bluuebunny/crossref_metadata_2025_split huggingface dataset:
Proton magnetic resonance study on the structures of phenol–formaldehyde resins
Authors: Woodbrey James C. , Higginbottom Harold P. , Culbertson Harry M. 
Published: April 2003

AbstractBecause of their commercial importance, the reaction sequences and structures of resins produced when phenol reacts with formaldehyde have been studied by numerous different chemical and physical methods. Many details concerning these reactions and complex chemical structures are still not entirely understood. Most of the experimental methods used have yielded only qualitative information. Many of these methods have been applicable only to the lower molecular weight portions of soluble prepolymers. The present work describes proton magnetic resonance (PMR) methods which yield detailed and quantitative number‐average structures for any soluble phenol‐formaldehyde resin. It is shown that benzyl‐type hemiformals make substantial contributions to the structures of many resoles and that these functionalities exhibit relatively high stability under certain conditions of initial cure. The structures of several resins are discussed in terms of certain aspects of reactions which occurred during the resin syntheses. These reactions include hydroxymethylations and condensations yielding diphenylmethane‐type and dibenzyl ether‐type bridges. To define the mechanisms and rates of the various reactions at different temperatures and under different catalytic conditions, a much more detailed study is required. Potentially, the PMR methods described can provide most of the necessary quantitative data.
Dye‐sensitized photopolymerization. I. Polymerization of acrylamide in aqueous solution sensitized by methylene blue–triethanolamine system
Authors: Chen Catherine S. Hsia 
Published: April 2003

AbstractThe polymerization of aqueous acrylamide induced by visible light in the presence of methylene blue–triethanolamine as the sensitizing system has been investigated. The polymerization was found to follow a nonsteady‐state kinetic scheme. The rate was proportional to the first power of the absorbed light intensity and approximately proportional to the initial monomer concentration. The rate passed through a maximum as a function of the initial dye concentration. The molecular weights of the polymers were in the range of one million. The molecular weights were independent of the absorbed light intensity, essentially directly proportional to the initial monomer concentration, and decreased logarithmically with the initial dye concentration. Both spectroscopy and polymerization behavior suggest that the monomeric form of the dye is a photosensitizer while the associated form is a chain terminator. The kinetic chains were terminated unimolecularly, and the molecular weights were governed by a chain transfer process.
Dilute solution properties of nylon 66 dissolved in 2,2,3,3‐tetrafluoropropanol
Authors: Saundres P. R. 
Published: April 2003

AbstractLight‐scattering and viscosity measurements have been made on dilute solutions of nylon 66 dissolved in 2,2,3,3‐tetrafluoropropanol. The polyelectrolyte behavior of polyamides in carefully distilled solvent is due to traces of water in the solvent. If care is taken to exclude water, 2,2,3,3‐tetrafluoropropanol is a nonionic solvent for nylon 66. The polyelectrolyte effects of nylon 66 in the wet solvent can be repressed by the addition of sodium trifluoroacetate. The action of the sodium trifluoroacetate is to immobilize the water molecules in solution rather than to act as an electrostatic screen. Molecular weights estimated from the light‐scattering data and the relation between intrinsic viscosity and second virial coefficient are identical with the results based on measurements in the solvent system formic acid–water–sodium formate.
Crystalline state of cellulose in fresh and dried mature cotton fiber from unopened bolls as studied by x‐ray diffraction
Authors: Heyn A. N. J. 
Published: April 2003

AbstractThe crystallinity of cellulose in the undried cotton fiber, fresh from the unopened but mature boll, was studied by x‐ray diffractometer methods and compared with the crystallinity of portions of fibers from the same samples either dried directly or from which the water has been removed in various “indirect” ways calculated to better preserve the original structure including: (a) Solvent exchange, (b) freeze‐drying, (c) drying above the critical temperature of liquids and (d) drying after the cellulose of the wet fiber has been crosslinked. The difference in crystallinity observed between directly and indirectly dried fibers indicates that a crystallization process must take place during the direct drying of the water‐wet fiber. This crystallization process is promoted by the presence of water and inhibited or prevented when the fiber is dried indirectly. An increase of the degree of crystallinity due to wetting can be explained by assuming that the crystallization, which had been suppressed in the indirectly dried fiber takes place subsequently upon drying of the rewetted fiber. That the indirect methods preserve entirely or partially, such amorphous structure as is originally present is confirmed by the lower density and higher dyestuff accessibility of such fibers.
Heterogeneous polymer systems. I. Polymeric oil‐in‐oil emulsions
Authors: Molau Gunther E. 
Published: April 2003

AbstractA novel class of emulsions has been introduced. Emulsions of this class comprise two immiscible polymer solutions and a graft copolymer as an emulsifying agent. The name polymeric oil‐in‐oil emulsions (POO emulsions) has been suggested for the new emulsions. The concept has been verified with several systems of polymer solutions. The polymers used here are poly(ethyl acrylate), poly(methyl methacrylate), polystyrene, polyvinyltoluene, poly‐p‐tert‐butylstyrene, and a styrene/acrylonitrile copolymer.
Branching in poly(butadiene‐co‐styrene). IV. Retardation of radiation‐induced branching
Authors: Blachford J. , Robertson R. F. 
Published: April 2003

AbstractThe composition and yield of the evolved gas and the resulting changes in infrared and ultraviolet spectra have been examined for the irradiation of poly(butadiene‐co‐styrene). Apart from crosslinking, the major changes which occurred during the reaction were the evolution of hydrogen and the destruction of vinyl groups. For every 100 e.v. of radiation energy absorbed 0.45 molecules of hydrogen were evolved, G(H2) = 0.45, and 6.1 vinyl groups were destroyed, G(‐vinyl) = 6.1. These results have been compared with the yield of crosslinks, Gx = 1.60. Addition of N‐phenyl‐β‐naphthyl‐amine to the polymer reduced the gas yield to a greater extent than predicted by the “mixture law” (which states that the yield of a product from component X is directly proportional to the electron fraction of X). Over the additive concentration range of 2–11%, the gas yield was constant. This behavior is identical to that found previously for the crosslink yield. An explanation of these results has been given which involves the occurrence of processes which exhibit a negative deviation from the mixture law together with processes which exhibit a positive deviation. The destruction of the additive during the irradiation of a sample containing initially 0.52% additive has been determined. The results indicate that the additive protects the polymer mainly by charge transfer or excitation energy transfer.
Viscosity behavior of branched and linear potassium carboxymethyl dextrans
Authors: Pasika W. M. , Cragg L. H. 
Published: April 2003

AbstractSamples of branched and linear dextran of near identical intrinsic viscosities have been carboxymethylated to varying degrees and converted to the potassium salts. The reduced viscosity–concentration curves of the branched and linear carboxymethyl dextran polyelectrolytes of identical degree of substitution in aqueous potassium chloride solutions (0.001N and 0.0005N) were compared. Significant differences were observed to exist. At low degrees of substitution (0.06–0.20 carboxymethyl group per anhydroglucose unit) the branched macroion possessed larger reduced viscosities than did its linear counterpart. At a higher degree of substitution (ca. 1.0 carboxymethyl group per anhydroglucose unit) the reduced viscosity curves of the branched and linear macroions crossed. These differences were shown to be independent of shear rate, molecular weight and molecular weight distribution. It is concluded that branching is responsible for the differences in the reduced viscosity–concentration behavior of the branched and linear potassium carboxymethyl dextran samples because of the higher charge density in the branched macroion.
Investigation of thiazole polymers for heat‐resistant fibers and films
Authors: Sheehan W. C. , Cole T. B. , Picklesimer L. G. 
Published: April 2003

AbstractSeventeen thiazole polymers were prepared by the polycondensation of bis‐α‐bromoketones with dithioamides, and the polymers were investigated for preparing heat‐resistant fibers and films. Tough fibers and films were made from four of the polymers; however, these polymers had low melting points (164–250°C.). All of the other polymers studied except these did not melt below 500°C., and they had excellent thermal stabilities, but they did not have good fiber‐ and film‐forming properties because of their low molecular weights. All of the polymers prepared had some crystallinity. Two of the polymers were soluble in organic solvents; the other were soluble only in strong acids. Model compounds of four of the polymers were prepared, and the properties and structures of the compounds were compared with those of the polymers.
Study of swelling in two new ion exchange membranes
Authors: Hodgdon Russell B. , Boyack James R. 
Published: April 2003

AbstractThe synthesis of two new ion‐exchange membranes is presented. These are a partially sulfonated polystyrenesulfonic acid resin and an interpolymer system composed of sulfonated polystyrene–divinylbenzene polymerized within a poly(vinylidene fluoride) matrix. Each of these systems allows control of ion exchange capacity and physical properties over a wide range. The second is especially useful, in that ion‐exchange capacity and swelling characteristics may be controlled independently. It also has the distinct advantage of giving a clear, flexible film even with high crosslinking. On the basis of certain simplifying assumptions an equation is derived which permits approximate calculation from equilibrium water uptake data of an elastic constant which measures the resistance of the membrane to swelling forces. Equilibrium water content data for the two membrane systems are treated with this equation and analyzed in terms of internal structure.
Ferrocene‐containing polymers. V. Polycondensation of N,N‐dimethylaminomethylferrocene
Authors: Neuse Eberhard W. , Quo Edward 
Published: April 2003

AbstractThe self‐condensation of the ferrocenyl Mannich base, N,N‐dimethylaminomethylferrocene, in the presence of a ZnCl2HCl catalyst system in the melt phase leads to soluble polymers containing ferrocenylene units interlinked by methylene groups. The crude condensation products exhibit number‐average molecular weights in the range 4000–8000. Elemental and infrared spectroscopic analyses as well as viscometric data show the structure to be essentially identical with that of the polymer derived from hydroxymethylferrocene described in an earlier communication. The optimum molar ratio of the reactants (Mannich base, ZnCl2, and HCl) is 2:1:2. Dimethylammonium tetrachlorozincate has been isolated as by‐product, and an intermediary complex composed of Mannich base, ZnCl2, and HCl in the same 2:1:2 ratio has been intercepted during the polycondensation. Some mechanistic inferences are discussed.
Poly‐α‐cyanostyrene
Authors: Hughes L. J. , Perry Eli 
Published: April 2003

AbstractThe monomer α‐cyanostyrene polymerized at a very slow rate under the influence of free‐radical initiators. Rapid polymerization to high molecular weight material was achieved by using anionic initiators (tri‐n‐butylphosphine and tetrakisdimethylaminotitanium). The polymer made at −78°C. was colorless, fusible, soluble, and had a number‐average molecular weight of over 5,000. The polymer prepared at 0°C. was brown, insoluble, and infusible. None of the polymer showed order in the x‐ray diagram. The rate of dimerization of α‐cyanostyrene under a wide variety of conditions was measured. Two new derivatives of the intermediate, 3‐(N,N‐dimethylamino)‐2‐phenylpropionitrile were prepared: the methiodide, m.p. 242–245°C. (decomp.), and the picrate, m.p. 116.5–117.5°C.
Preparation and aromatization of poly‐1,3‐cyclohexadiene and subsequent crosslinking. III
Authors: Cassidy P. E. , Marvel C. S. , Ray Suvas 
Published: April 2003

AbstractThe polymerization of 1,3‐cyclohexadiene with n‐butyllithium has given white polymers with inherent viscosities up to 0.23 and conversions to 98%. Bromination and pyrolysis of these polymers lead to polyphenyls which can be successfully sulfonated. then fused in molten alkali to give phenols, and finally crosslinked with formaldehyde. The final products display good heat stability, in that there is no weight loss on heating to 400°C. and only 30% loss at 900°C.
Reactivity of condensed‐ring hydrocarbons as polymerization retarders
Authors: Ihrig Judson L. , Sood Satya Pal 
Published: April 2003

AbstractSeventeen condensed‐ring hydrocarbons have been investigated as retarders or inhibitors of styrene and methyl methacrylate polymerization. Rates were measured dilatometrically. Nine of the compounds tested retarded or inhibited the polymerization of styrene, but methyl methacrylate appears not to be affected by this class of substances. Styrene data obtained are examined in the light of Fukui's “frontier electron” formalism for correlating structure and reactivity. It is concluded that the principal locus of radical attack is at the meso carbon atoms, Fukui's (Ss) region, and that a substantial value of the (Ss) density index is required for retardation, although when the molecule also possesses an appreciable (Sp) index, a synergistic action is noted. The point is made that since condensed‐ring hydrocarbons do not have “functional groups” in the sense that quinones and other retarders do, the effect of monomer reactivity is likely to be of added importance in determining retarder efficiency. The lack of retardation effects in polymerizing methyl methacrylate is interpreted from this standpoint. A reverse chaintransfer reaction is tentatively proposed to account for the observed behavior.
Mechanism of the anionic polymerization of methyl methacrylate. IV. Calculated molecular weight distributions resulting from a reversible termination by a bimolecular exchange reaction
Authors: Krause Sonja , Defonso Lester , Glusker Donald L. 
Published: April 2003

AbstractThe previous papers in this series contain the experimental results which demonstrated the complexity of the homogeneous, nonterminated, anionic polymerization of methyl methacrylate. In order to explain the observed broad molecular weight distributions, it was necessary to postulate reversible “pseudo‐termination” reactions, by which a large fraction of the total anions present in the system became inactive toward further polymerization, yet had a finite probability of recovery of polymerization activity by some process, such as ligand exchange, ring opening of a cyclic complex, etc. In this paper, we have examined the quantitative consequences of a mechanism in which this pseudotermination reaction occurs by a bimolecular exchange of activity between one active and one inactive chain. It has been possible to calculate Mw/Mn, the ratio of weight‐average to number‐average molecular weights, as a function of the fractional conversion α, the initial monomer to initiator ratio, M0/I0, the fraction of total initiator as active chains, C1/I0, and the ratio of rate of exchange of activity to rate of propagation, kt/kp. The major results of these calculations are: (1) any value of Mw/Mn between 1 and infinity is possible at α = 1; (2) Mw/Mn at α = 1 decreases as kt/kp increases; (3) Mw/Mn at α = 1 increases as M0/I0 increases when kt/kp and C1/I0 are small—under some conditions Mw/Mn at α = 1 increases and then decreases slightly as M0/I0 increases; (4) Mw/Mn goes through a maximum during polymerization if kt ≠ 0; (5) Mw/Mn at any α decreases as C1/I0 increases, for constant M0/I0 and kt/kp. Concentrations of individual chains of any given length as a function of time may be readily calculated for the two special cases kt/kp → 0 or ∞.
A study on a three‐component polymer formation
Authors: Ravve A. , Khamis J. T. , Mallavarapu L. X. 
Published: April 2003

AbstractSolution terpolymerization studies, with addition of a mixture of monomers and initiator at a constant rate to the solvent, are reported. The monomers represented are styrene, 2‐ethylhexyl acrylate, and glycidyl acrylate, with polymerization initiated either by di‐tert‐butyl peroxide or dicumyl peroxide. Data are presented regarding polymer composition with respect to the three monomers, rates of conversion to polymer, and effect of changes in monomer and initiator composition. Also included are results of polymer fractionation studies utilizing molecular weight determination of the fractions by high‐speed membrane osmometry. The steady‐state equation, which is commonly used in the kinetic treatment of solution or bulk polymerizations carried to low conversions, was applied to this continuous feed system even up to high conversions. Furthermore, with the proper choice of initiator, narrower molecular weight distributions were obtained.
Entropy and heat of fusion of polymers
Authors: Kirshenbaum I. 
Published: April 2003

AbstractMethods are presented for estimating the entropy and heat of fusion of polyolefins, polyamides, polyesters, etc. Although the formulas are approximate, good agreement is obtained with experimental values, where available. For example, the calculated entropies for polypropylene, polyoxymethylene, nylon 66, polyester 210, and poly(ethylene terephthalate) are 5.4, 3.4, 11.2, 8.3, and 5.9 e.u./mole of repeating unit, respectively, as compared to the experimental values of 5.4, 3.5(3.9), 11, 7, and 5.8(5.4), respectively. Application of the formulas to the polyamides support the calorimetric and DTA estimates of the heats of fusion which are significantly greater (by 25–75%) than those determined by the diluent method. Thus, the calculations also indicate that the heats of fusion of the polyamides are higher than those of similar polyesters.
Sugar polythioacetals
Authors: Horvath Elizabeth G. , Gardlund Sharon , Sen Subodh K. , Berry James W. , Deutschman Archie J. 
Published: April 2003

AbstractSugar polythioacetals have been prepared by polymerization of sugars with dithiols in dioxane solution with hydrogen fluoride catalyst. Polymerization was also carried out by using liquid hydrogen fluoride as solvent and catalyst. The polymers are colorless powders with inherent viscosities in the range of 0.03–0.24 and melting points of 81–160°C. The polythioacetals of the shorter‐chain dithiols are soluble in polar solvents; those of the longer‐chain dithiols are partially soluble.
Thermochemiluminescence of polycarbonate and polypropylene
Authors: Barker R. E. , Daane J. H. , Rentzepis P. M. 
Published: April 2003

AbstractExperimental techniques for observing total and spectral thermochemiluminescence (TCL) are discussed in general along with some data for the systems polycarbonate–O2, polycarbonate–CO, and polypropylene–O2. Since TCL is the process whereby heated materials undergo thermally activated reactions and emit light in excess of the amount prescribed by the blackbody radiation law, its study may be expected to yield information about the structure and degradation of the materials. It has been observed that TCL spectra are both time‐ and temperature‐dependent. A simple mathematical model for analyzing TCL data under conditions of a linear heating rate is discussed. The result also should be of use in thermogravimetric analysis.
Ethylene–propylene copolymers. I. Monomer reactivity ratios
Authors: Bushick R. D. 
Published: April 2003

AbstractThe copolymerization of ethylene and propylene with diisobutylaluminum chloride and various vanadium‐containing compounds gave a series of reactivity ratio values for ethylene which decreased in the order: VO(O‐n‐Bu)3 > VOCl(OEt)2 > VOCl2OEt > VO(OEt)3 ≃ VOCl3. All of the catalyst systems were extremely sensitive to changes in the ethylene feed concentration. The reactivity ratio product suggested a random arrangement of monomer units with each catalyst system except VOCl3.
Synthesis of vinylphosphonium compounds
Authors: Rabinowitz Robert , Henry Arthur C. , Marcus Ruth 
Published: April 2003

AbstractTributylvinylphosphonium bromide has been prepared by sodium carbonate dehydrobromination of the 2‐bromoethyl salt resultant from the reaction of tributylphosphine and dibromoethane. Tributylvinylphosphonium chloride was prepared from the bromide by ion exchange. Triethylvinylphosphonium bromide, tricyclohexylvinylphosphonium bromide, and dimethylphenylvinylphosphonium bromide were prepared by sodium carbonate treatment of the acetate resulting from acetic anhydride acetylation of the salt formed from the reaction of ethylenebromohydrin and the corresponding phosphine. An attempt to prepare a vinylphosphonium salt directly by heating vinyl bromide and tributylphosphine at 160°C. in an autoclave gave no isolable product; however, infrared evidence indicated the possible presence of the expected vinylphosphonium salt.
Structural study of phenol–formaldehyde polymers with proton magnetic resonance
Authors: Hirst Robert C. , Grant David M. , Hoff Raymond E. , Burke William J. 
Published: April 2003

AbstractProton magnetic resonance spectra were obtained for a number of representative phenol–formaldehyde dimers and trimers of known structure and for related compounds having methyl or chloro substituents on the aromatic ring. The data thus obtained, particularly for the methylene protons, were used in the interpretation of the structure of well characterized, linear phenol–formaldehyde polymers and the corresponding halogenated polymers prepared by the condensation of o‐ and p‐chlorophenol with formaldehyde. In all cases there was a shift to lower field as the methylene linkage was varied from para‐para to ortho‐para to ortho‐ortho, although in certain instances the ortho‐para and ortho‐ortho peaks moved very close together. The spectra obtained indicated that the condensation of o‐chlorophenol with formaldehyde proceeds in an essentially random manner, since the ratio of ortho‐ortho to ortho‐para to para‐para methylene linkages was found to be 1:2:1, within the limits of experimental error. The preliminary results obtained in this work clearly demonstrate the potential utility of PMR as a valuable tool in the characterization of the highly complex products obtained from phenol–formaldehyde systems.
Copolymer composition and microstructure
Authors: Ito Koichi , Yamashita Yuya 
Published: April 2003

AbstractA simple theory and treatment to characterize copolymer composition and microstructure was developed by applying the statistical stationary process given by Coleman and Fox to the three models in binary copolymerization in which the last one, two, and three monomer units in the growing polymer chain affect the probability of monomer addition. A simple method to distinguish the three models from each other is also presented. The theory was applied to a cationically obtained β‐propiolactone–3,3‐bischloromethyloxetane copolymer reported by Tada et al., to indicate how the penultimate units affect the copolymer composition and microstructure. The significance of the monomer reactivity ratios from the standpoint of copolymer microstructure is discussed briefly.