bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some kinetic effects in the polymerization of 1,3,5‐trioxane
Authors: Kern W. , Jaacks V. 
Published: April 2003

AbstractThe cationic polymerization of 1,3,5‐trioxane in methylene dichloride with boron trifluoride, producing polyoxymethylene, was investigated. An ionogenic cocatalyst is not required in this polymerization. During the induction period, initially formed, short polyoxymethylene chains depolymerize to formaldehyde until a constant equilibrium concentration of formaldehyde is reached. This concentration is equal to the ceiling concentration of formaldehyde in cationic polymerization under the conditions chosen for the experiments. The nonstationary state and the strong acceleration of the polymerization of trioxane are due mainly to the lack of an effective kinetic termination reaction. Thus the concentration of growing polyoxymethylene cations increases with time.
Contribution purement chimique à la connaissance de la forme des macromolécules en solution
Authors: Loucheux Marie‐H. , Banderet A. 
Published: April 2003

AbstractL'étude cinétique de l'aminolyse de la fonction anhydride nous a permis de préciser l'influence de la chaîne macromoléculaire sur la réactivité d'un groupe fonctionnel. La stoechiométrie de cette réaction a été établie sur des micromoléculcs. La vitesse de la réaction est suivie par spectroscopie ultra‐violette; il s'agit d'une réaction bimoléculaire catalysée par l'acide formé. Dans le cas où la fonction anhydride est seule sur une chaîne marcromoléculaire, elle réagit avec la même vitesse que l'anhydride butyrique. Mais pour les polyanhydrides que nous avons utilisés (obtenus par copolymérisation de l'anhydride maléique et dn méthacrylate de méthyle), la vitesse de réaction, comparée à celle de l'anhydride succinique, est très faible. Nous tentons d'expliquer cette différence par la faible solubilité des groupes anhydrides dans le benzène: la chaîne de PMM formerait écran autour des groupes anhydrosucciniques, qui, moins solublcs, se rassemblent au milieu de la pelote macromoléculaire.
New methods of modifying the properties of cellulose
Authors: Rogovin Z. A. 
Published: April 2003

AbstractThe chief scientific trends worked out in the laboratory of the author concerning the problems of modifying cellulose have been considered. Special attention is given the following: (1) synthesis of new cellulose ethers and esters, (2) the introduction of new functional groups into the cellulose macromolecules, and (3) the synthesis of graft copolymers of cellulose.
The influence of monomer concentration and diluents on the polymerization of isobutene
Authors: Kennedy J. P. , Thomas R. M. 
Published: April 2003

AbstractThe relation existing between monomer concentration and degree of polymerization of polyisobutenes obtained in various diluents with AlCl3 catalyst has been investigated at −78°C. Methyl chloride, ethyl chloride, methylene chloride, vinyl chloride, and n‐pentane were used as diluents. It was demonstrated that the DP increases with decreasing monomer concentration irrespective of the investigated polymerization medium. A hypothesis which could explain the experimental facts is presented. The influence of dielectric constant on the molecular weight of polyisobutene has been studied in methyl chloride—carbon disulfide mixtures. The seeming contradiction existing between experimental findings and expectation based on older theories has been resolved by the introduction of “effective D.C.” theory. The “lifetime” of carbonium ions and the “temperature build‐up” in the fast low‐temperature polymerization has been estimated.
The chemistry of xylylenes. X. Some polymers and telomers of spiro‐di‐o‐xylylene
Authors: Errede L. A. 
Published: April 2003

AbstractSpiro‐di‐o‐xylylene polymerizes via a free‐radical mechanism to give high molecular weight poly(o‐xylylene). It reacts with olefinic molecules, such as styrene, acrylonitrile, methyl methacrylate, vinylidine fluoride, and butadiene to give copolymers containing di‐o‐xylylene units in its backbone. Solutions of spiro‐di‐o‐xylylene can be titrated with iodine, and di‐o‐xylylene‐di‐iodide is produced stoichiometrically. Telomers of di‐o‐xylylene are obtained when the spiro compound is allowed to react in the presence of chain transfer agents such as HSR and CBr4.
Polyethers. XII. Poly‐(2,6‐disubstituted‐1,4‐phenylene oxides)
Authors: Kurian C. J. , Price Charles C. 
Published: April 2003

AbstractA number of poly(p‐phenylene oxide) polymers have been prepared from 4‐bromophenols with various combinations of methyl, propyl, allyl, and phenyl groups in the 2,6‐positions. Potassium ferricyanide, lead dioxide, and 2,4,6‐tri‐tert‐butylphenoxy radical have been used as initiators. The reactions proceed to higher molecular weights under nitrogen. These polymers are soluble resins of low molecular weight, softening somewhat above 100°. Those with allyl groups become insoluble and infusible on exposure to air for several days.
Critical conditions for the formation of infinite networks
Authors: Khan Allan 
Published: April 2003

AbstractThe general expression for determining the critical point in the condensation of mixtures of A‐monomers of varying functionality with mixtures of B‐monomers of varying functionality has been obtained utilizing the assumptions made by Flory in his early work on the formation of infinite networks. It is shown that at the critical point, pApB = 1/[(f′ – 1)(g′ – 1)] where pA and pB are the respective probabilities that an A or B group has reacted, and f′ and g′, respectively, give the average functionality of A and B.
The mechanism of the anionic polymerization of methyl methacrylate. II. The use of molecular weight distributions to establish a mechanism
Authors: Glusker Donald L. , Lysloff Irene , Stiles Elise 
Published: April 2003

AbstractCalculations of the molecular weight distribution to be expected from a nonterminated polymerization in which the rate of initiation is rapid with respect to that of propagation predict that the weight‐ to number‐average molecular weight ratio should approach 1.0. The ratios actually obtained are considerably larger than the predicted value; the resolution of this apparent contradiction is the central problem of this paper. Fractionation of isotactic poly(methyl methacrylate) was accomplished by a combination of two techniques: liquid‐liquid counter‐current extraction and elution chromatography. The fractionation indicated that: (1) The molecular weight distribution of these polymers is bimodal. (2) More than 90 mole‐% of the polymer chains has a molecular weight less than 2000. (3) These low molecular weight chains add tritium upon reaction with tritiated acetic acid and do not therefore result from irreversible termination reactions. (4) The molecular weight distribution of the high molecular weight material separated by elution chromatography is sufficiently broad to approximate a log‐normal distribution. (The log‐normal distribution is commonly used to characterize linear polyethylenes, which have very broad molecular weight distributions.) Kinetics were measured in a 90% toluene‐10% diethyl ether by volume mixture at −60°C. These experiments showed that: (1) The rate of polymerization appears to be first order in monomer and remains constant to very high conversion of monomer to polymer. (2) Plots of –In M/M0 versus time (where M and M0 represent monomer concentration at time t and 0. respectively) can be extrapolated to a finite conversion intercept at zero time. (3) This conversion corresponds to that required to form a species containing one fluorenyl group and three monomer units. (4) Plots of number‐average molecular weight versus time converge to the same intercept at zero time, regardless of the ratio of initial concentration of monomer to that of initiator, and that intercept is the molecular weight of the species just mentioned, FlM3. The mechanism which has been derived from these data has the following essential postulates: (1) Chains of different steric configurations may propagate at different rates even in a homogeneous medium. (2) A high percentage of the total number of chains started undergoes a “pseudotermination” whose probability is a function of the configurations of the last three monomer units in the chain. (3) When a chain attains a minimum length of 8–10 monomer units, the probability that further additions will take place in isotactic sequence is greatly increased. (4) The source of this increased probability is thought to lie in the inherent asymmetry of preferred helical conformations which may exist for chains of this minimum length in solution at −60°C.
Color and radical formation in irradiated polyvinyl chloride
Authors: Atchison G. J. 
Published: April 2003

AbstractWhen polyvinyl chloride is irradiated with high energy radiation a visible color change varying through green‐yellow to deep red‐black is produced, depending upon the dose and temperature. Spectrophotometric and electron spin resonance techniques were used to investigate the formation of colored material by 2‐m.e.v. electron irradiation of unplasticized polyvinyl chloride moldings. The observed chemistry of the colored material is in agreement with the postulations of earlier workers that colored polyene structures are formed. Three radiation‐produced free radicals decaying at room temperature with half‐lives of 4.5, 63, and 1630 hr. were observed. The color in the 550 mμ region was found to be inversely proportional to the concentration of the long‐lived radical. The presence of absorption maxima in the 350–500 mμ region was observed in irradiated moldings and in tetrahydrofuran solutions of irradiated moldings.
Polymerization of phenyl‐substituted butadienes by metal alkyl catalysts
Authors: Stille J. K. , Vessel Eugene D. 
Published: April 2003

AbstractHeterogeneous Ziegler‐type catalysts polymerize 2‐phenyl‐1,3‐butadiene to form low molecular weight polymers. The polymer prepared with a 3:1 catalyst ratio of aluminum triisobutyl to titanium tetrachloride contains 80–90% cis‐1,4‐units and the polymer formed by the 1:1 catalyst has 60–70% cis‐1,4‐structure. No trans‐1,4‐ or 3,4‐units are found in any of the polymer samples and the remaining unsaturation is attributed to 1,2‐polymerization. Both Ziegler‐type catalysts and butyllithium are ineffective for the polymerization of 2,3‐diphenyl‐1,3‐butadiene.
Microscopic studies of Mylar film and its low molecular weight extracts
Authors: Giuffria Ruth 
Published: April 2003

AbstractMylar polyester film has some low molecular weight material which may be extracted by various organic solvents as well as oil. This extract crystallizes in different crystal forms depending upon conditions of crystallization. Regardless of the crystal form, the Mylar extracts act alike on a hot stage, subliming without melting at 300°C. to form a sublimate which will melt sharply at 322°C. This characteristic behavior, as well as its crystallization from chloroform, forms a basis for microscopic identification of very small quantities of low molecular weight Mylar. The presence of a sublimate of low molecular weight material from raw Mylar film and the complete absence of any sublimate from extracted Mylar film makes possible rapid differentiation between raw and extracted films. This sublimate has characteristics similar to those of low molecular weight material obtained by solvent extraction. There exist in Mylar film minute areas of different refractive index which make a definite contribution to the haze level of the film. These areas are assumed to be different in crystallinity than the matrix in which they exist.
Polymer fractionation by precipitation chromatography
Authors: Jungnickel J. L. , Weiss F. T. 
Published: April 2003

AbstractThe precipitation chromatography method of Baker and Williams has been found to have advantages in efficiency and ease of operation over other methods for fractionation of polymers. Good fractionations according to molecular weight have been obtained on several polymers of widely different molecular weight distributions, including samples of polystyrenes and of a high molecular weight polyolefin.
Studies on amylose and its derivatives. Part II. Light‐scattering and viscosity studies on amylose acetate in dilute solution
Authors: Cowie J. M. G. 
Published: April 2003

AbstractAmylose acetate has been fractionated and the solution properties of the fractions studied in two solvents. Weight‐average molecular weights have been determined in nitromethane by the light‐scattering method, and measurements of viscosity as a function of shear stress have been made in chloroform and nitromethane. The Ree‐Eyring flow theory has been used to describe non‐Newtonian behavior which was detected in samples with [η] > 2.0. The parameters in the Mark‐Houwink equation are [η] = 1.10 × 10−5M̄0.87 in CH3NO2 and [η] = 1.06 × 10−5M̄0.92 in CHCl3. The Kratky‐Porod chain model has been found to be most useful in describing the hydrodynamic behavior and indicated that the molecule is much stiffer than the vinyl polymers but more flexible than the cellulose derivatives. The existence of a helical form has been discussed, and it is thought probable that this is the basic form in solution.
Sorption and diffusion in crystalline elastomers. Part I. Solubility of isomeric hydrocarbons in stretched rubber
Authors: Barrie J. A. , Platt B. 
Published: April 2003

AbstractThe solubility coefficients of n‐ and isobutane for stretched crosslinked natural rubber have been measured for simple elongations of 0–400% in the temperature range 30–50°C. To minimize the effect of penetrant on the degree of crystallinity, regions of low concentration were chosen. The sorptive capacity of the rubber was not significantly altered by elongation until the extension was sufficient to permit crystallization to take place. For both stretched and unstretched samples temperature—hysteresis effects were absent and Henry's law was obeyed. The data indicate that the difference in solubility between stretched and unstretched rubber can be taken as a measure of the degree of crystallinity. A slight decrease in the solubility over extended periods of time was attributed to a corresponding slow increase in the degree of crystallinity. The dependence of the degree of crystallinity on temperature and elongation was well represented by that deduced from Flory's theory of strain‐induced crystallization.
A versatile osmometer for polymer gels and solutions with applications to cellulosic gels
Authors: Pennings A. J. , Prins W. 
Published: April 2003

AbstractAn osmometer is described which is capable of measuring swelling pressures of polymer and polyelectrolyte gels up to 200 atm., as well as measuring osmotic pressures of solutions down to approximately 0.1 mm. H2O pressure. For the latter, use can be made of the deswelling of a solvent swollen gel that occurs when it is placed in contact with the polymer solution. In this case no semipermeable membrane is required. Useful thermodynamic information regarding the network structure of gels can be obtained, which in the case of polyelectrolytes cannot be obtained through vapor phase measurements. Measurements on a gel obtained by crosslinking cellulose acetate in solution allow the determination of the elastic free energy and the degree of swelling q0 at which the coiling chains are relaxed, if Huggins' parameter in the expression for the free energy of mixing is known. If the degree of swelling q is not too far removed from q0, it is shown that the “rubber elasticity” theory of networks holds, and yields the number of crosslinks in the gel. Pressure measurements of a cellulose gel in water and in alkali solutions are presented. The maximum in the swelling pressure at 10% alkali is qualitatively explained with Neale's theory, which considers the cellulose hydroxyl groups to be weakly acidic.
Graft copolymers of p‐isopropylstyrene and methyl methacrylate
Authors: Matlack J. D. , Chinai S. N. , Guzzi R. A. , Levi D. W. 
Published: April 2003

AbstractThe preparation of a completely isopropylated polystyrene by polymerization of p‐isopropylstyrene monomer is described. This polymer was autoxidized in cyclohexane with lauroyl peroxide to give a material of good reproducibility and high purity. Methyl methacrylate was successfully grafted to the polymeric hydroperoxide by using a sugar‐containing recipe. Homopolymer was separated from the graft copolymer by extraction. Evidence for grafting was obtained from solubility and fractionation behavior, as well as from light‐scattering and viscosity measurements.
Second‐order transitions in solutions of cellulose triacetate
Authors: Sharples A. , Swinton F. L. 
Published: April 2003

AbstractThe system cellulose triacetate in chloroform has been studied using the technique of dilatometry, viscometry, and light‐scattering, and it has been observed that although under certain conditions the solutions can be induced to gel, gelation occurs without the change in volume to be expected for a first‐order transition. Two second‐order transitions have been observed however, which are still detectable while the system is in the liquid state. In addition, the transition temperatures have been found to be independent of concentration. An explanation for these unusual effects has been proposed, suggesting that the system contains submicroscopic, partly crystalline aggregates of polymer molecules, whole melting point lies above the temperature range studied. Gelation is considered to take place by a coalescence of these aggregates, and second‐order transitions to occur within the aggregates while the aggregates while the system is in an apparently liquid state.
Differential thermal analysis of high polymers. III. Polyamides
Authors: Ke Bacon , Sisko A. W. 
Published: April 2003

AbstractDifferential thermal analysis has been used to study melting and glass transitions in various homo‐ and copolyamides, as well as crystallite disorientation in nylon monofilaments. Transition temperatures obtained from the thermograms of the commoner polyamides agree well with literature values, but the less common polyamides gave slightly higher melting points. Heats of fusion of polyamides 66 and 610 were obtained from the thermograms by calibration with a calorimetric standard. These values together with the independently determined degree of crystallinity have been used to calculate the true heats of fusion. The thermograms of two series of copolyamides, the adipamide–sebacamides and adipamide–terephthalamides, showed changes in peak shapes, positions, and areas from those of the parent homopolymers. Decrease in crystallinity led to pronounced glass transitions. Two melting peaks observed for certain copolymers are interpreted as evidence for the production of block copolymers, which are favored by the reaction conditions existing in interfacial polycondensations.
Dynamic mechanical behavior of some partially crystalline poly‐α‐olefins
Authors: Woodward A. E. , Sauer J. A. , Wall R. A. 
Published: April 2003

AbstractInternal friction (Q−1) and dynamic elastic storage modulus have been measured as functions of temperature (80°K. and higher) for partially crystalline samples of poly(pentene‐1) (PP1), poly(3‐methylbutene‐1), (P3MB1), and poly(4‐methylpentene‐1) (P4MP1); a resonance technique at audiofrequencies was used. Two internal friction peaks at 145°K. (γ) and 290°K. (β) and a final upswing in Q−1 at 335–345°K. (α) in conjunction with associated modulus dispersions are exhibited by PP1, the mechanical loss spectrum being similar to that reported previously for poly(butene‐1) except that the final upswing for PP1 occurs at lower temperatures. Both P3MB1 and P4MP1 have small Q−1 damping peaks near 150°K. (γ). The latter polymer also has a peak of considerable magnitude at 335–340°K. (β) and an upswing in Q−1 at 425–435°K. (α). The former polymer shows a broad dispersion commencing at about 320°K. (β). Owing to the absence of a sizable transition below the principal amorphous transition starting at about 325°K., the modulus for P3MB1 exhibits the least variation with temperature in the range of 80–325°K. among the poly‐α‐olefins with aliphatic side chains, including polyethylene and polypropylene, that have been studied by this method. It is suggested that the γ and β loss peaks and associated modulus changes are the consequence of the onset of motion in the amorphous regions, involving small and large number of chain segments, respectively.
Copolymerization of 1‐acrylamido‐1‐deoxy‐Dhyphen;glucitol and of 1‐deoxy‐1‐methacrylamido‐D‐glucitol with various vinyl monomers
Authors: Whistler Roy L. , Goatley James L. 
Published: April 2003

AbstractCopolymerization characteristics for 1‐acrylamido‐1‐deoxy‐D‐glucitol and of 1‐deoxy‐1‐methacrylamido‐D‐glucitol with various vinyl monomers is given. For the former compounds Q and e values are found to be 0.12 and 0.6 respectively and, for the latter, 0.08 and 1.3. In addition, viscosity, osmotic molecular weights, and solubilities for representative compounds are given.
Molecular weight distribution and branching in butadiene polymers and copolymers
Authors: Cooper W. , Vaughan G. , Eaves D. E. , Madden R. W. 
Published: April 2003

AbstractButadiene polymers and copolymers prepared in emulsion and with complex coordination catalysts have been examined by use of light‐scattering, osmometric, viscometric, and fractionation techniques. These polymers are particularly prone to branching, the extent of which has been characterized from light‐scattering and viscometry data. A correlation was obtained between polydispersity and branching, and the lightscattering second virial coefficients of the polymers. The second virial coefficients obtained from osmotic pressure measurements were not greatly affected by the presence of branched polymer. Similar results were obtained on a butadiene–styrene copolymer which was branched by exposure to high energy radiation. Further branching, leading ultimately to crosslinking, occurred on storage of polybutadiene both in the solid polymer and in concentrated solution, the changes being influenced by catalyst residues in the polymer. On the other hand, in dilute solution or on milling in the presence of radical traps, degradation at the branch points occurred. No relationship was observed between branching and the physical properties of the polymer. Butadiene polymers prepared using complex coordination catalysts, possessed, in general, somewhat wider molecular weight distributions than emulsion polymers prepared at 10°C. They were characterized by substantial amounts of low molecular weight polymer and the absence of a high molecular weight tail. The molecular weight of essentially linear fractionated polybutadiene of 93% cis‐1,4‐ content is related to the intrinsic viscosity by [η] (benzene 100 ml. g.−1) = 1.00 × 10−4M0.77. After making corrections for differences in structure and chain stiffness this relationship is in close accord with relationships from other sources obtained on unbranched butadiene polymers.
Spherulites in nylon 610 and nylon 66
Authors: Lindegren C. R. 
Published: April 2003

AbstractThe two types of spherulites in nylon 610 differ in birefringence, melting point, and rate of growth. The rates of growth depend strongly upon the degree of supercooling, and—at least for the positive spherulites—to a small extent on the molecular weight. The rate curve for the positive spherulites has a singular point at 188°C. and appears to have a maximum in the neighborhood of 120°C. Concentric rings were observed in positive spherulites only after crystallization in the temperature range between 188° and 195°C. Positive spherulites formed near 180°C. have maximum birefringence. Negative spherulites were observed only in specimens allowed to crystallize between 205° and 225°C. Three types of spherulites were observed in nylon 66. The large, positive, and highly birefringent spherulites have the same melting point, 273—274°C., as the negative spherulites. The small positive spherulite with normal birefringence melt at 269.5—270°C. Simultaneous growth of all three types of spherulites was observed only between 250 and 255°C.