bluuebunny/crossref_metadata_2025_split huggingface dataset:
Applicability of polymer network theories to gels obtained by crosslinking a polymer in solution
Authors: Mukherji B. , Prins W. 
Published: April 2003

AbstractCurrent polymer network theories exhibit inconsistencies which show up particularly clearly when one considers the three‐dimensional deformation (swelling) of networks which are prepared by crosslinking a polymer in solution. A check on the theories can only be obtained if one knows precisely the number of crosslinks in the network and if a range of deformations (range of swelling ratios) is imposed on the network. To this end a series of seven gels was prepared by crosslinking secondary cellulose acetate (D.S. = 2.42) in dioxane solution (5–10%) with dianisidine diisocyanate. The number of chemical crosslinks was determined by reacting unused isocyanate groups with C14‐labeled methanol. Subsequently, changes in the degree of swelling of the gel, induced by increasing concentrations of cellulose acetate in dioxane and methyl acetate solutions around the gel, were followed by measuring accurately the changes in length of 2‐cm. strips under a travelling microscope. At equilibrium swelling the activities of the solvent inside and outside the gel are equal. For the outside solutions the activities were derived from osmometry. The inside activities derive from a mixing term and an elastic deformation term. The mixing term was approximated by using the Flory‐Huggins expression with an interaction parameter, as obtained from osmometry on a derivative, which was prepared by reacting cellulose acetate with an excess of diisocyanate, thus avoiding network formation. By means of the various known theoretical expressions for the elastic deformation term, the swelling data allow the calculation of the number of crosslinks in the gels. All theories lead to far fewer crosslinks than are known to be there on the basis of the chemical analysis. This has never been observed to the same extent before, but may be specific for gels obtained by crosslinking in solution. One is forced to conclude that none of the existing theories are applicable. The data can be explained, however, by postulating that the configurations of the chains between crosslinks do not follow a Gaussian distribution, but are instead given by ω(r)dr = ωx(x)‐ωy(y)ωz(z) dxdydz, where ωx(x) = C|x|n exp { −bx2}. Such a non‐Gaussian distribution might arise because of topological restrictions, possibly including those due to the excluded volume. For the free energy of elastic deformation we find, following James and Guth's reasoning but using the new distribution function:

where v is the number of chains in the network and λx, λy, and λz are the deformation ratios with respect to the unstrained state. In the well known Gaussian theories, the term n + 1 is absent and in front of the logarithm instead of n either 0, 2/f, or 1 (f = functionality of the crosslink) is found, depending on whether the result of James and Guth, Flory and Wall, or Hermans is used, respectively.
Epoxidation of poly‐2‐methyl‐6‐allyl‐1,4‐phenylene oxide and copolymer of 2‐methyl‐6‐allyl‐4‐bromophenol and 2,6‐dimethyl‐4‐bromophenol
Authors: Tsou K. C. , Hoyt H. E. , Halpern B. D. 
Published: April 2003

AbstractEpoxidized homopolymer of 2‐methyl‐6‐allyl‐4‐bromophenol and its copolymers with 2,6‐dimethyl‐4‐bromophenol have been prepared. When more than theoretical amount of peracetic acid was used, chain degradation occurred. This chain degradation was also demonstrated by the reduction in viscosity of poly‐(2,6‐dimethyl)‐1,4‐phenylene oxide when treated with peracetic acid under similar conditions.
Endgroup studies in persulfate‐initiated vinyl polymer by dye techniques. Part II. Initiation by redox persulfate systems
Authors: Ghosh Premamoy , Chadha Subhash Chander , Palit Santi R. 
Published: April 2003

AbstractPoly(methyl methacrylate) samples obtained by aqueous redox initiation with persulfate in conjuction with reducing sulfoxy compounds such as HSO3−, SO3−, S2O3−S2O4−, and S2O5− are found by dye techniques to contain both hydrolyzable sulfate endgroups (derived from persulfate) and nonhydrolyzable sulfonate endgroups or the like (derived from the activator) to an average total of about 2 endgroups per polymer molecule. Sulfide (S−) is unique as an activator, as only sulfate endgroups ( no sulfonate or hydroxyl) have been found in the polymers. Persulfate used in conjunction with other activators (such as Ag+, Fe++ hydrazine and hydroxylamine, aliphatic amines, alcohols, reducing acids and their salts, etc.) produce polymers with both sulfate and hydroxyl endgroups. Incorporation of sulfate endgroups is favored under basic conditions and tends to be suppressed under acid conditions.
Polymers containing the cyclopentyl and cyclohexyl groups
Authors: Ketley A. D. , Ehrig R. J. 
Published: April 2003

AbstractPolymers have been prepared from a group of monomers containing the cyclohexyl and cyclopentyl groups. These monomers were of the type (C6H11)(CH2)nCHCH2, (where n = 0–3) and (C5H9)(CH2)nCHCH2 (where n = 0−1). Both Ziegler‐Natta and Friedel‐Crafts catalysts were used. By comparison of the infrared spectra of corresponding polymers prepared with the two types of catalysts, it has been shown, for the cyclohexyl compounds, that intramolecular hydride transfers take place to a significant extent during the propagation step of the Friedel‐Crafts polymerizations. These hydride transfers result in the formation of a tertiary carbonium‐ion end which, on propagation, leads to a polymer in which cyclohexyl groups are part of the main chain. The cyclopentyl compounds, however, do not behave in this way. In this case, the relative reactivities of the tertiary and secondary carbonium ions are such that propagation through the latter is favored. Attempts to polymerize 2,4‐spiroheptane and 2,5‐spirooctane to give model compounds for the “rearranged” polymers are also reported.
Reaction of polystyryllithium with carbon dioxide
Authors: Wyman D. P. , Allen V. R. , Altares T. 
Published: April 2003

AbstractA benzene solution of polystyryllithium of narrow chain length distribution was found to react with carbon dioxide to form (upon acidification) not only the corresponding polystyrene carboxylic acid but also significant amounts of di‐polystyryl ketone and tri‐polystyryl carbinol. The amounts of the latter two products were somewhat dependent on the rate at which carbon dioxide could be added to the system. Thus, the yields of di‐polystyryl ketone and tri‐polystyryl carbinol were 28% and 12% respectively, if termination was accomplished by allowing gaseous carbon dioxide to diffuse into the system, but the total yield of these products was only 22% if the termination was carried out by pouring the polystyryllithium solution onto crushed, solid Dry Ice. Lithium polystyrene carboxylate was found to be partly associated in benzene and cyclohexane, but the free acid was not.
Polymerization of tert‐butyl crotonate
Authors: Miller M. L. , Skogman J. 
Published: April 2003

AbstractLithium alkyls and phenylmagnesium bromide, in toluene, and lithium‐naphthalene, in dimethoxyethane, polymerize tert‐butyl crotonate. Sodium naphthalene produces only low polymer (Mn <3000), and potassium naphthalene gives no polymer. Even lithium naphthalene, which polymerized tert‐butyl crotonate readily, fails to polymerize tert‐butyl tiglate. Free radicals polymerize neither tert‐butyl crotonate nor tert‐butyl tiglate. Poly(tert‐butyl crotonate) formed in the presence of lithium naphthalene is noncrystalline, in the presence of lithium alkyls, either noncrystalline or partly crystalline, and in the presence of phenylmagnesium bromide, highly crystalline. Poly(crotonic acid) was prepared from poly(tert‐butyl crotonate).
A study of the statistical character of anionic polymers
Authors: Nanda V. S. , Jain R. K. 
Published: April 2003

AbstractThe effect of initiation and propagation rate constant ratio on the statistical character of termination‐free anionic polymers is discussed. For obtaining the expressions for the size distribution and the averages, we have followed a mathematical procedure which might prove useful in the treatment of more complicated problems. The conditions under which the ultimate polymer has an appreciable or negligible inhomogeneity are clearly stated.
Polymerization of higher aldehydes. III. Elastomeric polyacetaldehyde
Authors: Vogl O. 
Published: April 2003

AbstractAmorphous elastomeric polyacetaldehyde was prepared in bulk and in solution using cationic initiators. This polymer is the same as Letort's polyacetaldehyde. The acetaldehyde polymerization must be conducted at −40°C. or lower in order to overcome the competitive trimerization or tetramerization. The reactivity of a number of initiators can be modified by using different solvents. The influence of temperature and type of initiator and solvent on the polymerization was studied.
Adsorption of poly(vinyl acetate‐C14) on smooth, geometrically simple surfaces
Authors: Weatherwax R. C. , Tarkow Harold 
Published: April 2003

AbstractPoly(vinyl acetate‐C14)(PVA) was adsorbed from a variety of benzene and carbon tetrachloride solutions on swollen and shrunken cellophane film, on glass, and on cellulose acetate film. The surfaces were geometrically simple, permitting mechanical measurements of the areas. Glass, shrunken cellophane, and cellulose triacetate adsorbed equal amounts of PVA. Swollen cellophane, however, adsorbed 40 times as much PVA as shrunken cellophane. Desorption experiments indicated that the high PVA adsorption on swollen cellophane showed the high reactivity of the surface rather than the diffusion of PVA into the cellophane.
Synthesis and electrical conductivity measurements on semiconducting organic polymers derived from nitriles
Authors: Wildi B. S. , Katon J. E. 
Published: April 2003

AbstractA number of polymeric organic semiconductive materials derived from low molecular weight nitriles are described. These infusible, insoluble materials possess electrical resistivity values which are remarkably low for organic materials. The synthesis and resistivity–temperature behavior of these materials is described and their probable structures discussed.
Thermal degradation of ethylene bis(N‐phenylcarbamate)
Authors: Beachell H. C. , Son C. P. Ngoc 
Published: April 2003

AbstractThe pyrolysis of ethylene bis(N‐phenolcarbamate) was studied as the simplest model of a polyurethane. The degradation occurs by a double process of decomposition involving the simultaneous formation of 3‐phenyl‐2‐oxazolidone, carbon dioxide, and aniline and a partial dissociation into monocarbamate and phenyl isocyanate. Further reaction produces ethylene oxide, N,N′‐diphenylethylenediamine, N,N′‐diphenyl‐2‐imidazolidone, and N,N′‐diphenylurea.
Polybenzimidazoles. I. Reaction mechanism and kinetics
Authors: Wrasidlo Wolfgang , Levine Harold H. 
Published: April 2003

AbstractPoly‐2,2′‐(m‐phenylene)‐5,5′‐bibenzimidazole forms, via two or three intermediates, when 3,3′‐diaminobenzidine and diphenyl isophthalate are condensed. Kinetic data indicate rapid consumption of 3,3′‐diaminobenzidine to form an aldol type intermediate which evolves water to form a Schiff base which in turn evolves phenol to form the final polymer. Phenol evolution is the rate‐determining step. The postulated Schiff base can possess stereoisomerism. Intramolecular hydrogen bonding which can occur in the syn‐isomer offers an explanation why the condensation affords a linear polymer. The combined effects of intramolecular hydrogen bonding and added resonance stabilization in the Schiff base are possible reasons why phenol evolution is the rate‐determining step and why the condensation requires high reaction temperatures.
Mechanism of alternating inter‐intramolecular propagation. II. General kinetics
Authors: Gibbs William E. 
Published: April 2003

AbstractThe general kinetics of alternating inter‐intramolecular propagation are presented and discussed. The major factor which determines the microstructure of the polymer, the relative rates of the intramolecular and intermolecular reactions is examined. From the general kinetics methods are proposed for the determination of the ratio of rate constants for these reactions. A simple method utilizes the equation: [m1]/[M3] = 1 + (kc/k11)(1/[M1]0), where [m1] is the concentration of monomer units in the polymer, [M3] is the concentration of uncyclized units, [M1] is a parameter related to monomer concentration, kc is the rate constant for cyclization and k11 the rate constant for linear propagation. Other methods which may give information on the nature of the termination reaction are discussed.
Study of the hexamethylenediamine–cellulose complex
Authors: Segal Leon , Eggerton F. V. 
Published: April 2003

AbstractComplete conversion of the cellulose crystal lattice to that of the hexamethylene diamine–cellulose complex was attained with diamine solutions of 75% and greater. Solutions of 70% or less produced only partial conversion, although the samples contained high diamine contents. Evaporation temperatures over 90°C. reduced these diamine contents and resulted in partial lattice conversion. Neither this effect nor those following have been observed in the ethylenediamine–cellulose complex. The complex did not change while held in vacuum over sodium hydroxide pellets but gained weight when held in air. After long exposure the yarn was stiff and coated with white powder believed to be hexamethylenediamine carbamate. Attempts to react the complex with cellulose and diamine reactants were not successful. Evidence could not be found for a 2:1 molecular ratio between anhydroglucose units and diamine. Extent of fiber swelling was related to diamine content of the fiber and not to distention of the unit cell. Differences were observed in the intensities of the 101 and 101 x‐ray interferences of the cellulose I and cellulose II complexes.
Glass transitions of polyoxetanes
Authors: Stratta J. J. , Reding F. P. , Faucher J. A. 
Published: April 2003

AbstractGlass transition data of polyexetanes suggest that the responsible segmental chain motions are rather short range in nature. The incorporation of three different structural features within the repeat unit of a polyoxetane results in three separate and independent transition temperatures. The temperature positions of the transitions arising from different structures within the chain are essentially the same as observed in other polymers with a similar structural element. Structural groups and their corresponding transitions which were studied in combination are: CH2CH2CH2 at −125°C., CH2OCH2 at −50 to −70°C., and CH2CHCH3CH2 or OCHCH3CH2 at −20 to −30°C.
Polymers and copolymers of vinyl pinolate and some reactions with isocyanates
Authors: Malzahn R. A. , Griffith J. H. , Marvel C. S. , Hedrick Glen W. , Lewis J. B. , Mobley Carolyn R. , Magne F. C. 
Published: April 2003

AbstractVinyl pinolate has been synthesized, and its homopolymers and copolymers with vinyl chloride and vinyl acetate have been prepared. The reactions of copolymers of vinyl pinolate with vinyl acetate and vinyl chloride with some isocyanates were investigated. The emulsion copolymer of vinyl pinolate and vinyl chloride has been evaluated as a nonrigid plastic.
Processus de l'ecoulement visqueux des hauts polymères
Authors: Bauwens Jean‐Claude 
Published: April 2003

AbstractTwo recent theories concerning the viscosity of high polymers are summarized: the first one, by Bueche, is based on a complex activation process; the other one, established by Cohen and Turnbull to explain the empirical equation of Williams, Landel, and Ferry, is based on the value of the free volume. The discrepancies with the experimental values are emphasized. A mechanism of deformation is proposed which implies that the displacement of a segment of a macromolecule requires the localization of no holes, at least, in a volume which contains No segments Then, the variation of the number of holes with the temperature is computed, with account of the flex energy of the backbone chain and the formation energy of holes (like Flory, and Gibbs and di Marzio). The theoretical results are in good agreement with the experimental values of the variation of the viscosity with the temperature, the second‐order transitions (thermal expansion and heat capacity), and the variation of the glass temperature with the molecular weight. A simple activation process can also produce the deformation and has the most important contribution at low temperature. It is believed that similar mechanism of diffusion of holes can also explain the viscosity of mineral glasses.
Synthesis and cyclopolymerization of 4,4‐dimethyl‐1,6‐heptadiene‐3,5‐dione
Authors: De Winter W. , Marvel C. S. 
Published: April 2003

AbstractDimethyldiacrylylmethane has been synthesized and polymerized to yield a soluble polymer which has the cyclic 1,3‐diketone structure. It has not been possible to prepare a polydioxime of this polyketone, but a monooxime with only 90% oximated structure was obtained. This monooxime underwent the Knoevenagel reaction to yield a partial ladder polymer which had interesting thermal stability.
Study of the preparations of a piperazine polyurea and polyamide by low temperature solution polymerization
Authors: Kwolek Stephanie L. 
Published: April 2003

AbstractThe preparations of two condensation polymers by low temperature solution polymerization are compared for the effect of reactant imbalance upon molecular weight. In addition, other variables, such as solvent selection, reaction time, and stirring rate are examined. The polymers are the polyamide from trans‐2,5‐dimethylpiperazine and terephthaloyl chloride and the alternating polyurea from trans‐2,5‐dimethylpiperazine and methylene bis(4‐phenyl isocyanate). In contrast to the polyamide‐forming reaction, the polyurea polymerization does not require acid acceptors and produces no by‐products. The investigation led to the preparation of extremely high molecular weight polyureas by use of the inert solvent mixture, tetramethylene sulfone–chloroform. Poly(N,N,‐terephthaloyl‐trans‐2,5‐dimethylpiperazine) was previously shown to have an unusual lack of sensitivity to reactant imbalance as compared to melt polycondensation when excess diamine was used as the acid acceptor. Similar behavior is found for the polyurea as well as the polyamide when tertiary amine is used as the acid acceptor. However, under certain conditions, side reactions can cause the formation of polyamides with lower inherent viscosity values than calculated. In both cases the insensitivity to reactant imbalance is ascribed to an extremely fast reaction.
Dependence of the glass transition temperature of polyacrylonitrile on molecular weight
Authors: Beevers R. B. 
Published: April 2003

AbstractThe glass transition temperature of polyacrylonitrile has been determined for polymer varying in molecular weight from 8 × 103 to 3 × 106. Results could be represented by Tg = (96.5 ± 1.0) − (2.8 ± 0.1) × 105/M̄n, giving for the glass temperature of a polymer of infinite chain length, 96.5 ± 1.0°C. Specimens showing coloration gave enhanced glass temperatures attributable to the stiffening effect of conjugated ring structures, and were excluded from consideration of the effect of molecular weight. Determination of Tg were made on films prepared from solutions of polymer in dimethylacetamide, butyrolactone, and dimethyl sulfoxide in addition to dimethylformamide. Dependence on weight percentage of polymer, w2, for the range 90 < w2 < 100 was given by Tg = (3.19 ± 0.03)w2 − (232 ± 4), no specific solvent effect being observed.
Polymerization of conjugated trienes
Authors: Bell Vernon L. 
Published: April 2003

AbstractThe polymerization of 1,3,5‐hexatriene, 1,3,5‐heptatriene, and 2,4,6‐octatriene with a variety of catalysts established the trienes as a distinct class of monomers which lead to unique unsaturated polyolefins. Soluble, high molecular weight polymers with predominantly 1,6‐enchainment were prepared with a soluble coordination catalyst system; this mode of polymerization resulted in 1,3‐dienyl groups in the polymer backbone. A stereospecific 1,6‐polyhexatriene, with a novel type of crystallinity based on trans, trans‐1,3‐diene repeat units, was prepared by low temperature polymerization with a vanadyl trichloride–triisobutylauminum catalyst.
Studies of the reduction of titanates and alkoxytitanium(IV) chlorides by alkylaluminum chlorides
Authors: Moyer Patricia H. 
Published: April 2003

AbstractReplacement of up to two of the chloride ligands on titanium tetrachloride with isopropoxy or butoxy groups results in an increase in the rate of reduction by alkylaluminum chlorides. The final product is still a titanium(III) compound. A decrease in rate results from replacement of more than two of the chloride ligands by alkoxy, or of the chloride ligands on aluminum by alkoxy. Exchange of alkoxy between titanium and aluminum occurs concurrently with reduction. These observations are explained in terms of the relative ease of replacement of a ligand on titanium by alkyl and the relative stability of the alkyltitanium compounds formed.
An infrared structural study of fluorocarbon polymers
Authors: White Horace F. 
Published: April 2003

AbstractThe 3μ infrared spectra of copolymers of ethylene and 1,1‐difluoroethylene with chlorotrifluoroethylene have been investigated. By applying “dilute solution” techniques, models for head‐to‐head and head‐to‐tail polymers have been prepared and spectrally characterized. The model spectra have been used to explain the polymerization of homopolymers and copolymers of halogenated ethylenes.
Polyacrylonitrile prepared in ethylene carbonate solution. I. Kinetics at low conversion
Authors: Peebles L. H. 
Published: April 2003

AbstractThe kinetics of acrylonitrile polymerization initiated by azobisisobutyronitrile in ethylene carbonate solution were studied at 50 and 60°C. Under these conditions simple solution polymerization kinetics should apply. The initial rate of polymerization was determined by varying the amount of initiator and the monomer concentration. The reaction is found to be first‐order in monomer concentration and approximately 0.6‐order in initiator concentration. The free radical derived from ethylene carbonate (by abstraction of a proton by a growing chain) apparently can only react with a monomer to start another polymer chain. It does not enter into termination reactions. That is, the solvent acts only as a transfer agent and a diluent and does not affect the rate of polymerization by entering into other reactions. The transfer reactions are relatively unimportant (transfer to monomer is negligible: transfer to solvent is small) as indicated by a study of the degree of polymerization calculated from the intrinsic viscosity. Thus, quite high molecular weight polymer can be obtained. The reaction is first‐order to high conversion and is independent of the viscosity of the medium.
Polyacrylonitrile prepared in ethylene carbonate solution. II. Kinetics at high conversion
Authors: Peebles L. H. 
Published: April 2003

AbstractThe first paper in this series has shown that when acrylonitrile is polymerized in ethylene carbonate, the transfer‐to‐monomer reaction is negligible, and the solvent acts only as a diluent and as a transfer agent. Furthermore, the rate of polymerization is first‐order to quite high conversions, even though there is a concomitant high viscosity of the polymerization media. These observations permit calculation of the effect of conversion on the average molecular weight of the polymer. The constants of this calculation were evaluated from low conversion polymerizations and applied to the case of high conversion. The measured weight‐average molecular weights as a function of conversion agree with the calculation and indicate that transfer‐to‐polymer reactions are probably very small. Hence, the extent of branching in polyacrylonitrile prepared in solution is also very small even at high conversions.