bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of α,ω‐difunctional polystyrene and its reaction with diisocyanates
Authors: Shimura Yukio 
Published: June 2010

Abstractα,ω‐Dihydroxyl polystyrene was synthesized by anionic polymerization of styrene, followed by the addition of ethylene oxide. The polymerization was carried out either in tetrahydrofuran or in dioxane, with alkali metal complex of naphthalene, biphenyl, or α‐methyl styrene. The molecular weight of the hydroxyl‐ended polystyrene obtained ranged from 800 to 12,000. Polyurethanes were obtained by treating the polystyrene with diisocyanates such as tetramethylene‐, p‐phenylene‐, 1,5‐naphthalene‐, and diphenylmethane‐diisocyanate. Molecular weight increase due to the polyurethane formation varied with the condition, but some of the resulting polymers showed increases of more than thirty times that of the initial polystyrene.
Synthesis of block polymers by homogeneous anionic polymerization
Authors: Fetters L. J. 
Published: June 2010

AbstractThe advent of the homogeneous, termination‐free anionic polymerization systems has proven to be a valuable synthesis tool for the polymer scientist. The absence of a spontaneous termination reaction in these systems makes it feasible to form a variety of interesting polymeric materials, i.e., linear, block polymers, star‐shaped polymers, and well‐defined graft polymers, as well as chains garnished at the end (or ends) with reactive groups. Recently linear block polymers of styrene and butadiene have achieved commercial importance. This review covers the synthesis methods of these block polymers and touches briefly on the formation of other block polymers by diverse synthesis routes.
Effect of sequential arrangements on block copolymer properties
Authors: Ceresa R. J. 
Published: June 2010

AbstractThe solution, melt, and solid–state properties of a range of block co‐polymers are considered in relation to the sequential arrangement within the macromolecule. An attempt is made to predict block copolymer properties from a knowledge of the homopolymer or sequence copolymer properties. The application properties of industrial systems are then reviewed in the light of the hypotheses.
Rhodium‐catalyzed emulsion polymerization of butadiene
Authors: Morton Maurice , Das B. 
Published: June 2010

AbstractRecent work has shown that rhodium salts in aqueous solution are capable of polymerizing butadiene to a high trans‐1,4 polymer, especially in the presence of certain surfactants of the sulfate or sulfonate types, which act as ligands for the rhodium. It has now been confirmed that the effective surfactants are of two types: sodium lauryl sulfate and the sodium alkyl benzene sulfonates having alkyl chains greater than C5. Studies of these systems have also been conducted in homogeneous solution, in an attempt to elucidate the mechanism. For this purpose, solvents such as tetrahydrofuran, dimethoxyethane, and the dimethyl ester of ethylene glycol were found to be effective. However, the polymerization rate was much slower than in the heterogeneous aqueous systems and also appeared to be independent of the presence of the surfactant. This phenomenon was apparently due to the fact that these solvents also act as ligands for the rhodium, thus giving rise to catalyst complexes which are less effective in polymerization.
Kinetic study on the alkaline degradation of amylose
Authors: Lai Yuan‐Zong , Sarkanen K. V. 
Published: June 2010

AbstractThe kinetics of end‐wise degradation of amylose has been studied varying base concentration and temperature. At 100°C, the rate of peeling increases with hydroxyl ion concentration up to 0.1 N base concentration, remaining constant thereafter, whereas the rate of termination continues to increase beyond this point levelling off finally to a constant value at approximately 1.5 N base concentration. As a consequence, the ratio of peeling to termination is sufficiently high in 0.01–0.1 N sodium hydroxide solutions to effect total degradation of amylose. The kinetic pattern is interpreted in terms of mono‐ and di‐ions of the reducing end‐groups acting as reactive intermediates. The potential application of the peeling reaction to structural studies of polysaccharides is discussed.
Light scattering by cellulose. I. Native cellulose films
Authors: Borch J. , Marchessault R. H. 
Published: June 2010

AbstractCrystalline cellulose films are analyzed by solid‐state light scattering, using a photographic technique. The light‐scattering envelopes may be theoretically predicted by assuming a model consisting of randomly oriented anisotropic rods. The experimentally observed anisotropy patterns are discussed in terms of this model and are related to various ways in which the fibrils may aggregate. These are often visible in electron micrographs of cellulose materials. The method is applicable to paper samples which are sufficiently thin and dense.
Photoconducting pyrrone polymers
Authors: Reucroft P. J. , Scott H. , Serafin F. L. 
Published: June 2010

AbstractPyrrone polymers are found to exhibit substantial photoconductivity, photocurrent‐dark current ratios of up to 300 being obtained with incident intensities of polychromatic light of 10–20 m.w./cm2. The condensation product obtained from 3,3′, 4,4′‐benzophenone tetracarboxylic dianhydride and 3,3′, ‐diaminobenzidine (BTDA‐DAB) is about 4 to 5 times more photoresponsive than the product obtained from pyromellitic dianhydride and the same diamine (PMDA‐DAB). Maximum photoresponese in obtained when samples are cured for at least 24 hours at 300°C. A linear dependence of photocurrent on voltage is found in the range 102 to 105 volts/cm. The temperature dependence of photocurrent indicates that photocarriers: are produced by more than one mechanism in the temperature range from room temperature to 300°C. Photoresponse is found to be maximum in the ultraviolet‐visible region, with a peak response at 610 mμ for PMDA‐DAB and 550 mμ for BTDA‐DAB.
Relationships among melt flow, glass transition temperature, and inherent viscosity of thermoplastic polyesters
Authors: Combs R. L. , Nations R. G. 
Published: June 2010

AbstractThe melt flow (MF) (an inverse function of melt viscosity) for a wide variety of polyesters has been related in one equation to their glass transition temperatures (Tg), their inherent viscosities, and their melt temperatures. This empirical equation was developed by regression methods on various relationships. Although it contains only three constants, it gives a good fit of the data. Such an equation allows prediction of the processability of a polyester providing its Tg and its inherent viscosity are known. Only a small amount of sample is required for these two measurements. The form of this equation presents an interesting speculation: perhaps there is a constant ratio of the energy of activation for viscous flow at constant shear rate to the Tg.
Rapid determination of crosslink densities and interaction parameters from swelling rate data
Authors: Schreiber H. P. , Holden H. W. , Barna G. 
Published: June 2010

AbstractGravimetric determinations of weight gain were carried out for ethylene‐propylene elstomer (EPR) samples crosslinked by dicumyl peroxide and immersed for periods up to IS minutes in various swelling solvents. The weight gain data were analyzed on the assumed existence of a power‐law relationship with immersion time as well as the more usual assumption that the swelling rate is diffusion‐controlled. The former analysis led to strong correlations between initial swelling rates and the Flory‐Huggins interaction parameter of a polymer‐solvent pair. The latter analysis correlated initial uptake rates with crosslink densities obtained from equilibrium swelling results. Initial uptake rates were used to estimate the interaction parameter for the system EPR‐tetrahydronaphthalene, and to measure the effect of rutile and carbon black filler on the cross‐linking process. Rutile behaved as an inert filler, but results for carbon black proved anomalous, indicating need for further study.
The determination of the molecular weight and molecular weight distribution of dehydrogenase polymers of coniferyl alcohol and lignins
Authors: Soundararajan T. N. , Wayman Morris 
Published: June 2010

AbstractThis paper describes experiments aimed at the development of a convenient method of determining the molecular weight and the molecular weight distribution of lignins and lignin‐like polymers. As a model, a polymer of coniferyl alcohol prepared by enzymatic dehydrogenation was fractionated on columns of Sephadex G 75, G 100 and a mixture of G 75, G 100 and G 200 of equal volumes swollen in dimethyl sulphoxide. The columns were calibrated by means of sharp fractions obtained by preparative fractionation characterized independently by sedimentation equilibrium ultracentrifugation. From the elution curve of the sample and the calibration curve the molecular weight and its distribution were calculated. The assumption that the system predicts the molecular weight and its distribution correctly was tested by running a sample whose molecular weight distribution was known by ultracentrifugation. The distribution calculated from the gel column chromatograph was found to coincide with that obtained by ultracentrifugation. The molecular weights and their distributions obtained on milled wood lignin samples by this method appear to be reasonable.
Relation of glass transition temperature to molecular structure of addition copolymers
Authors: Barton John M. 
Published: June 2010

AbstractAn equation is proposed relating the glass transition temperature (TG) of copolymers to their molecular structure in terms of the mole fractions of the various diad sequences of monomer units combined in the copolymer chain, and temperature parameters (Tij) characteristic of each type of sequence, ij. The equation, an extension of the Gibbs and DiMarzio copolymer TG theory, accounts for the effect on TG of the different types of bonds between repeating units in different diad sequences, and is in its general form: \documentclass{article}\pagestyle{empty}\begin{document}$ T_G = \sum\limits_{i,j} {n'_{ij}} T_{ij} $\end{document}. In a binary copolymer of structure [(a) × (b)y] n, corresponding to the ij sequences ‐aa‐, ‐ba‐, ‐ab‐, and ‐bb‐. The term n'ij is the mole fraction of ij sequences, nij weighted according to the number of rotatable bonds per sequence, αij, and \documentclass{article}\pagestyle{empty}\begin{document}$ n_{ij} = n_{ij} \alpha ij/\sum\limits_{i,j} {\left({n_{ij} \alpha _{ij}} \right)} $\end{document}. The variation in the distribution of sequences with overall composition is obtained from the copolymerization reactivity ratios. The theory, which quantitatively describes the sometimes observed maximum or minimum in TG ‐ composition plots, gives good agreement with published data for 11 copolymer systems. Application of the theory to give homopolymer TG's by extrapolation is demonstrated. Inter‐relations are found with other published theories of copolymer TG.
The circular dichroism of polynucleotides in relation to their conformations
Authors: Imahori Kazutomo , Watanabe Kimitsuna 
Published: June 2010

AbstractThe circular dichroism of polynucleotide or oligonucleotides reflects their conformations. The CD spectra of oligonucleotides vary depending upon the species of bases involved and their sequence. The amplitude of CD peak is proportional to the degree of stacking and furnishes the way to estimate some thermodynamic parameters of stacking. The CD spectrum of poly (G + C) or poly (A + U) is close to the graphical summation of its constituent homopolymers, except blue shift of the peaks, and decrease in their amplitudes. Double stranded copolymer, poly (A ‐ U) or poly (G ‐ C) has a quite different feature from that of poly (A + U) or poly (G + C), reflecting the difference in mode of base stacking. The CD spectrum of poly dAT is quite different from poly (A ‐ U) and DNA has a different CD pattern from RNA. These differences can be interpreted by the difference in the geometry of the bases. The peak position of CD spectrum of double stranded RNA varied depending on the ratio of (G ‐ C)/(A ‐ U). Thus it is possible to estimate (G ‐ C) or (A ‐ U) content by analyzing the CD spectrum. The CD spectra of tRNA are different depending on the species of it. It is of greatest interest that Met‐tRNAF has quite different CD pattern from Met‐tRNAM. This can be interpreted by the difference in the number of G ‐ C or A ‐ U pairs between them. A remarkable change in CD spectrum was observed when poly dAT is complexed with RNA polymerase or when aminoacyl RNA is complexed with T factor. The conformational change suggested by CD will play an important role for the elucidation of reaction mechanism.
Studies in the polymerization of methyl methacrylate with VCl4‐Al (C2H5)3 catalyst system in acetonitrile
Authors: Dixit Sunit S. , Deshpande A. B. , Kapur S. L. 
Published: June 2010

AbstractMethyl methacrylate has been polymerized at 40°C with VCl4‐AlEt3 catalyst system in acetonitrile. A linear dependence of rate of polymerization on the monomer and catalyst concentrations as well as overall activation energy of 10.96 kcal/mole exhibits coordinated anionic mechanism. However, characterization of the structure of the polymer by NMR spectra revealed the presence of heterotactic units, whereas on the addition of hydro‐quinone to the catalyst system, the polymer obtained was a stereoblock. The mechanism of polymerization is discussed in the light of the kinetic studies and the structure of PMMA.
relation between the polymer conformation and the elastic modulus of the crystalline region of polymer
Authors: Sakurada Ichiro , Kaji Keisuke 
Published: June 2010

AbstractThe force required to stretch a polymer chain by 1% (f value) was calculated from experimental values of elastic moduli E1 in the direction of molecular axis and the cross‐sectional area of the molecule of 25 well known polymers. The f value is mainly dependent on the conformation of a molecule and almost independent of side groups. The f values of polymers of various types of conformation may be summarized as follows: T type, 4−5 × 10−5 dyne; TGTG type, 1.5 × 10−5 dyne; TG(3/1) type, 1 × 10−5 dyne; T′G′ (7/2) type, 0.58 × 10−5 dyne; T′G′ (4/1) type, 0.36 × 10−5 dyne; TTGG type, 0.29 × 10−5 dyne; where T, G, and G mean trans, gauche and minus gauche, respectively, and the numbers in the parentheses denote helical structures. The reason for an anomalous apparent E1 value of nylon 6 (α‐form) previously reported was elucidated; it was confirmed that E1 exhibits a value expected for a polymer with a nearly extended zigzag conformation.
Poly(ethylene sulfide). I. Unique seed polymerization technique‐growth of “immortal” polymer
Authors: Gobran Riad H. , Larsen Roy 
Published: June 2010

AbstractPoly(ethylene sulfide) was prepared by a unique two‐step polymerization technique in which a “seed polymer” was initially formed, compacted to a desired bulk density, and then used to polymerize fresh ethylene sulfide monomer. The seed polymer was prepared by reacting ethylene sulfide with diethylzinc‐water in a suitable solvent. The final polymer was an exact magnification that faithfully reproduced any shape of seed used with regard to relative dimensions, angularities, curvatures and even imperfections. Poly(ethylene sulfide) prepared by this process can be used for successive polymerizations that proceed at the same rate as the original seed with comparable zinc content, and thus behaves as an “immortal” polymer. The high molecular weight polymer melts above 200°C, is highly crystalline, and is, insoluble in most organic solvents at ordinary temperatures. A number of solvents dissolve the polymer above 140°C at which temperature thermal degradation takes place. When the polymer is stabilized by use of certain thermal stabilizers, it can be successfully molded to give excellent physical and mechanical properties.
Some effects on polycondensation reactions
Authors: Ogata Naoya 
Published: June 2010

AbstractThe effect of solvents or chelating agents on polycondensation reactions was investigated. Solution polycondensation of nylon 66 salt was enhanced in ketone solvents such as methyl acetophenone or diisobutyl ketone, a polyamide of high molecular weight being formed. Room‐temperature polycondensation of N‐(hydroxyethyl)‐β‐alanine ester or 4‐thio‐e‐aminocaproate was influenced by solvents and chelating agents with functional groups, and the rate or the equilibrium of the reaction were apparently changed. Interfacial polycondensation of m‐phenylenediamine and isophthaloyl chloride yielded aromatic polyamide having a high molecular weight in ketone solvents such as cyclohexanone or methyl acetophenone. It was found that isophthaloyl chloride reacted slowly with cyclohexanone to yield quantitatively isophthalic acid. These effects of solvents or chelating reagents on polycondensation reactions might be attributed to the reactivity change of functional group during polycondensation reactions.
Small‐angle and wide‐angle X‐ray investigations on poly‐m‐bromostyrene and poly‐o‐bromostyrene in benzene solution
Authors: Durchschlag H. , Puchwein G. , Kratky O. , Breitenbach J. W. , Olaj O. F. 
Published: June 2010

AbstractVarious fractions of poly‐m‐bromostyrene and poly‐o‐bromostyrene in benzene were studied by the small‐angle and wide‐angle x‐ray methods. The combination of the two methods makes it possible to supply information on short‐range order and long‐range order in the same molecule. Four fractions of poly‐m‐bromostyrene of the approximate ratio of the degrees of polymerization (1:2:3:4) were studied. The molecular weight was determined from the absolute intensity of the small‐angle scattering at zero angle and the radius of gyration from the slope in the Guinier plot. The concentration dependence of both figures is discussed. The determination of the persistence length is not directly possible but results after elimination of the cross‐section factor (a = 17.3 Å). It is on the average about 20% smaller than the value calculated from the hydrodynamic length L and the radius of gyration Rexp supposing a Gauss coil, which can be explained by polydispersity and by the fact that benzene does not represent a Θ‐solvent but is better than this. The scattering curves of poly‐m‐bromostyrene solution and of a solution of m‐bromotoluene containing the same number of bromine atoms show no difference in the exactly measured wide‐angle field, which indicates that with the polymer product the distances between the bromine atoms are irregular. With poly‐o‐bromostyrene two possibilities of subtraction of a blank solution were compared. The small‐angle investigations of poly‐o‐bromostyrene permitted the determination of the molecular weight, radius of gyration, persistence length, radius of gyration of the cross section, mass per unit length, and hydrodynamic length. The high mass covering per unit length (Mq ≃ 90–100/Å), the large radius of gyration of the cross‐section (Rq ≃ 4.4 Å), and the large radius of the cross‐section, obtained in three independent ways (rq ≃ 6 Å) afford indications for the appearance of helical ranges in solution. A further support for this is the discovery of a definite interbromine spacing (l = 4.6 Å) by wide‐angle studies. This can only be explained by order of the bromine atoms over a certain range. On the other hand the presence of large coil ranges is shown by the direct determinability of the persistence length (a = 16.5 Å) from the transition point in the plot of I (2θ)2 against (2θ) as well by the not too great deviation from the Gaussian statistic of the coil. The most plausible explanation of all findings with poly‐o‐bromostyrene is that helical and coil ranges coexist in solution. The helical zones will, however, not extend over any too great range, so that the general impression of a wormlike chain remains. The verification of the procedure of interferometric measurement of defined spacings of heavy atoms in molecules is made with the example of the 2,5‐dibromotoluene by remeasurement of the known interbromine spacing.
Failure surfaces in principal stress space
Authors: Tschoegl N. W. 
Published: June 2010

AbstractCriteria for failure in multiaxial states of stress have associated with them geometrical representations as surfaces in principal stress space. Any combination of stresses is safe if the corresponding point in principal stress space falls within the failure surface. The material will fail if the point lies on or outside of the surface. The geometry of some simple surfaces and means for determining them on isotropic bodies are discussed, and the scanty information on failure surfaces for polymeric materials is reviewed.
Friedel‐crafts and related reactions on poly(vinyl chloride)
Authors: Hace D. , Bravar M. 
Published: June 2010

AbstractPolyvinyl chloride solubilized in an appropriate solvent can be transformed to a complex mixture of chemical compounds by treating it with aromatics in the presence of Friedel‐Crafts catalysts.The primary reaction is the alkylation of aromatics with polyvinyl chloride; it is followed by other parallel and secondary reactions, viz., intramolecular cyclizations of alkylated products and a cleavage of molecules to fragments of lower molecular weight. All this is accompanied by the process of hydrogen chloride elimination from the reacting polymer. The chlorinated hydrocarbons, when used as solvents can also take part in reactions, leading to the crosslinking of polymers.An earlier work of Belgian authors (Teyssié, Smets) was continued in order to elucidate further the complex of the reactions mentioned above. A number of Friedel‐Crafts condensations were carried out using polyvinyl chloride to alkylate benzene and toluene in various solvents, such as 1,2‐dichloroethane, cyclohexanone, trichloroethane and tetrahydrofurane in the presence of AlCl3 and BF3 as catalysts. The kinetic curves representing the dehydrochlorination process were obtained, allowing the interpretations of the mechanisms involved. The products thus obtained were characterized by physical and chemical means. The significant peaks in IR‐spectra which would account for the intramolecular cyclizations and branching of macromolecular chains were also observed.
Measurement of interfacial and surface tensions in polymer systems
Authors: Patterson H. T. , Hu K. H. , Grindstaff T. H. 
Published: June 2010

AbstractPrincen's modification of Vonnegut's rotating drop procedure for measuring inter‐facial tension between low viscosity liquids has been adapted for use with pairs of liquid polymers with viscosities up to 5000 poise. Extrapolation to infinite time of results obtained with 10–20 min of rotation provided steady state data as indicated by its corre‐spondence with results reported from other techniques. An adaptation of this procedure was also found useful for determining surface tension values of molten polymers at temperatures up to 290°C. Reductions of 60–70% in interfacial tension between viscous samples of a polydimethylsiloxane and a copolyether were accomplished by addition of 1–2% of amphi‐pathic or polar compounds such as polydimethylsiloxane‐polyoxyethylene copolymers and carboxyl‐substituted polydimethylsiloxanes. A linear reduction in interfacial tension with a logarithmic increase of additive concentration was noted.