bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystallization and dissolution temperatures of poly(vinyl alcohol) crystal lamellae
Authors: Kenney J. F. , Holland V. F. 
Published: April 2003

AbstractPoly(vinyl alcohol) single crystal platelets having a stepheight of approximately 100 A. were obtained by isothermal crystallization from dilute triethylene glycol solution. Material crystallized at temperature Tc redissolved in the same solvent at a higher temperature Ts. A plot of Tc versus Ts gave a straight line of slope 0.47. Extrapolation of this line to Tc = Ts gave (Tm)∞, which may be regarded as the dissolution temperature of the crystal of infinite stepheight. (Tm)∞ for this sample in triethylene glycol was 220°C. The crystalline nature of the platelets was established by electron and x‐ray diffraction techniques. A total of three Bragg d spacings having the values of 3.9, 4.4, and 4.6 A. (±0.05 A.) were measured. These spacings were indexed as the (200), (101), and (101) reflections, respectively, of the monoclinic unit cell of Bunn. The x‐ray diffractogram exhibits sharp intensities of the (101) and (101) reflections. The crystallinity calculated from the density of the poly(vinyl alcohol) precipitated from dilute solutions in triethylene glycol was 42%. Although the overall degree of crystalline perfection of this poly(vinyl alcohol) is low, the linear relationship between Ts and Tc and the formation of definite shaped single crystals when crystallized from dilute solution suggest that poly(vinyl alcohol) crystallizes in the same manner as other semicrystalline polymers.
Polyoxazolidones prepared from bisurethans and bisepoxides
Authors: Iwakura Yoshio , Izawa Shin‐Ichi , Hayano Fusakazu 
Published: April 2003

AbstractLinear polymers containing oxazolidone rings in the main chain were prepared from difunctional urethans and epoxides by the synthetic method previously used for reaction of monofunctional urethans and epoxides. The similarity of the infrared spectra of polymers and model compounds, bisoxazolidones, showed the presence of oxazolidone rings in a polymer chain. The solubility and softening temperatures of the polymers varied with the urethan unit but not with the bisepoxide structure. Polymers prepared from p‐phenylenedimethylurethan and variable bisepoxides were insoluble or partially soluble in dimethylformamide, dimethyl sulfoxide, and m‐cresol and had higher softening temperatures. Polymers from m‐phenylenediethylurethan or toluenediethylurethan and bisepoxides were soluble in the organic solvents mentioned above, and had lower softening temperatures.
Enhanced x‐ray diffraction patterns from oriented fibers
Authors: Milberg M. E. 
Published: April 2003

AbstractThe difference x‐ray diffraction pattern can reveal the presence of oriented, ordered material whose conventional diffraction pattern is masked by that of unoriented, disordered material. It is shown that this enhancement results from the fact that scattering from only oriented material contributes to the difference intensity, defined as the difference between the scattered intensity and its average over the polar angle in intensity space. Difference patterns of lightly crosslinked natural rubber, obtained as a function of elongation, show the development of crystallinity at smaller elongations than do the corresponding conventional patterns and indicate that nearly all the oriented material is crystalline. The difference and conventional patterns were obtained from the same diffractometer data. Photographically recorded diffraction patterns are intermediate between the conventional and difference diffractometer patterns in sensitivity to crystallinity. The difference diffraction pattern of a highly oriented atactic polystyrene fiber shows no evidence of crystallinity, the halos on the difference pattern being just as broad as those on the conventional pattern with no apparent tendency to break up into crystalline lines.
Alternating copolymerization of ethylene with maleic anhydride
Authors: Machi Sueo , Sakai Takashi , Gotoda Masao , Kagiya Tsutomu 
Published: April 2003

AbstractThe copolymerization of ethylene with maleic anhydride was carried out with γ‐radiation and a radical initiator, i.e., 2,2′‐azobisisobutyronitrile and diisopropyl peroxydicarbonate under pressure at various reaction conditions. The homopolymerization of neither monomer was observed in this system. In the γ‐ray‐initiated copolymerization the G value (polymerized monomer molecules per 100 e.v.) was shown to be between 103 and 104. It was found that the dose rate exponent of the rate is approximately unity, and the rate is proportional to the amount of ethylene monomer. Apparent activation energies of 1.8 and 27.5 kcal./mole were obtained for γ‐ray‐initiated and AIBN‐initiated copolymerization, respectively. Since the composition of copolymer is independent of monomer molar ratio and the molar ratio of ethylene to maleic anhydride in the polymer is approximately unity, the monomer reactivity ratios were obtained as rE ≃ 0 and rM ≃ 0 for γ‐ray‐initiated polymerization at 40°C. Alternating copolymerization was, therefore, concluded to occur. Infrared analysis of the copolymer is almost consistent with this. The copolymer in the solid state is amorphous. It is soluble in water, cyclohexane, and dimethylformamide and insoluble in lower alcohols, ether, and aromatic hydrocarbons. The aqueous solution of polymer gave a strong acid.
Chain transfer in ethylene polymerization
Authors: Mortimer George A. 
Published: April 2003

AbstractChain transfer constants in the homogeneous free‐radical polymerization of ethylene at 1360 atm. and 130°C. have been determined for over 50 compounds, including nearly 300 hydrocarbons. The effects of substitution, unsaturation, and ring strain in the transfer agent molecule on the reactivity of its CH bonds in chain‐transfer reactions with a polyethylene growing chain are analyzed. Qualitatively, these trends parallel those found for simple radicals attacking simple molecules. However, the principle that the reactivity of a compound is the sum of the reactivities of all reactive bonds, which is well established for simple radicals and transfer agents, is found not to be true in ethylene polymerization. It is postulated that the deviations from this principle are due to steric factors which become very important when the free radical is bulky. The transfer constants measured in ethylene polymerization are also compared with transfer constants in other systems. A strong correlation is found between the transfer constants in ethylene and published data on rates of abstraction of hydrogen atoms by methyl radicals.
Studies on some radical transfer reactions. Part I. Hydrogen atom abstraction from some organic substrates by ȮH radicals
Authors: Mitra Bhairab Chandra , Chadha Subhash Chander , Ghosh Premamoy , Palit Santi R. 
Published: April 2003

AbstractPolymerization of methyl methacrylate was carried out in aqueous and nonaqueous media in the presence of some sulfonated and carboxylic organic compounds, hydroxyl radicals generated from hydrogen peroxide being used as initiators of polymerization. The occurrence of radical transfer reactions by way of hydrogen atom abstraction from the organic substrates by the ȮH radicals was demonstrated by the detection of sulfonate and carboxyl endgroups in the respective polymers. It was found that the radical transfer reactions were more favored in aqueous media than in nonaqueous systems.
Stereospecific polymerization of α‐methylstyrene by friedel‐crafts catalysts
Authors: Oh Sumi Y. , Higashimura T. , Okamura S. 
Published: April 2003

AbstractThe relationship between stereoregularity and polymerization conditions of α‐methylstyrene has been studied by means of NMR spectra. The effects of solvents and various Freidel‐Crafts catalysts have been investigated. The stereoregularity of poly‐α‐methylstyrene increased with increased polymer solubility in the solvent used and with decreasing polymerization temperature. This behavior is completely different from the stereospecific polymerization of vinyl ethers and methyl methacrylate in homogeneous systems. This may be due to the strong steric repulsion exerted by the two substituents in the α‐position of α‐methylstyrene. For example, with BF3 · O(C2H5)2 as catalyst at −78°C., atactic polymer is obtained in n‐hexane, a nonsolvent for α‐methylstyrene, whereas highly stereoregular polymer is produced in toluene or methylene chloride, good solvents for the polymer. However, the polarity of the solvent and the nature of the catalyst hardly affect the stereoregularity of the polymer.
Nuclear magnetic resonance and x‐ray determination of the structure of poly(vinylidene fluoride)
Authors: Lando J. B. , Olf H. G. , Peterlin A. 
Published: April 2003

AbstractIn this study, wide‐line NMR and x‐ray diffraction have been used in conjunction to study the crystal structure of poly(vinylidene fluoride). Drawn poly(vinylidene fluoride) film was found to contain two crystal phases, the relative amounts of each depending on the draw temperature. Drawing at 50°C. yields a single phase, designated as phase I, while drawing at temperatures between 120 and 160°C. yields a mixture of phase I and a second phase (phase II). The fraction of phase II increases with increasing draw temperature, but this phase was never obtained without some phase I. A tentative orthorhombic unit cell is proposed for phase II. The structure of phase I has been determined from x‐ray data. The unit cell is orthorhombic, space group Cm2m, having lattice constants a = 8.47, b = 4.90, and c (chain axis) = 2.56 A. There are two polymer chains in this unit cell. The conformation of the polymer chains is planar zigzag. The details of this structure have been confirmed by experimentally determining at −196°C. the change in the NMR second moment with the angle between the magnetic field and the draw direction of phase I (drawn at 50°C.), and by comparing these results with a theoretical calculation of the second moments, based on the atomic positions obtained from the proposed structure.
X‐ray and NMR measurements on irradiated polytetrafluoroethylene and polychlorotrifluoroethylene
Authors: Peffley W. M. , Honnold V. R. , Binder D. 
Published: April 2003

AbstractThe effects of 60Co γ‐radiation on polytetrafluoroethylene (PTFE) and polychlorotri‐fluoroethylene (PCTFE) have been studied for radiation doses up to 940 Mrad. The dependence of per cent crystallinity upon irradiation level has been determined from x‐ray analysis. An initial increase in crystallinity in PTFE, attributable to chain scission in the amorphous phase of the material, was found, followed (above 300 Mrad) by a gradual decrease associated with a disordering of the crystallites. No initial increase was observed for annealed samples of PCTFE due to the large initial value of the per cent crystallinity. Above 200 Mrad the crystallinity was found to decrease with accumulated dose. Nuclear magnetic resonance measurements on PTFE have indicated a radiation‐induced broadening of the amorphous component of the NMR line appearing to maximize above 700 Mrad. Similar measurements of PCTFE have shown a narrowing of the crystalline component of the NMR line and subsequent appearance of the amorphous component at approximately 200 Mrad. The data indicate that the radiation‐induced behavior of PTFE and PCTFE is similar above 200 Mrad.
Polymerization of methyl acrylate in aqueous media
Authors: Morris Carolyn E. M. , Alexander A. E. , Parts A. G. 
Published: April 2003

AbstractThe polymerization of methyl acrylate in water and in dilute, aqueous, soap solutions, initiated by potassium peroxydisulfate, has been investigated, a dilatometric method being used to follow the conversion. It has been shown that small amounts of an anionic soap increase the rate of reaction while a cationic soap has the reverse effect. The change of molecular weight with conversion has also been examined as well as the effect of the exclusion of oxygen from the system.
Non‐newtonian behavior of polymers with log‐normal molecular weight distribution
Authors: Conti W. , Gigli I. 
Published: April 2003

AbstractBy choosing suitable approximations to Bueche's function, it is possible to calculate the viscosity versus shear stress for log‐normal molecularly distributed linear polymers. For bulk polymers the mixing rules M̄w, M̄w, M̄z are considered. For values of η/η0 > 0.1 and heterogeneities with M̄w/M̄n > 1.5 the result obtained with any mixing rule is η/η0 = erfc [(1/delta;) log (M0Qh/aK)], where a = π2/6pRT and where the δ and K values are dependent on the heterogeneity ratio Q = M̄w/M̄n and on the type of mixing rule; on the other hand, the h value is independent of the heterogeneity, but depends on the mixing rule. Most experimental data should fit the M̄w mixing rule as one would expect from the zero shear stress mixing rule. Experimental data are compared with the theoretical results.
Oleophilic ion‐exchange resins. IV. Swelling of quaternary ammonium polymers in mixed solvents
Authors: Shida Mitsuzo , Gregor Harry P. 
Published: April 2003

AbstractThe swelling characteristics of an oleophilic anion‐exchange resin in methanol–benzene and ethanol–chloroform mixed solvent systems were compared with those of a conventional anion‐exchange resin. The oleophilic resin was prepared by amination of chloromethylated polystyrene 1% DVB with N,N‐dimethyldodecylamine. It showed a large shift of the swelling peak from polar to less polar solution compositions in both methanol–benzene and ethanol–chloroform systems as compared with the swelling of conventional resins. Total solvent uptake and solvent distribution between resin and solvent phases were also determined. The less polar solvent (benzene or chloroform) was sorbed preferentially by the oleophilic resin over a wide range of composition, while preference for the more polar solvent (methanol or ethanol) by the conventional resin was shown over the entire composition of the mixed solvent systems. The Newman‐Krigbaum treatment of mixed solvents was applied to swelling data on the ethanol–chloroform–oleophilic resin system, where the volume of the gel network plus the solvent imbibed was relatively constant over the entire range of composition. The result suggests a strong similarity of the liquid–liquid interaction terms in this gel phase compared with those in the pure binary liquid phase.
Polymerizations of some diene monomers. Preparations and polymerizations of vinyl methacrylate, allyl methacrylate, N‐allylacrylamide, and N‐allylmethacrylamide
Authors: Kawai Wasaburo 
Published: April 2003

AbstractVinyl methacrylate, allyl methacrylate, N‐allylacrylamide, and N‐allylmethacrylamide were prepared, and these monomers were polymerized in toluene by α,α‐azobisisobutyronitrile catalyst. Cyclization content of poly(vinyl methacrylate) was estimated by infrared spectroscopy to be 50–60% at low conversions, but at the high conversions, due to gelation the polymers were insoluble in the usual organic solvents. Allyl methacrylate did not produce any soluble polymer, even at a low conversion, in contrast with poly‐(vinyl methacrylate). Poly‐N‐allylacrylamide and poly‐N‐allylmethacrylamide were also insoluble in common solvents. It was assumed that the polymers from monomers containing the allyl group might form crosslinks as a result of allyl resonance stabilization.
Photodegradation of poly(methyl methacrylate)
Authors: Allison J. P. 
Published: April 2003

AbstractThe vacuum photodegradation at 30°C. of poly(methyl methacrylate) and copolymers with acrylaldehyde, methacrylaldehyde, and methyl acrylate has been studied. The polymers were examined in the form of expanded films as produced by a freeze‐drying technique. At least one molecule of carbon monoxide is evolved for each chain scission. It is concluded that chain scission in poly(methyl methacrylate) is primarily the result of photoinduced aldehyde groups.
Investigation of autoacceleration effects during the solution polymerization of styrene
Authors: Glass J. E. , Zutty N. L. 
Published: April 2003

AbstractThe possibility of obtaining increases in the rate and degree of polymerization through a decrease in the termination rate in nonviscous, homogeneous solution polymerizations of styrene has been investigated. Decreases in the termination rate were achieved through decreasing segmental diffusion of the propagating macroradical by greater occlusion, on the average, of the radical in the coiled polymeric chain. Coiling of the polymeric chain was effected by polymerizing styrene in thermodynamically poor (θ) solvents near the θ temperature for polystyrene. Examples of such systems are diethyl oxalate at 51.5°C. and cyclohexane at 34.6°C. Polymerization under these conditions did lead to a decrease in the kt/kp2 kinetic ratio; this decrease resulted in increases in the degree of polymerization, but changes in the rate of polymerization, in contrast to the marked increases noted in viscous solution or heterogeneous polymerizations, were not observed. Possible explanations for the latter observations are discussed.
Polyamides from α,ω‐oxaalkanedioic acids having long methylene chain units
Authors: Saotome Kazuo , Sato Kenichiro 
Published: April 2003

AbstractThree series of polyamides were prepared from diamines (hexamethylenediamine, bis‐5‐aminoamyl ether, p‐xylylenediamine) and α,ω‐oxaalkanedioic acids of formula HOOC(CH2)mO(CH2)nCOOH, where m = n = 3–10, in symmetric structures, but m = 3 or 4 in unsymmetric structures. The melting points of these polymers were plotted against the number of carbon atoms of the oxaalkylene groups. The melting points of polymers from each diamine fell on three different curves according to the structures of the dicarboxylic acids: symmetric (CH2)nO(CH2)n; unsymmetric (CH2)3O(CH2)n, and unsymmetric (CH2)4O(CH2)n. A minimum melting point is observed at about the same point of the acid structure in every curve of the unsymmetric dicarboxylic acids. The marked depression in the polymer melting points around the minimum point is attributed to the increase of the entropy of fusion.
Preparation of poly‐p‐xylylenes by electrolysis
Authors: Gilch H. G. 
Published: April 2003

AbstractPoly‐p‐xylylenes were prepared by electrolytic reduction of α,α′‐dihalo‐p‐xylenes at controlled cathode potentials (c.p.). Polymers and halides are formed at the cathode; at the anode the halide is oxidized to halogen. Poly‐p‐xylylene was prepared from α,α′‐dichloro‐p‐xylene (c.p. −1.2 v.) and α,α′‐dibromo‐p‐xylene (c.p. −1.2 v.); poly‐p‐2‐chloroxylylene from α,α′,2‐trichloro‐p‐xylene (c.p. −1.4 v.) and α,α′‐dibromo‐2‐chloro‐p‐xylene (c.p. −1.2 v.); poly‐α,α,α′,α′‐tetrachloro‐p‐xylylene from α,α,α,α′,α′,α′‐hexachloro‐p‐xylene (c.p. −0.7 v.), and poly‐α,α,α′,α′‐tetrafluoro‐p‐xylylene from α,α′‐dibromo‐α,α,α′,α′‐tetrafluoro‐p‐xylene (c.p. −1.1 v.). The cathode potentials were measured and controlled with respect to a saturated calomel electrode. Current efficiencies up to 96% were observed. α,α,α′,α′‐Tetrachloro‐p‐xylylene was identified as an intermediate in the reduction of α,α,α,α′,α′,α′‐hexachloro‐p‐xylene. A general mechanism for these reactions is suggested and discussed. It involves elimination of halide by a two‐electron charge transfer with formation of a xylyl anion, followed by an elimination of halide in α′‐position yielding xylylenes which then polymerize.
Spectroscopic studies of poly(vinyl chloride) and its deuterated derivatives
Authors: Enomoto S. , Asahina M. , Satoh S. 
Published: April 2003

AbstractPoly(vinyl chloride) (PVC) and all its deuterated derivatives were prepared by variation of the polymerization method and polymerization temperature to study the structure of PVC and the mechanism of addition polymerization by infrared spectroscopy and high resolution NMR spectroscopy. The CH and CH2 stretching modes of PVC were assigned completely from the infrared spectra of PVC‐αd1, PVC‐β,βd2 and PVC‐d3. The frequencies of the CCI stretching modes of the polymers depended not only on the substituents in the trans position to the Cl atom across both adjacent CC bonds, but also on the atom attached to the C atom of the CCl bond. The frequency shifts were used to assign the CCl stretching modes of PVC‐βd1 and PVC‐α,βd2 and to study the opening of the double bond of VC in the addition polymerization. The differences of the chemical shifts of the α and β protons of PVC due to the tacticity were determined experimentally by PVC‐β,βd2 and PVC‐αd1 without using the spin‐decoupling technique. With PVC‐α,βd2, the conception of the tetrad was required to interpret the four observed peaks whose intensities changed with the polymerization temperature and the trans–cis composition of the monomer used.
Synthesis and characterization of branched polystyrene. Part II. Fractionation
Authors: Gosnell A. B. , Gervasi J. A. , Schindler A. 
Published: April 2003

AbstractFractionations have been carried out by a column‐elution method on mixtures of linear and branched polystyrene. These had been prepared by anionic polymerization followed by a coupling reaction to form star‐shaped branched polymers. Therefore, the components of the mixture were each of narrow distribution, and their molecular weights differed from each other as multiples of the original single chain length. For single chains in the 25,000–30,000 molecular weight range, separations were accomplished in which the multiples (number of branches) were 1, 2, 4, and 6. By this means, virtually monodisperse samples of the branched polymers could be isolated.
NMR spectra of model compounds of poly(vinyl chloride)
Authors: Abe Yasuaki , Tasumi Mitsuo , Shimanouchi Takehiko , Satoh Shiroh , Chûjô Riichiro 
Published: April 2003

AbstractThe NMR spectra of three stereoisomers of 2,4,6‐trichloroheptane as model compounds of poly(vinyl chloride) have been studied. Spectra were observed at 60 and 100 Mc./sec., both at room temperature and at high temperatures. A spin‐decoupling experiment was performed. Computational analysis of the spectra was carried out on an IBM 7090 computer. The difference of the chemical shifts of the two meso methylene protons at 60 Mc./sec. was found to be ca. 7 cps. for the isotactic three‐unit model while it was ca. 16 cps. for the isotactic two‐unit model or heterotactic three‐unit model. The spectra of poly(vinyl chloride) were interpreted reasonably on the basis of this result. Observed values of vicinal coupling constants of model compounds were interpreted as the weighted means of those for several conformations, and the stable conformations of the models were determined.
Polymerization of aromatic nuclei. X. Polymerization of benzene to p‐polyphenyl oligomers by nitrogen dioxide—aluminum chloride
Authors: Kovacic Peter , Hopper Roger J. 
Published: April 2003

AbstractBenzene was polymerized to p‐polyphenyl oligomers by nitrogen dioxide–aluminum chloride. Polymer production was favored by AlCl3:NO2 ratios of at least 2, long reaction times, and higher temperatures. Evidence for the polymer structure was obtained from elemental analyses, oxidative degradation, solubility, molecular weight, functional group tests, low molecular weight products, and infrared and ultraviolet spectra. The chains contained small amounts of chloro, amino, hydroxyl, and carboxyl substituents. Molecular weight data on the benzene‐soluble portion (40–71%) revealed an average of 4–6 phenylene units per chain. Under altered conditions nitrobenzene could be obtained as the major product, indicating the sensitivity of the system to changes in reaction variables. With nitrobenzene as oxidant, a similar type of polymer resulted. The theoretical aspects are discussed.