bluuebunny/crossref_metadata_2025 huggingface dataset:
Chromocene‐based catalysts for ethylene polymerization: Thermal removal of the cyclopentadienyl ligand
Authors: Karol Frederick J. , Wu Chisung
Published: April 2003

Thermal aging of a chromocene catalyst, (C5H5)2Cr/SiO2, in an inert atmosphere leads to a modified catalyst which shows poor response to hydrogen as a transfer agent. Polyethylenes prepared at a polymerization temperature of 90°C with this modified catalyst have a low melt index and high vinyl unsaturation level. By thermogravimetry the weight loss of the catalyst, relative to dehydrated silica, was equivalent to loss of one cyclopentadienyl ligand per chromium site. Pyrolytic gas chromatography showed cyclopentadiene was liberated in the thermal process. These overall studies provide strong evidence that loss of a cyclopentadienyl ligand in supported chromium catalysts has a profound effect on overall polymerization behavior.
A novel scheme of heterogeneous polymerization of ethylene
Authors: Watanabe Terutaka , Wada Takeshi , Takehisa Masaaki , Machi Sueo
Published: April 2003

The heterogeneous polymerization of ethylene initiated by radiation in tert‐butyl alcohol was studied. The polymerization was carried out in a 100‐ml reactor at 25–100°C and pressures of 200–300 kg/cm2 in the presence of 50 ml of tert‐butyl alcohol containing 7 wt‐% water. The amounts of polymerized monomer, the average molecular weight of polymer formed, and the molecular weight distribution of polymer were measured at various stages of reaction and at various temperatures. The molecular weight distribution was found to be very much dependent on the reaction time and temperature. For the polymer formed at 50–60°C in the very early stages of reaction, the molecular weight distribution is unimodal, and in the intermediate stage a shoulder appears at a molecular weight higher than the first peak which increases as the polymerization proceeds; eventually a bimodal curve is formed. The bimodal distribution curves were analyzed to determine the fractions and average molecular weights of the each peak. On the basis of these data for the molecular weight distribution and kinetic behavior, a new scheme for the heterogeneous polymerization is proposed which indicates that the polymerization proceeds via propagating radicals in two different physical states, namely, loose and rigid states.
Polymerization of vinyl chloride by use of modified Ziegler–Natta catalysts. I. Overall kinetic features
Authors: Chesworth A. G. , Haszeldine R. N. , Tait P. J. T.
Published: April 2003

Vinyl chloride has been polymerized by a modified Ziegler‐Natta type catalyst VOCl2 · 2THF–Al(i‐Bu)3–THF, and the kinetics of the polymerization reaction have been investigated in some detail. The present kinetic analysis has demonstrated that the generation of active centers is directly proportional to the catalyst concentration, and that their depletion is by a second‐order decay process. Triisobutylaluminum has been found to contribute to the effective removal of active centers through complex formation.
Photochemical polymerization of gaseous ethyl acrylate
Authors: Dixon G. Douglass
Published: April 2003

Exposure of gaseous ethyl acrylate to ultraviolet radiation causes deposition of poly(ethyl acrylate) at a rate depending on a number of parameters, including the wave‐length of the radiation, its intensity, and exposure time. The rate also depends upon the monomer pressure and the presence of contaminants, most notably moisture and oxygen.
Stereoregularity of poly(alkyl α‐chloroacrylates) and mechanism of isotactic polymerization
Authors: Uryu Toshiyuki , Ohaku Ken‐Ichi , Matsuzaki Kei
Published: April 2003

The catalytic activity of the complexes prepared by the reaction of Grignard reagents with ketones, esters, and an epoxide as polymerization catalysts of methyl and ethyl α‐chloroacrylates was investigated. The modifiers which gave isotactic polymers were α,β‐unsaturated ketones such as benzalacetophenone, benzalacetone, dibenzalacetone, mesityl oxide, and methyl vinyl ketone, and α,β‐unsaturated esters such as ethyl cinnamate, ethyl crotonate, and methyl acrylate. Catalysts with butyl ethyl ketone, propiophenone, and propylene oxide as modifiers produced atactic polymers but no isotactic polymers. It was revealed that the complex catalysts having a structure CCOMgX (X is halogen) gave isotactic polymers. The mechanism of isotactic polymerization was discussed. In addition, for radical polymerization of ethyl α‐chloroacrylate, enthalpy and entropy differences between isotactic and syndiotactic additions were calculated to give ΔHi* − ΔHs* = 910 cal/mole and ΔSi* − ΔSs* = 0.82 eu.
Linear polyesters containing isocyanurate rings
Authors: Kauffman W. J.
Published: April 2003

Two series of linear polyesters containing isocyanurate rings have been prepared to determine the effect of structural variations on thermal and solubility properties. The polyesters were prepared by the polycondensation reaction of isocyanurate containing difunctional acid and ester monomers with linear diols. The substituent on the isocyanurate ring and the length of the acid side chain have been shown to have considerable effect on the glass transition temperature Tg. Different solubility properties were observed for the series of polyesters in which the pendant substituent was C6H5 and the acid side‐chain was CH2CO2H. These polymers were insoluble in THF, and the polyester prepared from 1,6‐hexanediol was also insoluble in chloroform. Thermal gravimetric analysis (TGA) indicated that structural differences had no significant effect on the thermal stability of these linear polyesters.
Polymerization of acetylenes catalyzed by arene–group vib tricarbonyls
Authors: Woon Paul S. , Farona Michael F.
Published: April 2003

The polymerization of phenylacetylene and other terminal and internal alkynes has been achieved in homogeneous reactions catalyzed by ArM(CO)3, where Ar is an arene; M is Cr, Mo, or W. The polymerization of phenylacetylene proceeds by way of an intermediate which has been isolated and identified as a ladder compound composed of fused cyclobutane rings. The ladder compound, which is stable in the absence of the catalyst, breaks down in the presence of the catalyst to give the final polyconjugated polymer. Available evidence indicates that the conversion of the ladder compound to polyphenylacetylene proceeds by way of a free‐radical mechanism. A mechanism for the electronic conversion of the ladder compound to the final polymer is proposed, as is a method of chain propagation.
Photosensitized copolymerization of optically active N‐l‐menthylmaleimide with styrene and methyl methacrylate
Authors: Sakota Naokazu , Kishiue Kiyoshi , Shimada Shyozo , Minoura Yuji
Published: April 2003

Photosensitized copolymerization of optically active N‐l‐menthylmaleimide (NMMI) with styrene (Sty) and methyl methacrylate (MMA) was carried out in tetrahydrofuran (THF) at 30°C with benzoyl peroxide (BPO). The monomer reactivity ratios for the copolymerization of NMMI (M2) with Sty (M1) and MMA (M1) were r1 = 0.08 ± 0.10, r2 = 0.20 ± 0.05 and r1 = 2.85 ± 0.06, r2 = 0.07 ± 0.06, respectively. Copoly‐MMA–NMMI and poly‐NMMI showed positive circular dichroism(CD) curves of equal intensity and shape over the wavelength region from 230 to 270 nm; copoly‐Sty–NMMI also showed a positive CD curve which was similar in shape but was different in intensity from that of poly‐NMMI. The correlation between monomer unit ellipticity of the copolymers and their composition would suggest the alternating and stereoregular copolymerization of NMMI with Sty.
Heat‐resistant polymers containing bipyridyl units. III. Polyimides having o‐, m‐, or p‐phenylenedioxy linkage
Authors: Kurita Keisuke , Williams Roy L.
Published: April 2003

New series of diamines having pyridine rings and o‐, m‐, or p‐phenylenedioxy linkages were prepared by condensation of chloronitropyridine with isomeric dihydroxybenzenes followed by chemical reduction. The polymerization of the diamines with benzo‐phenonetetracarboxylic acid dianhydride gave polyamic acids with the inherent viscosities in the range 0.21 to 1.30 dl/g. The conversion of these polyamic acids to polyimides was carried out thermally and the resulting polyimides exhibited very good solubility in organic solvents.
Reaction of poly(vinyl alcohol) with potassium persulfate and graft copolymerization
Authors: Ikada Yoshito , Nishizaki Yasuko , Sakurada Ichiro
Published: April 2003

A study of the oxidation of poly(vinyl alcohol) (PVAL) by potassium persulfate (KPS) in aqueous solutions showed that the decomposition of KPS was greatly enhanced by the presence of PVAL, its hydroxyl groups being oxidized to ketones in a yield of about one mole of ketone from one mole of KPS. The decomposition rate of KPS was found to be given by the equation, −d[S2O82−]/dt = k[S2O82−] [PVAL]1/2, which was essentially the same as in the oxidation of alcohols of low molecular weight by persulfate ion. The occurrence of gelation of PVAL solutions and graft copolymerization of methyl methacrylate (MMA) onto PVAL in the presence of KPS was evidence for PVAL radical as an intermediate species in the oxidation of PVAL. A characterization study was also carried out for the reaction products of the graft copolymerization of MMA onto PVAL with KPS in dimethyl sulfoxide solution.
Stationary copolymerization of formaldehyde and 1,3‐dioxolan
Authors: Penchev P. I. , Minin V. A. , Kedrina N. F. , Ivanov V. V. , Enikolopyan N. S.
Published: April 2003

A. study on the kinetics of gas‐phase copolymerization of formaldehyde and 1,3‐dioxolan effected by stannic chloride in a flow reactor with ideal mixing is reported. Equations were calculated describing the run of process depending on the composition of the outgoing flow measured with a gas chromatograph. It was established that the reaction takes place under stationary conditions. The change of the degree of conversion of monomers, and composition of the stable portion of the copolymer, and copolymer molecular weight with catalyst concentration was examined. It was shown that a kinetic and diffusion area may be possible. A product of high molecular weight and thermostability was obtained. The molecular size distribution was ascertained to be close to the exponential type. The average number of blocks and units of both monomers was calculated. Different posteffects for the two reacting substances were found.
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

The 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

Two 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

4,4′‐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

Polypentenamers 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

Details 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

The 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

Polystyrenes 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

The 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

The 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

Cellobiose 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

The 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

Aromatic 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

Blends 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

1,2,5,6‐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

The 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

The 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

Swelling 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

The 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

The 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

The 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

The 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.
Bridged polyaromatics: Synthesis, structure, and isomorphous properties of methyl‐substituted polymers containing CH2, O, and S bridges
Authors: Montaudo G. , Bruno G. , Maravigna P. , Bottino F.
Published: April 2003

Linear, crystalline polymers corresponding to the general formulas
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where X is CH2, O, or S, were synthesized, and their isomorphous relationships were studied. The results point out that a close structural relationship exists within each series of compounds investigated.
Monte Carlo studies of nonstationary polymerization processes. I. Grafting of styrene onto preirradiated cellulose acetate
Authors: Yasukawa Tamio , Sasaki Yasunori , Murakami Kenkichi
Published: April 2003

The molecular weight distribution (MWD) of polystyrene grafted onto 4 Mrad‐preirradiated cellulose acetate at 50°C has been calculated on the basis of simulating reaction with several models. A model in which the coupling probability of graft radicals is proportional to the reciprocal of the square root of chain length and the growth rate is dispersed widely around the average value gave a MWD which agreed fairly well with observation. Several factors which affect the MWD of graft chains are also discussed on the basis of simulated reactions.
Application of Bender's salts to the synthesis of S‐vinyl‐O‐tert‐alkylthiocarbonates
Authors: Daly W. H. , Lee Chien‐Da S.
Published: April 2003

Three thermally labile Bender's salts were synthesized and utilized to effect quantitative SN2 displacement of primary halides to form tert‐alkylthiocarbonate derivatives. Selective displacement of bromide from 1,2‐bromochloroethane by either VI or VII followed by dehydrohalogenation with potassium tert‐butoxide yielded S‐vinyl‐O‐tert‐butylthiocarbonate (I) and S‐vinyl‐O‐tert‐amylthiocarbonate (X), two excellent vinyl monomer precursors for polymercaptan, in 62 and 51% yield, respectively. Reaction of VI with vinylbenzyl chloride yielded S‐(vinylbenzyl)‐O‐tert‐butylthiocarbonate which polymerized in the presence of free radical initiators to produce a poly(vinylbenzyl mercaptan) precursor. Dilatometric studies of the homopolymerization of I demonstrated that the polymerization rate was proportional to [I]0.765 and [M]1.7, respectively; the monomer exhibited a high chain transfer constant (CM = 3.9 × 10−3).
NMR and ESR studies of the solid‐state polymerization of vinyl monomers. III. Methacrylic acid
Authors: Chachaty C. , Latimier M. , Forchioni A.
Published: April 2003

The kinetics of postpolymerization of γ‐irradiated methacrylic acid at 77°K has been investigated by wide‐line NMR and by ESR spectroscopy. The conversion yield was continuously measured in the temperature range of 260–280°K, from the narrowing of the NMR spectrum due to the progressive “amorphization” of the matrix, releasing the motion of monomer molecules. The rate of postpolymerization decays exponentially with time, independently of the recombination of free radicals. The local concentration of radicals remaining after prolonged annealing is actually the same as initially, showing that no recombination occurs in the microdomains of polymerization. The 13C NMR study of the poly(methacrylic acid) formed by solid‐state polymerization shows a predominent syndiotactic character, with an increasing contribution of isotactic sequences as the postpolymerization temperature is lowered.
Stress–strain relations of crosslinked rubbers under different types of strain
Authors: Bartenev G. M. , Nikiforov V. P.
Published: April 2003

Experimental data for the stresses and the deformations for crosslinked rubbers at uniaxial and symmetrical and asymmetrical biaxial extension and pure shear are given. Stressed states up to 100% extension are described by a single parameter, the highly elastic potential of Bartenev and Khazanovich. The classical statistical potential of Kuhn‐James‐Guth‐Treloar is not in agreement with experimental data, as shear modulus G has different values for different types of stressed states.
Synthesis and polymerization of allyloxyacetaldehyde
Authors: Sumitomo Hiroshi , Hashimoto Kazuhiko , Kitao Osamu
Published: April 2003

Allyloxyacetaldehyde (AOA) was synthesized by the Williamson reaction between sodium allyl alcoholate and bromoacetaldehyde dimethyl acetal. Highly reactive crystalline poly(allyloxymethyl)oxymethylene was obtained from AOA by using organoaluminum compounds as initiators at low temperature. The influence of initiators, solvents, and temperature on the polymerization was examined. Conspicuous exothermal behavior of the resulting polymer observed in the temperature range of 110–140°C in air with a differential scanning calorimeter, was not only due to an oxidative scission of the polyoxymethylene chain but also due to a chain reaction of neighboring allyl side groups in the polymer chain.
Synthesis of polyimides from N,N′‐bis(phenylsulfonyl)pyromellitimide and aromatic diamines
Authors: Imai Yoshio , Ishimori Motokazu
Published: April 2003

A novel and successful synthesis of polyimide has been performed by the two‐step polymerization of N,N′‐bis(phenylsulfonyl)pyromellitimide (BPSP) and bis(4‐aminophenyl) ether (ODA). The ring‐opening polyaddition reaction proceeded in N‐methyl‐2‐pyrrolidone at room temperature through the formation of the open‐chain polyamide, which was subsequently converted by heating to the polyimide along with the elimination of benzenesulfonamide. The polymerization of BPSP with ODA took place fairly rapidly to give the polyamide having inherent viscosity in the range of 0.6–0.8. The polyamide solution was resistant to hydrolysis, but was somewhat susceptible to imidization reaction. The thermal imidization of the open‐chain polyamide occurred far more readily than that of the polyamic acid derived from pyromellitic dianhydride and ODA.
Temperature dependence on the binding of butyl orange by bovine serum albumin: The effect of urea
Authors: Takagishi Toru , Takami Katsushige , Kuroki Nobuhiko
Published: April 2003

The effect of urea on the extent of the binding of butyl orange by bovine serum albumin has been examined by an equilibrium dialysis method. The first binding constants and the thermodynamic parameters for the formation of the first dye anion–protein complex have been calculated. Addition of urea to the binding system causes a marked decrease in the absolute magnitude of the free energy change. The enthalpy change during binding becomes more exothermic, and the entropy change tends to decrease with increasing concentration of urea. These results can be interpreted in terms of the concept that urea reduces the structure of the aqueous environment and hence lowers the tendency of apolar groups of the dye and the albumin to participate in the formation of hydrophobic interactions.
Calorimetric investigation of polymerization reactions. V. Crosslinked copolymerization of methyl methacrylate with ethylene dimethacrylate
Authors: Horie Kazuyuki , Otagawa Atsushi , Muraoka Minoru , Mita Itaru
Published: April 2003

The crosslinked copolymerization of methyl methacrylate with ethylene dimethacrylate (EDMA) in bulk and in toluene has been investigated by differential scanning calorimetry. The appearance of a second peak, in addition to that arising from the gel effect, noted in curves of bulk copolymerization rate (fraction of EDMA mE = 0.20) is explained by the formation of microgels during the copolymerization. With mE = 0.50–1.00, copolymerization proceeds heterogeneously at first, providing opaque microgels, which become transparent polymer in a later stage at a weight fraction of toluene wT ≦ 0.20 and independent polymer particles at wT ≧ 0.30. A diagram is given which illustrates three types of copolymerization depending on initial composition of monomers and toluene. Final conversions for mE ≦ 0.10 agree well with predictions. Copolymerization at mE ≧ 0.20 ceases because of reduction of segmental mobility due to dense network formation in microgel, though the whole system is not yet in glassy state. Data of final conversions in solution copolymerization also support the above mechanism.
Initiated oxidation of solid polystyrene and the effect of antioxidants on this process
Authors: Pokholok T. V. , Karpukhin O. N. , Shlyapintokh V. Ya.
Published: April 2003

The paper is concerned with the kinetics of radical conversions in solid polystyrene (PS) induced by decomposition of free‐radical initiators over the temperature range of 60–90°C. A complex quantitative study of PS oxidation was carried out. The kinetics of initiator decomposition and of hydroperoxide accumulation, the variations in chemiluminescence (CL) intensity accompanying polymer oxidation were studied. The CL spectrum and the changes in molecular weight in the course of oxidation were measured. A method for determination of the relative antiradical activity of antioxidants, based on the competition between the antioxidant and the stable radical for the active radical was proposed. The activity of valence‐saturated antioxidants in the solid phase was found to become more uniform compared to the liquid phase, whereas that of stable nitroxide radicals was abnormally high. Initiated solid PS oxidation occurred by a chain mechanism with formally linear termination of the chain. The chain length of 3.0 ± 0.5 was independent of temperature. A model of initiated PS oxidation is proposed. It implies structural inhomogeneity of the sample, resulting in different probabilities of radical formation in the polymer bulk in the course of initiator decomposition in various sample zones. The model permits quantitative description of the kinetics of hydroperoxide accumulation, stable radical consumption, and of variations in CL intensity during initiated and inhibited PS oxidation.
Pyrolsis of a flexible urethane foam
Authors: Hileman F. D. , Voorhees K. J. , Wojcik L. H. , Birky M. M. , Ryan P. W. , Einhorn I. N.
Published: April 2003

Pyrolysis of a commercial flexible urethane foam in an inert atmosphere was investigated by use of GCMS and chemical ionization mass spectroscopy. Pyrolysis products were identified and quantified at four pyrolysis temperatures. A mechanism is discussed in terms of the identified products.
Polymer combustion
Authors: Stuetz D. E. , Diedwardo A. H. , Zitomer F. , Barnes B. P.
Published: April 2003

Experimental conditions have been defined for the steady‐state combustion of vertically positioned polymer rods burning at the top surface. Temperature and composition profiles through solid and gas phases of the system, polymer consumption rate, and flame height were measured, and the response of these parameters to changes of the oxygen concentration in the environment were determined. Measurements showed that unreacted oxygen diffused from the environment to the burning surface and was absorbed into the polymer, forming a well defined oxygen‐rich layer. Concentration of chemically bound oxygen at the surface of this layer were high, e.g., with polypropylene ca. 26 wt‐%, and identical with the stoichiometry of the gases leaving the surface and serving as fuel for the flame. The composition of the gas phase at the surface indicated the conversion of 11.4% of the hydrocarbon fuel to CO, CO2, and H2O. An energy balance for the system confirmed that fuel production in this surface layer takes place via simultaneous oxidative and pyrolytic degradation of the polymer, with exothermic processes supplying the energy for endothermic processes. Conductive and radiative contributions from the gas phase were found to play a minor role in maintaining fuel formation. The rate of degradation of a polymer to fuel, normalized to the area of the burning surface, was found to be independent of polymer supply rate and to increase with the oxygen concentration in the environment. The degradation process was successfully modeled in TGA experiments at temperatures and oxygen concentrations representative of the burning surface. The existence of an oxidative surface layer was confirmed and the TGA degradation rate related to the surface‐to‐volume ratio of the polymer sample. Compositional analysis of a methane diffusion flame of a geometry identical to that of the polymer flame, revealed the presence of unreacted oxygen throughout the preheating zone and at the surface of the burner. Conversion of fuel to final combustion products at the surface was 6.3%. Temperature and composition changes as a function of oxygen concentration in the environment were determined and compared with the polymer diffusion flame. It was concluded that a polymer flame, because of its autogenerative fuel production, possesses only one degree of freedom, viz., the oxygen concentration in the environment, in contrast to the conventionally fueled diffusion flame for which fuel supply rate is an additional independent parameter. Due to this single degree of freedom, the sensitivity of the polymer flame to environmental influences is increased. Effects caused by these extrinsic factors will be the subject of a separate report.
Crystallizability and thermal properties of phosphorus‐containing polyamides
Authors: Shalaby S. W. , Turi E. A. , Riggi M. H. , Harget P. J.
Published: April 2003

Bis(2‐carb‐n‐butoxyethyl)methylphosphine oxide was prepared and condensed with 1,2‐diaminoethane, 1,6‐diaminohexane, 1,8‐diaminooctane, 1,10‐diaminodecane, and 1,12‐diaminododecane to form polyamides with an increasing number of methylene groups between the amide moieties. Polyamides made from the 1,10‐ and 1,12‐diaminoalkanes were shown by x‐ray and DSC to be semicrystalline, while those based on the 1,6‐ and 1,8‐diaminoalkanes were amorphous to x‐ray and revealed no first‐order transitions. The repeat distances of the crystalline polymers were determined, and an extended planar zigzag conformation was excluded as a possible conformation for these polymers. The thermal stability of the phosphorus‐containing polyamides, in both oxygen and nitrogen, was studied by TGA and the results were correlated with the chemical structure.