bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the theory of divalent ion binding by polyelectrolytes
Authors: Strauss Ulrich P. , Lifson Sheneior 
Published: April 2003

AbstractThe problem of the binding of a divalent counterion by two adjacent binding sites of a uniform linear polyelectrolyte has been investigated for both finite and infinite chain lengths. Allowance has been made for interactions between adjoining ionized groups and for the presence of a univalent counterion which may also be bound. For the case of finite chain lengths, the partition function is obtained in terms of a 3 × 3 matrix containing the conditional probabilities of the possible states of a polyelectrolyte group. By a novel method, the expression for the partition function is then simplified to a finite polynomial containing only the coefficients of the secular equation, but not its eigenvalues. From this expression for the partition function, the quasi‐grand partition function for the infinitely long chain is calculated. It is shown that for both cases of finite and infinite chain length, closed explicit expressions relating the degrees of ionization and ion binding to the ion activities and the interaction parameter may be obtained from which the eigenvalues of the matrix have been eliminated. The applicability of the new method of calculation to other problems involving finite linear Ising lattices is briefly discussed.
Chemically heterogeneous populations of copolymer latex particles. Preparation, fractionation, and characterization
Authors: Yannas J. B. , Isgur I. E. 
Published: April 2003

AbstractThe chemical homogeneity of copolymer latex particle populations was studied as a function of polymerization conditions. The comonomer system chosen was styrene–butadiene, and the polymerization variables included the comonomer addition rate and the amount of emulsifier introduced during the reaction. It was found that under conditions of variable comonomer addition rate and with introduction of excess emulsifier during the reaction, a bidisperse latex is produced which contains two chemically distinct particle populations. These populations were separated from one another using a centrifugation technique reported recently and were characterized by electron microscopy and chemical analysis. Each particle population was relatively monodisperse with respect to particle size and differed from its counterpart with respect to average particle size and comonomer ratio. Other combinations of the polymerization variables mentioned above yielded latices with chemically homogeneous particle populations.
Infrared and nuclear magnetic resonance studies of the microstructures of polychloroprenes
Authors: Ferguson Raymond C. 
Published: April 2003

AbstractHigh resolution infrared and nuclear magnetic resonance spectra confirm the structure of cis‐polychloroprene prepared by a stereospecific route. Head‐to‐tail, head‐to‐head, and tail‐to‐tail sequence isomerism in both cis‐ and trans‐polychloroprenes has been discovered and measured quantitatively by high resolution NMR spectroscopy. The irregularity in the microstructure of neoprenes proves to be more extensive than was previously suspected.
Anionic polymerization and oligomerization of methacrylonitrile by alkali metal alkoxides
Authors: Feit Ben‐Ami , Wallach Joseph , Zilkha Albert 
Published: April 2003

AbstractThe anionic homogeneous polymerization of methacrylonitrile by alcoholic solutions of alkali metal alkoxides in dimethylformamide was studied. The molecular weight was found to be directly proportional to monomer concentration and inversely proportional to methanol concentration in accordance with the equation DP = (Kp/Kt) [MAN]/‐[CH3OH], as consistent with termination by methanol. The average Kp/Kt value obtained was 2.1–2.2. This low value enabled the formation of low oligomers at relatively high methanol concentrations. This is in contrast with the previous results of a parallel polymerization system with acrylonitrile, where only the cyanoethylation product together with relatively high polymers, and no intermediate oligomers, were formed. The physical properties of the oligomers (n = 2–5) are given.
Amylose V complexes from 2‐aminoethanol solutions
Authors: Valletta R. M. , Germino F. J. 
Published: April 2003

AbstractThe amylose V complexes with methanol, 1‐propanol, 1‐butanol, and acetone have been prepared from 2‐aminoethanol solutions at 95°C. and their unit cell dimensions calculated from their x‐ray powder patterns. The study shows that amylose V complexes having helix diameters of 13.0 A., 13.7 A., and a mixture of 13.7 A. and 13.0 A. can be produced in systems devoid of water. Further, the results indicate that the helix diameter in this system is affected by the temperature of the amylose solution prior to the formation of the V complex. In addition, there seems to be correlation between crystal structure of the amylose, size of its helical diameter, and its conformation in solution.
Salicylaldehyde–formaldehyde polymers and their metallic chelates
Authors: Winslow Eugene C. , Manning Albert A. 
Published: April 2003

AbstractSalicylaldehyde–formaldehyde polymers were prepared with the use of oxalic acid, formic acid, sulfuric acid, and sodium hydroxide as catalysts. A non‐catalyzed polymer was prepared also at an elevated temperature with the use of a pressure bomb. Metallic chelates of the oxalic acid‐catalyzed polymer were prepared with various metallic cations. Each of the polymers was examined for solubility characteristics and for thermal stability. The chelates were similarly examined. The molecular weights of the polymers were in the 700–800 range as determined by freezing point depression. Chelated polymers were stable in air at temperatures which were about 50°C. higher than the decomposition temperature of the corresponding nonchelated polymers.
Electron radiation of aqueous methyl cellulose solutions
Authors: Hillend W. Jack , Swenson Harold A. 
Published: April 2003

AbstractSolutions (4%) of commercial methyl cellulose (85,000 weight‐average moleculas weight) were radiated with electrons under varied atmospheres of oxygen at dose rates of 0.15, 0.45, and 4.5 Mrad/min. to total doses of 0.45, 4.5 and 10.0 Mrad. Sampler irradiated at the highest dose rates formed gels whose strength was estimated in a Brook‐field viscometer. After dispersing by stirring, the gels were clarified by centrifugation before viscosity, light‐scattering, and sedimentation measurements were made. Molecular weight increases to as high as 270,000 were found, and the sedimentation coefficients increased correspondingly. The intrinsic viscosity of the irradiated polymer solutions, on the other hand, did not increase as the molecular weight doubled or tripled. This is interpreted to be the result of recoupling of hydrolyzed fragments to produce branched molecules of smaller volume and greater weight. High dose rates promoted molecular weight increases while the presence of oxygen, low dose rates, and low polymer concentration favored degradation. The carboxyls evidently produced in the oxidative degradation resulted in a lowered pH of the irradiated solution and in polyelectrolyte viscosity behavior. Boiling an irradiated polymer solution at pH 10.5 reduced molecular weight from 270,000 to 165,000, showing the presence of alkali‐labile as well as alkali‐stable bonds. The gels on the other hand could be dispersed by stirring or heat as well as by alkali. Although branching may affect gelation to some extent, the molecular weight and sedimentation of the samples in solution appear to be approaching a maximum at the dosage level where the more labile bonding of the gelation phenomenon sets in.
On the deformation of networks of very stiff random chains existing in certain colloidal gels
Authors: Hermans Jan 
Published: April 2003

AbstractThe deformation of the random chains consisting of stiff particles which occur in gels of certain colloids is analyzed. The results of this analysis are used to obtain an expression for the elasticity modulus of infinite networks consisting of such chains. It is found that the shear modulus is proportional to the number of chains between crosslinks per unit of volume and to the average inverse length of the chains.
Polymer degradation. II. Mechanism of thermal degradation of polyoxypropylene glycol–toluene 2,4‐diisocyanate polymer (POPG–TDI) and a block polyether glycol–TDI polymer
Authors: Ingham J. D. , Rapp N. S. 
Published: April 2003

AbstractFurther studies on the thermal degradation of POPG‐TDI polymer have been carried out. It has been shown that at temperatures of ∼200°C., the predominant degradation process involves random scission of the urethane linkages to give substantial amounts of isocyanate and hydroxyl. Kinetic data suggests that the weakest links in POPG‐TDI polymer are spaced at intervals of ∼10,000 in molecular weight and that they may be eliminated by pretreatment of the POPG with ethylene oxide to form a block copolyether which is used to prepare the polyurethane. At temperatures exceeding 250°C. and a greater conversion to volatile fragments (>10%) the kinetics of degradation of POPG‐TDI are similar to results for POPG and indicate scission of the polyether bonds by a combination of intramolecular proton abstraction and free radical unzipping reactions, in agreement with previous studies of POPG of much higher molecular weight.
Diffusion of oxygen in gamma‐irradiated polyethylene
Authors: Giberson R. C. 
Published: April 2003

AbstractTheories of gas flow in polymers developed by Michaels and co‐workers have been used to calculate the diffusion coefficient for oxygen in γ‐irradiated polyethylene. The value obtained is in good agreement with that obtained from an independent method. The possible effect of dose rate on Michaels' theories is presented.
Synthesis and characterization of poly‐s‐triazinyleneimides
Authors: Ehlers Gerhard F. L. , Ray James D. 
Published: April 2003

AbstractPoly‐s‐triazinyleneimides have been prepared from melt reactions between aminoand chloro‐substituted s‐triazine derivatives. The polymers, which have been characterized by melting ranges, inherent viscosity, solubility, elementary analysis, and thermogravimetric analysis, are brittle resins of relatively low molecular weight. Poly‐6‐phenyl‐N‐methyl‐2,4‐s‐triazinyleneimide, with an inherent viscosity of 0.35, had the highest molecular weight of the polymers synthesized. Poly‐6‐chloro‐N‐phenyl‐2,4‐s‐triazinyleneimide, exhibited considerable mechanical strength at room temperature, apparently due to strong secondary bonding forces.
Investigations on the continuous copolymerization of acrylonitrile with methyl methacrylate in a heterogeneous system
Authors: Bero Maciej , Laczkowski Marceli , Pstrocki Henryk 
Published: April 2003

AbstractInvestigations were carried out on continuous copolymerization of acrylonitrile with methyl methacrylate in a tank type reactor and in a heterogeneous system. It was found that the reaction rate of copolymerization is directly proportional to the concentration of comonomers in the reactor and proportional to the residence time to the −0.65 power. Investigations on the influence of the concentration of initiator upon the reaction rate gave evidence of a change in the mechanism of termination reaction at higher concentrations of initiator in the system. The molecular weights of the copolymers, at sufficiently long residence times, were constant. The composition of the copolymers obtained was in accordance with theoretical anticipations. Some discrepancies between the equations derived and the experimental results were tentatively explained on the basis of the influence of the heterogeneous nature of the system.
Graft copolymerization of vinylpyrrolidone onto polydimethylsiloxane
Authors: Yasuda H. , Refojo M. F. 
Published: April 2003

AbstractGraft copolymers of polyvinylpyrrolidone (PVP) onto polydimethylsiloxane have been prepared by the mutual irradiation technique utilizing high energy electrons (3 M.e.v.) generated by Van de Graaf. Water has been shown to have an acceleration effect of polymerization of vinylpyrrolidone and a reduction in the penetration of the monomer solution in the polymer. The dependence of the molecular weight of polyvinylpyrrolidone on the dose, and the dependence of the penetration of the grafted layer in the trunk polymer on the dose and the water content in the monomer solutions have been determined. The graft copolymers are hydrophilic and their hydrophilicity is proportional to the amount of polyvinylpyrrolidone grafted onto the silicone. The location of the graft copolymer is determined by staining and sectioning and sectioning technique. Grafting varied from surface grafting to apparently homogeneous grafting depending on the water content in the monomer solution and on the total dose.
Study of crosslink formation by partial conversion properties I. Copolymerization of poly(ethylene fumarate) and styrene
Authors: Burnett G. M. , Hay J. N. , Smith J. D. B. 
Published: April 2003

AbstractThe copolymerization reaction of poly(ethylene fumarate) and styrene has been studied in dilute solution by the change in number‐average molecular weight with conversion. The partial conversion molecular weight is found to vary with conversion and to be a guide to the overall reaction mechanism, which is that of crosslink formation.
Heats of mixing of polymers with ester and ether solvents
Authors: Patterson D. 
Published: April 2003

AbstractHeats of mixing at infinite dilution have been obtained for polydimethylsiloxane in four series of ester solvents: the methyl and ethyl esters of the aliphatic acids, and the acetic and propionic esters derived from the normal alcohols. Heats have also been obtained in certain ethers including the dialkyl ethers. The solvent molecules are considered to be chains of two types of segments: CH2CH2 and COO, or CH2O. The heat of mixing is ascribed to two contributions: I, a difference in force fields between segments of polymer and solvent molecules, and II, a difference in the Prigogine structural factors of the molecules. Contribution II has been assumed to be approximately the same as with n‐alkane solvents of corresponding chain lengths. By subtracting heats found with n‐alkane solvents from those with esters or ethers II is eliminated and the resulting difference in I may be treated using a lattice model and assuming random mixing. This approach is successful for the ester solvents but somewhat less so for the ethers, where some departure from randomness due to steric factors may be present.
Electrochemical transformations of polymeric acid solutions. I. Crossed Koble synthesis
Authors: Smets G. , Van der Borght X. , Van Haeren G. 
Published: April 2003

AbstractPoly(methacrylic acid) was electrolyzed at 20°C. in 0.2 M dry methanol solution in a glass apparatus provided with two polished platinum disk electrodes; the current density was kept constant (300, 800, or 1000 ma.). Before electrolysis the acid was partially neutralized in order to increase the electrical conductivity. The electrolysis was characterized by evolution of carbon dioxide at the anode, while the acid content of the polymer decreased. When the degree of decarboxylation was about 30%, intramolecular lactonization occurred by interaction of unsaturated groups with neighboring acid groups. The changes of chemical composition of the polymer in function of the time were followed by determination of free carboxylic acid groups, of γ‐lactones, and unsaturated groups (bromine addition). The amount of methyl ester formed by methanolysis of the lactones was calculated from methoxyl determinations. At the end of electrolysis only 5–6% free carboxylic groups were present, 35–40% lactones, 30% ester groups; the residue was mainly a hydrocarbon fraction (partially unsaturated). The electrolysis was also carried out in the presence of low molecular weight carboxylic acids, acetic, ϵ‐acetaminocarproic, and cyanoacetic acids, the ratio of the concentration of these acids to that of polymeric acid being varied over a wide range. With acetic acid the chemical composition of the polymer was only slightly affected through grafting of side methyl groups, as was shown by the use of C14 acetic acid. With ϵ‐acetaminocaproic and cyanoacetic acids the crossed Kolbe synthesis reactions are much more important, 20–24% side alkyl acetamino groups and 15% cyanomethylene groups being grafted to the main chain by this method. Chain degradation during these experiments can be practically avoided.
Copolymerization of nonconjugated diolefins: General composition relationships
Authors: Gibbs W. E. , McHenry R. J. 
Published: April 2003

AbstractThe copolymerization of nonconjugated diolefins with vinyl monomers involves departures from conventional vinyl copolymerization kinetics and the standard forms of the binary or ternary copolymerization composition equations are inadequate. These departures include intramolecular cyclization reactions and generally the formation of some pendent double‐bonds. A general treatment of the copolymerization of symmetrical nonconjugated diolefins with vinyl monomers gives closed form relationships which take such reactions and their consequences into account. The general relationships may be approximated by a new series of composition equations which take into account the formation of both cyclized and noncyclized units in the chain and are simple enough for experimental use. The latter expressions are:

where: αc = kc/k11, α4 = k14/k11, δ1 = k41/k44, and β4 = k24/k21, and [M1], [M3], and [M4] refer to the concentrations of diolefin double bonds, pendent double bonds, and comonomer, respectively.
α,ω‐glycols from isobutylene and some derived block copolymers
Authors: Jones E. B. , Marvel C. S. 
Published: April 2003

AbstractButyl rubber containing 2 mole‐% of isoprene was ozonized and reduced producing polyisobutylene glycol. Hydroxyl equivalent determinations on the glycol and elemental analyses of the chain extended polymers indicate the glycol to be difunctional. Possible structures of the glycol and extended polymer are suggested.
Kinetics of the polymerization of divinylbenzene isomers
Authors: Wiley Richard H. , Devenuto Giovanni 
Published: April 2003

AbstractThe overall rates of polymerization of m‐ and p‐divinylbenzene, a 2:1 mixture of the meta and para isomers, and commercial divinylbenzene have been followed viscometrically. Data at 60 and 80°C. show that the meta isomer polymerizes most rapidly. Ratios of rates show differences in activation energies. An effect on the overall rates is tentatively attributed to the increased resonance stabilization of the p‐vinylphenyl‐derived radical which further decreases the already low reactivity of the styrene‐derived radical. The possibility that steric factors contribute significantly to the rate difference is considered to be unlikely.
Some remarks on amorphous and atactic α‐olefin polymers and random ethylene–propylene copolymers
Authors: Natta G. , Valvassori A. , Ciampelli F. , Mazzanti G. 
Published: April 2003

AbstractThe necessity is pointed out to distinguish between an “amorphous” α‐olefin polymer and an “atactic” α‐olefin polymer. It is convenient to limit the term “atactic” only to those amorphous linear regularly head‐to‐tail polymers which possess the same chemical regularity as the corresponding tactic polymers, from which they differ only for the lack of steric regularity. A clear interpretation is given of the presence of bands at 1155 and 915 cm.−1 in the IR spectra of isotactic and atactic polypropylenes. The presence of these bands is due to the monomeric unit, with a regular head‐to‐tail arrangement. The absence of these bands in the propylene polymers obtained with the aid of cationic‐type catalysts depends on the presence of a very small content of monomeric units of this type. Finally the conclusion is drawn that the presence of the two above‐mentioned bands in the IR spectrum of the ethylene–propylene copolymers does not indicate the presence of long propylene sequences of the isotactic type, and therefore the existence of a block copolymer, but only the presence of the monomeric unit mentioned above.
X‐ray study of some isotactic substituted poly‐carboalkoxybutadienes
Authors: Natta G. , Corradini P. , Ganis P. 
Published: April 2003

AbstractThe chain conformation and configuration of some polysorbates and poly‐β‐styryl‐acrylates is discussed in this paper. From x‐ray fiber spectra of these polymers we obtained the identity period of 4.80 ± 0.05 A. The conformation of the main chain is the same as that of 1,4 trans polybutadiene and isotactic 1–4 trans polypentadiene. From considerations of the mode of packing of the chains and of the encumbrance of the side groups in respect to the main chain it was possible to assign an erythro configuration in regard to the relative placement of lateral groups. The examined polymers are tritactic and have a trans‐erythro‐isotactic configuration.
Polyamides of 1,4‐cyclohexanebis(methylamine)
Authors: Bell Alan , Smith James G. , Kibler Charles J. 
Published: April 2003

AbstractPolyamides of both cis‐ and trans‐1,4‐cyclohexanebis(methylamine) with aliphatic dicarboxylic acids and copolyamides of trans‐1,4‐cyclohexanebis(methylamine) with p‐xylene‐α,α′‐diamine were prepared in order to discover the effect of cycloalkane rings on melting point. Analogous polyamides of p‐xylene‐α,α′‐diamine were prepared for comparison. The polyamides of trans‐1,4‐cyclohexanebis(methylamine) had higher melting points than the analogous polyamides of p‐xylene‐α,α′‐diamine. This result is believed to be due to the slightly contracted conformation which trans‐1,4‐cyclohexanebis(methylamine) can adopt in the polymer chain. The polyamides of cis‐1,4‐cyclohexanebis(methylamine) melted lower than those of the trans isomer. The lower symmetry of the cis‐diamine accounts for this result. The melting points of the copolyamides of trans‐1,4‐cyclohexanebis(methylamine) and p‐xylene‐α,α′‐diamine were higher than expected. It is suggested that these compositions are examples of partially isomorphous copolyamides.
Influence of the nature of the initiator on the bulk polymerization of methyl methacrylate
Authors: Rafikov S. R. , Gladishev G. P. , Khasanova N. F. , Churbakova N. V. 
Published: April 2003

AbstractThe kinetics of polymerization of MMA activated by ultraviolet irradiation at various temperatures and the polymerization of monomer with dicyclohexylperoxycarbonate have been studied. The activation energy of the polymerization with percarbonate is 14.9 kcal./mole, and that of polymerization with photooxidized monomer is 11.2 kcal./mole. The temperature at which ultraviolet‐oxidation of MMA (0–40°C.) is carried out has no significant influence on the kinetics of polymerization of activated monomer. The gel effect in the case of the dicyclohexylperoxycarbonate‐initiated polymerization of MMA is somewhat greater than that of monomer activated by photooxidation.
Synthesis of trichain and tetrachain radial polybutadienes
Authors: Zelinski R. P. , Wofford C. F. 
Published: April 2003

AbstractTri‐ and tetrachain radial polybutadienes have been synthesized by coupling very dilute solutions of linear polybutadienyllithium with stoichiometric amounts of methyltrichlorosilane or silicon tetrachloride. These polymers have three or four long chains (100–2000 carbon atoms) attached to a single atom.