bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cyclopolymerization. IV. Structure of polymethacrylic anhydride and kinetics of polymerization of methacrylic anhydride
Authors: Smets G. , Hous P. , Deval N. 
Published: April 2003

AbstractThe cyclopolymerization of methacrylic anhydride at 36.6°C. produces a polymer whose structure has been examined by infrared spectrometry and bromometric analysis. This polymer contains mainly hexaatomic rings of the A type (absorption bands at 1800 and 1760 cm.−1) and open anhydride units with unsaturated side‐groups, the content of which varies only slightly with the monomer concentration. Polymerization at 100°C. produces some syndiotactic hexaatomic rings (1730 cm.−1). Chemical analysis of the polymers obtained at 36.6°C. for different monomer concentrations permitted the ratio of the rate constants of vinyl propagation to that of cyclization to be evaluated. This ratio is 0.022 l./mole, compared to 0.17 l./mole for acrylic anhydride. From a plot of the reciprocal of the degree of cyclization against the monomer concentration the values of the ordinate intercepts are interpreted on the basis of chain transfer reaction with monomer and intramolecular isomerization. From a kinetic point of view, the order of reaction at 36.6°C. with respect to the concentration of initiator varies from 0.66 to 0.58 for monomer concentrations of 0.656 and 3.282 mole/l., respectively. With respect to the monomer concentration, the order of reaction is one up to a concentration of 3 mole/l.; above this concentration, the order increases progressively. This behavior can be easily explained by the progressive insolubilization of the polymer and the increasing viscosity of the solution.
Certain characteristics of the polymerization of butadiene‐1,3 in presence of soluble cobalt complex catalyst
Authors: Diaconescu A. I. , Medvedev S. S. 
Published: April 2003

AbstractStudies were carried out on the kinetics of the process for producing 1,4‐cis‐polybutadiene in the presence of the catalytic system formed of monochlordiisobutylaluminum and the alcoholic complex of cobalt chloride. The experiments, carried out in homogenneous benzene solution at room temperature, pointed out the predominant role of water: when water is absent butadiene forms oligomers. Under the given conditions, the rate of polymerization of butadiene increases with the increase in the concentration of cobalt or aluminum compound and varies in a strange way when the water concentration changes. The dependence of the rate of polymerization on water concentration accounts for the difficulties in the reproductibility of experiments. The molecular weights of the polymers obtained increase linearly with the increase in water concentration and decrease with the decrease in the concentration of aluminum or cobalt compound. No dependence was noticed between the microstructure of polymers and the conditions of working.
Single crystals of poly(ethylene terephthalate)
Authors: Yamashita Yuhiko 
Published: April 2003

AbstractSingle crystals of poly(ethylene terephthalate) were prepared by evaporating the solvent slowly from dilute solution at crystallization temperature. The single crystals are parallelograms in shape and thicken by spiral growths with screw dislocations at their center. In the electron microscope they are seen to consist of platelets about 100 A. in thickness. Low‐angle x‐ray measurements on the film obtained by filtering the crystal suspension reveal a long spacing in good agreement with that calculated from shadow lengths. Electron and x‐ray diffraction patterns show that the chain molecules are inclined at about 25–35° to the normal to the basal plane of the single crystals and sharply folded within the lamellae. Various morphological features and arrangement of the unit cell in the single crystal platelets are described and discussed.
Investigation of polyacetaldehyde structure by high resolution nuclear magnetic resonance
Authors: Goodman Murray , Brandrup Johannes 
Published: April 2003

AbstractWe examined the configurations of cationically produced amorphous polyacetaldehyde by high resolution NMR spectroscopy at high temperature in such solvents as dimethylformamide and aniline. Our results show that the polymer backbone is composed of heterotactic and isotactic triad sequences, the former predominating over the latter. Using a 60 Mcycle instrument with or without spin decoupling, we were unable to detect any syndiotactic triad sequences. In addition, the 60 Mcycle NMR spectrum of poly‐α‐deuteroacetaldehyde shows the presence of only the same two stereochemical triads as above. However, examination of polyacetaldehyde with a 100‐Mcycle instrument indicated that a small shoulder exists on the low field side of the heterotactic peak which is probably caused by a small syndiotactic triad content. We used these findings to propose a mechanism for the cationic polymerization of acetaldehyde. We suggest that acetaldehyde may exist in a dimeric form under polymerization conditions leading to a preferred incorporation of mesodimeric units into the propagating chain. Model compound studies involving α,α′‐dimethoxyethyl ether are consistent with this postulate.
Photoyellowing of poly(4,4′‐diphenylolpropane isophthalate): A novel polymer photorearrangement
Authors: Maerov S. B. 
Published: April 2003

AbstractThe photoyellowing of 4,4′‐diphenylolpropane isophthalate (DPP‐I) was attributed to a photochemical rearrangement resulting in a polymer containing o‐hydroxybenzophenones as part of the chain structure. Chain cleavage by photolysis was an accompanying side reaction. o‐Hydroxybenzophenone derivatives of DPP were prepared to serve as model compounds to confirm the structure of the photorearrangement product. Additional confirmation of the mechanism was obtained by solid phase or solution photorearrangement of the model ester, DPP dibenzoate to its monohydroxybenzophenone derivative. Kinetics of the DPP‐I photorearrangement exposed to a xenon high pressure lamp and a carbon are lamp gave rates of 3.9 × 10−2 and 3.8 × 10−3 mole/1.‐hr., respectively. The rate of yellowing in Florida sunlight, open exposure in April, was 1.5 × 10−2 mole/1.‐hr.
Some statistical properties of flexible ring polymers
Authors: Casassa Edward F. 
Published: April 2003

AbstractThe conventional “string‐of‐beads” statistical model for flexible chain polymers is modified for derivation of configurational and thermodynamic properties of long‐chain ring molecules (i.e., flexible linear chains with ends joined) in dilute solution near the Flory temperature. The effect of the intramolecular excluded volume on the meansquare molecular radius is obtained to the first order of approximation; the second virial coefficient is given to the “double contact” approximation; and the angular intensity distribution for Rayleigh scattering is determined for the unperturbed molecule. Qualitatively, all these properties, in comparison to those for linear chains of the same mass, are affected as anticipated from the more compact nature of the ring model.
Localized deformation of lamellar polyethylene crystals
Authors: Reneker D. H. 
Published: April 2003

AbstractThe mechanical and morphological properties of lamellar crystals of polyethylene were studied by deliberately deforming the crystals with a localized strain of known direction and amplitude. In most of the experiments the deformation was achieved by placing the polymer crystals on a thin, brittle, electron‐transparent substrate which was supported by a plastic film. Elongation of the plastic film cracked the brittle substrate, and the polyethylene crystals either broke or were converted into fibers and drawn across the cracks. The breaking and drawing properties of the crystal are related to the orientation of the crystal with respect to the crack and to the intersection of fold domains by the crack. Localized deformation of crystals in suspension by ultrasonic irradiation and by other means is discussed.
Probabilistic considerations of the tacticity of optically active polymers
Authors: Fueno Takayuki , Shelden Ronald A. , Furukawa Junji 
Published: April 2003

AbstractThe probability theory of Markov chains used in the characterization of stereoregular polymers is extended to optically active high polymers. The degree of tacticity is expressed in terms of the transition probabilities for chain growth which is asymmetric with respect to selection of monomer unit configurations. The variation of the Bovey tacticities with the probability parameters is illustrated for the case of asymmetric, simple Markov chains. The relations between tacticity and configurational asymmetry of optically active polymers are discussed.
Aromatic polypyromellitimides from aromatic polyamic acids
Authors: Sroog C. E. , Endrey A. L. , Abramo S. V. , Berr C. E. , Edwards W. M. , Olivier K. L. 
Published: April 2003

AbstractAromatic diamines react with pyromellitic dianhydride in solvents such as dimethyl‐acetamide to form solutions of high molecular weight polyamic acids. These soluble polymers can be converted to insoluble aromatic polyimides. The aromatic polyimides exhibit zero strength temperatures above 700°C. and possess excellent thermal and oxidative stability. The stability characteristics of films and the relation of chemical structure to thermal and hydrolytic stability and to polymer properties such as crystallinity are described.
Base‐catalyzed polymerization of aromatic sulfonamides with an activated double bond. I
Authors: Yoda Naoya , Marvel C. S. 
Published: April 2003

AbstractThe base‐catalyzed polymerization of p‐styrenesulfonamide has given a product with mixed recurring units, some produced by anionic‐initiated vinyl polymerization and some by proton‐transfer polymerization. The products are high softening but yield brittle films. Some preliminary results have been obtained for the polymerization of p‐acryl‐amidobenzenesulfonamide and the related crotonyl and cinnamoyl derivatives. Synthetic methods for the monomers are described.
Polymerization of trioxane by crystallization on activated seeds from cyclohexane solutions
Authors: Morelli F. , Masetti G. , Butta E. , Baccaredda M. 
Published: April 2003

AbstractThe preparation of polyoxymethylene of high molecular weight by polymerization of trioxane, starting from concentrated solutions in hydrocarbon solvents (cyclohexane) initiated by addition of a cationic catalyst (BF3 etherate) and inducing the crystallization of trioxane by cooling the system from the initial to room temperature, is investigated. The success of the method depends largely on the time of permanence of the solution at the initial temperature after the induction period (activation time) the initial solution, which can be controlled by following the temperature variations of the system during this stage. The cooling of the activated solution may be performed either continuously, in which case it may be varied from 15 to 200°C./hr., or in two stages: quenching from the initial temperature to the precipitation point followed by controlled cooling at a lower rate from this point to room temperature. The latter method is preferable when initial temperatures higher than the melting point of the pure trioxane are chosen. Products having inherent viscosities ranging from 2.0 to 3.0 dl./g. (in 0.5% solutions in p‐chlorophenol at 60°C.) are obtained.
Fractionation of polydienes by means of precipitation chromatography
Authors: Poláček J. , Kössler I. , Vodehnal J. 
Published: April 2003

AbstractThe fractionation of polychloroprene, polyisoprene, and polybutadiene was carried out by a modified Baker‐Williams chromatographic precipitation technique. The anomalous decrease of molecular weights of last fractions is explained as a result of oxidation processes leading to formation of peroxide bonds in the polymer. A correlation between the CO group content and the value of the constant, k′, of the Schulz‐Blaschke equation was found. The advantage of maintaining a relatively low temperature during the precipitation process and the influence of the method of preparation of the polymer film on the molecular weight distribution curve has been demonstrated.
Electron spin resonance of heat‐treated poly(vinyl chloride)
Authors: Ouchi Isuke 
Published: April 2003

AbstractPoly(vinyl chloride) was heat‐treated, in most cases below 400°C., either in air or in a vacuum and examined by ESR by means of a spectrometer with modified microwave circuit. The ESR signals are first observed at an early stage of degradation and increase with heating time. In the case of heat treatment in a vacuum, the ESR stops increasing when dehydrochlorination is nearly finished, while in the case of the treatment in air, the signal continues to increase after dehydrochlorination is finished. The effects of oxygen and the saturation characteristics of the ESR are quite different for the chars heat‐treated below 400°C. and those heat‐treated above 400°C. Below 400°C., the signal shows strong saturation in a vacuum but not in air. Oxygen easily affects the signal, shortening the spin‐lattice relaxation time. For the char treated above 400°C., the signal does not saturate as strongly and is quenched by oxygen.
Absorption spectra of poly‐p‐iodostyrene
Authors: Luongo J. P. , Salovey R. 
Published: April 2003

AbstractFrom the infrared and ultraviolet spectra of iodinated polystyrene, the location and amount of the iodine substitution in the polystyrene molecule can be determined. In addition, when isotactic polystyrene is iodinated, the tacticity is retained but the helical conformation of the carbon backbone, both in solution and in the solid state, has been modified. Comparison of the atactic, helical isotactic, and nonhelical iodinated isotactic spectra show that bands at 1297, 585, and 558 cm.−1 and particularly the 1080/1055 cm.−1 doublet can be attributed to the helical conformation of the carbon backbone of isotactic polystyrene.
Epoxide–alcohol reaction catalyzed by boron trifluoride. Part I. Phenyl glycidyl ether–alcohol reaction in dioxane
Authors: Lee Lieng‐Huang , Pankey John W. , Heeschen J. P. 
Published: April 2003

AbstractPhenyl glycidyl ether, a model compound for bisphenol‐A type epoxy resins, was reacted with alcohols in dioxane in the presence of boron trifluoride etherate. For isobutyl, sec‐butyl, and n‐butyl alcohols the reaction paths were similar and found to be: (1) epoxide–alcohol 1:1 addition, (2) epoxide–alcohol–dioxane addition, and (3) homopolymerization of the expoxide. With excess alcohol, homopolymerization could be minimized. In all cases, the predominant 1:1 adduct was shown to be 1‐butoxy‐3‐phenoxy‐2‐propanol. There was indication that a small amount of the 1:1 adduct containing primary hydroxyl group was formed also. With tert‐butyl alcohol, 3‐phenoxy‐1,2‐propanediol was obtained as well. With phenol, the main reaction was homopolymerization of phenyl glycidyl ether.
Critical conditions for formation of infinite networks in branched‐chain polymers
Authors: Tanaka Yoshio , Kakiuchi Hiroshi 
Published: April 2003

AbstractThe conditions necessary for infinite network formation due to the bifunctional inter‐unit junction were reinvestigated, and the difference in theories between Flory and Case or Kahn was mentioned. The theory is extended to a more general case than those of Flory and of Case or Kahn. It also deals with the critical point in the condensation reaction between mixtures of two types of functional groups containing one or more functionalities. It is shown that at the critical point,
\documentclass{article}\pagestyle{empty}\begin{document}$ P_A P_B \left( {1 - \rho _1 } \right)\left( {1 - \sigma _1 } \right)\sum\limits_{}^n {_{\rho i} \left( {fi - 1} \right)} \sum\limits_{}^n {_{\sigma i} \left( {gi - 1} \right)} = 1 $\end{document}
and/or
\documentclass{article}\pagestyle{empty}\begin{document}$ \left[ {{1 \mathord{\left/ {\vphantom {1 {\left( {1 + r} \right)}}} \right. \kern-\nulldelimiterspace} {\left( {1 + r} \right)}}} \right]\left[ {rP_A \sum\limits_{}^n {_{\sigma i} \left( {gi - 1} \right) + P_B \sum\limits_{}^n {_{\rho i} \left( {fi - 1} \right)} } } \right] = 1$\end{document}
where PA and PB are the respective probabilities that an A or B group has reacted, fi and gi are the functionalities of Ai and Bi monomers, r is the ratio of A groups to B groups at the initial state, and ρi, σi, are the molar fractions of Ai and Bi, respectively.
Crystallization in stretched polymer networks. I. trans‐polychloroprene
Authors: Gent A. N. 
Published: April 2003

AbstractMeasurements are described of the rates of crystallization of uncrosslinked trans‐polychloroprene over a range of temperature and of three crosslinked samples over a wide range of extension and temperature. The large increases in rate with extension are attributed to corresponding increases in the equilibrium melting temperature and hence degree of supercooling. The rise in melting temperature has been measured and is found (1) to account satisfactorily for the observed changes in rate, and (2) to be in good agreement with Flory's treatment of oriented crystallization in stretched networks. The form and magnitude of the changes in tensile stress are also in accord with the formation of oriented crystallites, and seem incompatible with folded‐chain crystallization. When reduced to a condition of constant segmental mobility, the rates of crystallization are shown to follow a common dependence upon the degree of supercooling. This relation is compared with the predictions of nucleation theory.
Dilute solution properties of high molecular weight poly(isobutyl methacrylate). II. Light scattering
Authors: Valles Richard J. 
Published: April 2003

AbstractA high molecular weight linear sample of poly(isobutyl methacrylate) was fractionated from an acetone–methanol mixture. An adaptation on a Brice‐Phoenix photometer made it possible to run light‐scattering measurements at angles of 15, 20, and 25°, in addition to the usual angles. The addition of the low angles made the angular extrapolations more accurate. The parameters in the Mark‐Houwink equation are reported at several temperatures. The molecular weight range studied was 3 × 106 to 11 × 106.
Study of hydrogen bonding in poly(vinyl alcohol) by a nuclear magnetic resonance method
Authors: Gupta Ramdas P. , Laible Roy C. 
Published: April 2003

AbstractThe effect of water fixation in poly(vinyl alcohol) yarn has been studied by the NMR method. Water content in the PVA specimen was varied by exposing the specimen to different relative humidity conditions. The NMR wide line spectra have been registered for samples of PVA (a) dried at 80°C. for 24 hr., (b) conditioned to 40% relative humidity, and (c) conditioned to 80% relative humidity. Wide line spectra for the dry specimen of PVA have a broad band only, but the 40% relative humidity conditioned sample has a broad band and a narrow band, and at the same time the sample conditioned to 80% relative humidity has a broad band and two narrow bands. Variation of intensity as a function of water content has been studied. Variation of wide and narrow band intensity shows that at low relative humidity water enters the amorphous and crystalline regions and is held there by the formation of hydrogen bonds. Hydroxyl groups may replace hydrogen atoms at random on a carbon chain without destroying crystallinity. In the amorphous regions water molecules are held relatively free and are accommodated in voids. This would then account for the second peak in the narrow band of the spectrum seen at higher water contents.
Crystal structure of hexagonal polyselenomethylene
Authors: Carazzolo G. , Valle G. 
Published: April 2003

AbstractThe crystal structure of hexagonal polyselenomethylene is described. It has a hexagonal unit cell with a = 5.22 A. and c = 46.25 A. The polymer chains are helices with the helix axis parallel to c. In the identity period of 46.25 A., there are 21 CH2Se units and 11 turns of the helix. The crystal structures of polyoxymethylene, polythiomethylene, and polyselenomethylene are compared.
Ringed spherulite deformation and multiple‐order light scattering from ringed spherulites
Authors: Moore Robert S. 
Published: April 2003

AbstractFilms of low molecular weight linear (LMWL) polyethylene, low molecular weight poly(ethylene adipate), and medium molecular weight linear (MMWL) polyethylene, all of which contained ringed spherulites, were studied by photographic light scattering and by photomicroscopy. The wide‐angle crossed polarizer scattering pattern was observed to consist of a set of arcs if the sample contained uniform well ordered rings, while a diffuse circle was observed as a scattering pattern if the sample contained poorly ordered rings. The first known multiple‐order crossed and parallel polarizer scattering patterns were obtained from samples of LMWL polyethylene and samples of poly(ethylene adipate). Such scattering patterns were not predicted by the theory of Stein and Rhodes for scattering from ringed spherulites. Analysis of these patterns indicates that they are second‐ and third‐order scattering patterns characteristic of the ring spacing. The angular positions of the maxima can be predicted by a generalization of the equation for first‐order ring scattering. The technique of photographic light scattering was also used to study the deformation of ringed spherulites in films of MMWL polyethylene. Results of the light‐scattering measurements indicate that accompanying spherulite deformation there is an increase in the twist distance (and, hence, the ring spacing) of those spherulite fibrils in the direction of tensile stress, and a decrease in the twist distance of those fibrils at right angles to the stress direction. The data are presented and discussed in terms of current theories of spherulite deformation.
Internal motion in organosilicon polymers. I. Linear dimethylpolysilazane
Authors: Model F. S. , Redl G. , Rochow E. G. 
Published: April 2003

AbstractA linear dimethylpolysilazane polymer has been prepared and its internal motion studied by the techniques of broadline nuclear magnetic resonance. Second moments and line widths are reported as a function of temperature from −196 to 30°C. The results are compared to those for linear dimethylpolysiloxane, as well as to those for the crosslinked siloxane and silazane. The experimental low‐temperature second moment of 7.25 ± 0.5 gauss2 corresponds to a C3 reorientation of methyl groups about the silicon–carbon bond. The motions occurring in the silazane are found to be the same as those in the corresponding siloxane. The transition to low second moments occurs approximately 30°C. higher in the linear silazane than in the linear siloxane. This is attributed to a somewhat greater resistance to motion in the silazane.
γ‐irradiation of siloxane polymers in air and vacuum at several temperatures
Authors: Jenkins Robert 
Published: April 2003

AbstractThe effects of γ‐irradiation on two polysiloxanes in environments of air and vacuum at several selected temperatures were studied. The physical property monitored during the γ‐irradiation of the two polysiloxanes was the change in dynamic modulus which, in turn, is proportional to the change in the number of elastically effective chains in the polymer network. The measurements were accomplished by recording in situ the freeend response of the polymeric cantilever reeds in forced resonance at and near their fundamental frequency of resonance. The apparent energy of activation of crosslinking for the polydimethylsiloxane polymer was found to be 0.56 kcal./mole in vacuum over a limited temperature range, and 3.5 kcal./mole in air. For the polydimethyl‐diphenylsiloxane polymer, the apparent energy of activation was found to be about 1.3 kcal./mole in vacuum, whereas in air the polymer response was complex, displaying both scissioning and crosslinking reactions so that a value could not be obtained. The ability of the pendant phenyl groups to reduce the effective crosslinking rate was found to be sensitive to both temperature and environment.