyl)methyl phosphine oxide and bis(p‐hydroxyphenyl)phenyl phosphine oxide, or with nonphosphorus bisphenols by interfacial, low‐temperature solution, and high‐temperature solution polycondensation. The interfacial polycondensation gave the best results for polycarbonates, from which colorless, transparent, and fairly though films were cast. In contrast to analogous nonphosphorus polycarbonates, the phosphorus‐containing polycarbonates exhibited lower polymer melt temperatures, greater range of solubility, and better self‐extinguishing properties, but less stability to alkali and acid. Thermal degradation of the typical phosphorus polycarbonates proceeded in two steps, and the activation energies for the maximum rates of weight loss range from 29 to 45 kcal/mole.
Degradation of polymer mixtures. V. Blends of poly(vinyl chloride) with chlorinated rubber
Authors: Dodson B. , McNeill I. C. , Straiton T. 
Published: April 2003

AbstractBlends of PVC with purified commercial chlorinated rubber are substantially less stable than would be predicted from a comparison of the degradations of the constituent polymers. Hydrogen chloride is the sole volatile product in the temperature range of the main degradation reaction. By the use of PVC labeled with 36Cl together with inactive chlorinated rubber, it has proved possible to distinguish the production of hydrogen chloride from the PVC from that from the other polymer. In this way it has been established that it is the PVC component which is responsible for the greatly increased production of hydrogen chloride. Explanations are advanced for the effect of chlorinated rubber in destabilizing the PVC.
Synthesis of a pyrrolone‐type polymer containing anthraquinone units in molten antimony trichloride
Authors: Bruma Maria , Marvel C. S. 
Published: April 2003

Abstract1,2,5,6‐Tetraaminoanthraquinone and 1,4,5,8‐naphthalenetetracarboxylic acid dianhydride react in molten antimony trichloride to give a soluble polypyrrolone structure with an inherent viscosity of 0.4–0.7. Polymers having the viscosity of 0.7 can be wetspun into fibers from molten antimony trichloride or from methanesulfonic acid; also the polymer can be reduced with sodium dithionite in alkaline aqueous dimethyl sulfoxide to give a viscous solution which can be spun into brittle fibers.
Radiation‐induced ionic polymerization of isobutyl vinyl ether in bulk
Authors: Du Plessis T. A. , Stannett V. T. , Goineau A. M. 
Published: April 2003

AbstractThe radiation‐induced ionic polymerization of isobutyl vinyl ether was investigated under conditions where the monomer was dried with molecular sieves. The investigation covered the temperature range from −16°C to 90°C, and the dose‐rate range from 1015 to 1020 eV/g‐sec, using both γ‐rays and electrons. A very high overall activation energy of 15.9 kcal/mole was found for the process below 30°C. Above 30°C, however, the value of the overall activation energy dropped to 4.9 kcal/mole, a phenomenon which is ascribed to the solvation of the propagating carbonium ion below 30°C. The dose‐rate dependence of the rate of polymerization was found to be 0.58 over the entire dose‐rate range investigated. The molecular weight of the polymer was found to be far less sensitive to trace amounts of water than the rate of polymerization. The molecular weight of the polymer depended strongly on the irradiation temperature, reaching a maximum value of about 120,000 at 35°C. It is shown that at temperatures above 20°C regenerative chain transfer processes play an important role in determining the molecular weight of the polymer.
Sorption of gaseous ammonia on sulfonated macroreticular ion exchangers
Authors: Prokop Z. , Setíanek K. 
Published: April 2003

AbstractThe amount of gaseous ammonia sorbed on dry sulfonated macroreticular ion exchangers with different contents of divinylbenzene was found to be greater than the number of sulfonic acid groups. The excess ammonia could be removed by washing with water. With ion exchangers containing more than 20% of divinylbenzene a certain amount of chemically bonded ammonia could not be removed, even by elution with strong acid. Sorption of ammonia occurred also on dry ion exchangers fully neutralized with sodium ion, and in that case also, ammonia could only partially be removed by water from higher crosslinked samples. On desorption into a gaseous phase the amount of desorbed ammonia was proportional to the surface area of the ion exchanger, since desorption occurred only from surface layers. The results obtained indicate that ammonia migrates among acid groups located within the mass of the ion exchanger.
Swelling measurement of some ethylene copolymers crosslinked by dicumyl peroxide
Authors: Senuma Akitaka 
Published: April 2003

AbstractSwelling equilibrium of crosslinked ethylene copolymers prepared by the curing of ethylene–vinyl acetate (EVA), ethylene–ethyl acrylate (EEA), and ethylene–acrylic acid (EAA) with dicumyl peroxide (DCP), has been measured in toluene at 23°C. The stress–strain behavior of the swollen EVA and EEA networks was in accord with that predicted from the statistical rubber elasticity theory, while that of the swollen EAA network was divergent. The concentration dependence of the polymer–solvent interaction parameter for the EAA network–toluene system was observed to be highest, while that for the EVA network–toluene system remained nearly zero. The order of the reactivity of pendant groups in the copolymers by radicals from DCP was estimated to be carboxyl > acetyloxy > ethoxycarbonyl group.
Salt‐catalyzed addition reaction of monoepoxides with philosamia cynthia ricini and bombyx mori silk fibroins
Authors: Tanaka Yoshio , Shiozaki Hideki 
Published: April 2003

AbstractThe heterogeneous addition reaction of various monoepoxides with silk fibroins of Philosamia cynthia ricini and Bombyx mori was investigated at 45–75°C by use of aqueous solutions of various salts as padding catalysts. The effects of salt on the epoxide–silk fibroin reactions were attributed mainly to the nucleophilicity of the anions and also to the acidity or the electronegativity of the cations. The effect of the substituent of the epoxide on the add‐ons was elucidated by the modified Taft equation, (log W − log W0)/σ* = ρp + ρsEs/σ*, where W0 and W are the add‐ons for the reaction of a given compound and of its substituted derivatives, σ* and Es are the polar and the steric substituent constants, ρp and ρs are the polar and the steric reaction constants, respectively. Histidine, lysine, arginine, tyrosine, serine, and acidic amino acids were found to react. The reactivity difference between Philosamia cynthia ricini and Bombyx mori fibroins towards the epoxide was discussed in the light of the observed phenomena.
Starch and amylose degradation by 60Co γ‐irradiation
Authors: Hofreiter B. T. 
Published: April 2003

AbstractThe effects of γ‐irradiation (0.02–4.0 Mrad absorbed dose and 1.2 Mrad/hr dose rate) on depolymerization and selected physical properties of corn starch and amylose (both dry solid and solution forms) were investigated under conditions used to make graft polymers. Radiation introduces an alkali‐sensitive structure, most likely β‐alkoxycarbonyl, having a G value of 2.8. A dimethyl sulfoxide (DMSO)‐acetic acid‐water solvent for intrinsic viscosity was developed that degraded irradiated amylose less than did aqueous 90% DMSO. The G (scission) value of 1.3 for solid amylose irradiated at 0°C under nitrogen is lower than most literature values for either amylose or other polysaccharides. The protection of amylose against irradiation degradation in water by additions of DMSO is noteworthy. The G (scission) for amylose irradiated in 99.8% DMSO is 2.3; whereas, in water it is 30.
Conformational transition of poly(methacrylic acid) in methanol–water mixtures
Authors: Braud Christian , Muller Guy , Fenyo Jean‐Claude , Selegny Eric 
Published: April 2003

AbstractThe effect of ionization on the potentiometric and viscometric behavior of both poly(methacrylic acid) (PMA) and poly(acrylic acid) (PAA) was investigated in methanol–water mixtures. The potentiometric and viscosity data revealed that the conformational change which takes place for PMA in water gradually disappears with increasing content of methanol in methanol–water mixtures. For mixtures containing 40 and 50% methanol, the behavior of PMA solutions becomes similar to that of PAA, i.e., the discontinuity versus the degree of ionization is no longer detectable and the molecule unfolds regularly upon ionization. The addition of methanol leads to the breakdown of the compact structure of PMA which is stabilized, at low degree of ionization in water, by nonelectrostatic interactions between the methyl groups of PMA.
Terpolymerization of sulfur dioxide or maleic anhydride with unsaturated compounds under ultraviolet irradiation
Authors: Furukawa Junji , Kobayashi Eiichi , Nakamura Morio 
Published: April 2003

AbstractThe effect of ultraviolet irradiation on the terpolymerization was investigated. In the terpolymerizations of sulfur dioxide–butene‐1–acrylonitrile, sulfur dioxide–butene‐1–n‐butyl acrylate, and maleic anhydride–allyl chloride–acrylonitrile systems, the composition of the terpolymers prepared under ultraviolet irradiation was different from those prepared in the dark. The unit content of sulfur dioxide and butene‐1 or of maleic anhydride and allyl chloride in the terpolymer increased under ultraviolet irradiation. The nature of the growing end under ultraviolet irradiation is supposed to be the same as that of the dark polymerization on the basis of the same solvent effect on the terpolymer composition, the rate of polymerization and the molecular weight of polymer. The experimental results suggest that the complex between sulfur dioxide and butene‐1 or maleic anhydride and allyl chloride might be excited by ultraviolet light and the excited complex may participate in the terpolymerization.