bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isopiestic method for determining molecular weights of polymers
Authors: Parrette Richard L. 
Published: April 2003

AbstractThe methods generally used for determination of the molecular weight of polymers usually cannot be used for molecular weights between 1000 and 30,000. This is the range most suitable for determination by the isopiestic method, whereby the molecular weight is measured by comparing the vapor pressure of the polymer solution with that of a solution containing a reference solute. The isopiestic principle can be adapted to polymers if the high degree of dependence of solute and solvent activities upon concentration can be evaluated. This is easily accomplished by plotting the reciprocal of the apparent molecular weight against the concentration and making an extrapolation to infinite dilution. Certain modifications of the conventional isopiestic techniques are necessary in order to accelerate the attainment of isopiestic equilibrium and to eliminate water from the solutions. Isopiestic equilibrium is readily attained if a proper combination of solvent and temperature is chosen, and if the solutions are agitated adequately. Water may be removed by the use of a drying agent in the solutions, although the drying agent causes minor errors which are difficult to correct. Results obtained with the isopiestic method show that it is reliable for molecular weights up to 40,000. The accuracy decreases rapidly with higher molecular weights.
Mechanism of emulsion polymerization of styrene with persulfate as activator in the absence and presence of mercaptan and a retarder
Authors: Kolthoff I. M. , O'Connor P. R. , Hansen J. L. 
Published: April 2003

AbstractWith the use of persulfate containing radioactive sulfur it is shown that the termination reaction of the polymerization of styrene is a coupling of the free radical chains. In the presence of m‐dinitrobenzene as a retarder evidence has been presented that the termination reaction is a disproportionation and not a combination of two free radical chains. Mercaptan in the emulsion polymerization of styrene acts solely as a chain transfer agent. Any chemical reaction between persulfate and mercaptan does not contribute to the initiation. In the presence of detergent the rate of initiation of the polymerization of styrene is equal to the rate of thermal dissociation of persulfate:

Thus, any reaction between persulfate with monomer and detergent does not contribute to the initiation. The much smaller rate of initiation in the absence of detergent is attributed to the slight solubility of styrene, the concentration of the monomer being so small that it cannot capture all the free radicals. The effect of the detergent is a physical one, by its solubilizing action it increases the solubility of the monomer in the water layer to such an extent that the “activator” now becomes 100% efficient.
Vinyl polymerization. IV. Influence of dimethylaniline on solution polymerization of vinyl chloride catalyzed by benzoyl peroxide
Authors: Imoto Minoru , Otsu Takayuki , Kimura Ko 
Published: April 2003

AbstractIn the solution polymerization of vinyl chloride with benzoyl peroxide, it was found that the initial rate of the polymerization was remarkably increased by adding dimethylaniline, but that conversion became constant at lower conversion. It was observed that when the rate became constant the benzoyl peroxide was completely decomposed and the reaction could be reinduced by adding more benzoyl peroxide. On the basis of these results, it seems possible that the polymerization is instituted by the benzoate radical and not by the dimethylaniline radical as suggested by Horner. The benzoate radical is produced through the reaction of dimethylaniline with benzoyl peroxide. In view of such considerations, we postulate a reaction mechanism for the polymerization of vinyl chloride.
Une nouvelle classe de polymeres d'α‐olefines ayant une régularité de structure exceptionnelle
Authors: Natta G. 
Published: April 2003

AbstractLes propriétés exceptionnelles d'une nouvelle classe d'hydrocarbures macromoléculaires à structure linéaire obtenus par polymérisation d'α‐oléfines sont décrites. La haute température de fusion, la cristallinité élevée, la faible solubilité, les propriétés mécaniques spéciales de ces polymères sont attribuées à une régularité particulière de structure due à l'existence, dans chaque macromolécule, de longues successions ordonnées d'atomes de carbone asymétriques ayant la même configuration stérique. Pour ce type particuler d'ordonnement d'atomes de carbone asymétriques dans des macromolécules linéaires, on propose le terme “isotaxique.”
The melting points of chain polymers
Authors: Bunn C. W. 
Published: April 2003

AbstractThe molecular characteristics which determine the melting points of high polymer crystals are considered, and it is shown that the properties of monomeric crystals often throw light on those of the polymers. The principal factors controlling melting points appear to be molar cohesion energy (of the whole molecule for monomers, or per chain unit for polymers), molecular flexibility (due to rotation round bonds), and molecular shape effects. Figures for the cohesion energy increments of a number of chain units and substituent groups are given, and melting points of polymer series are correlated with cohesion energy per chain unit. The flexibility factor is less easy to assess; barriers to rotation in appropriate monomer molecules are relevant, but available data are very rough. The approach therefore is mainly by empirical and comparative methods. When plotted against cohesion energy per chain unit, the melting points of various series of aromatic polyesters and polyurethans fall within the same band, while those of the polyamides lie on the whole higher and those of the aliphatic polyesters, polyethers, polythioethers and polydisulfides much lower. The differences are attributed to difference of molecular flexibility arising from the presence of easily rotating OC, SC and SS bonds. The low melting points of rubber and other unsaturated polymers are attributed to the fact (which can now be regarded as definitely established by independent evidence) that rotation round single bonds which are adjacent to double CC bonds is easier than in saturated chains. Easily rotating bonds which are inclined to each other, as in cis isomers, confer greater chain flexibility than the parallel bonds in trans isomers, and thus lead to lower melting points. The marked odd‐even effects in saturated molecules which run through the whole of organic chemistry (the even members always melting higher than the odd) are attributed to similar effects arising from the fact that the end bonds of an odd CH2 sequence are inclined to each other while those at the ends of an even sequence are parallel.
Preparation of graft copolymers from autoxidized polystyrene derivatives
Authors: Metz Donald J. , Mesrobian Robert B. 
Published: April 2003

AbstractExperiments on the low temperature autoxidation of polystyrene and several alkylated derivatives of polystyrene in solution are presented. Whereas the benzoyl peroxide catalyzed oxidation of polystyrene in isopropyl benzene proceeds extremely slowly, the oxidation of a partially isopropylated polystyrene readily yields a stable polymeric hydroperoxide containing up to 3.5 hydroperoxide groups per 100 monomeric units. The repressed oxidizability of polystyrene as contrasted with isopropyl benzene or isopropylated polystyrene is suggested to arise from a steric inhibition of resonance. Experiments on the bulk polymerization of vinyl monomers using polymeric hydroperoxides are described, and the results compared with vinyl polymerization initiated by cumene hydroperoxide. The preparation of a graft copolymer by the redox‐emulsion polymerization of methyl methacrylate using an isopropylated polystyrene hydroperoxide is described.
Surface films of synthetic polypeptides
Authors: Mishuck E. , Eirich F. R. 
Published: April 2003

AbstractThree synthetic α‐polypeptides were spread on aqueous substrates from suitable molecular solutions, and the surface areas, pressures, compressibilities, etc. measured on a horizontal film balance. On pure water spreading occurred at the best in the form of condensed films, but on aqueous solutions spreading improves with the solute concentration, especially near saturation of lyotropic compounds such as urea or potassium thiocyanate. On such substrates molecular weights (MW) and surface areas (SA) can be calculated by means of a modified van der Waals' equation. The MW and SA obtained as a function of substrate nature are found to be functionally related. The conditions and assumptions under which such a relation may be used to decide on true MW's, and their pertinence for the above polypeptide data, are discussed. Di‐ and trivalent cations in the substrate are found to increase MW's in accordance with their valence.
Apparent transfer constants of mercaptans in emulsion polymerization. I. Role of diffusion and distribution coefficients
Authors: Meehan E. J. , Kolthoff I. M. , Sinha P. R. 
Published: April 2003

AbstractThe chain transfer constants of normal and tertiary mercaptans with polystyrene radicals at 50°C. are, respectively, 19 and 4.5, with polybutadiene radicals, respectively, 19 and 3.7. The values are somewhat larger at 5°C., corresponding to an activation energy for transfer about 1 kcal./mole smaller than for propagation. At equilibrium 0.58 g. of n‐octyl, 0.62g. of tert‐octyl, 0.25 g. of n‐tetradecyl, and 0.26 g. of tert‐hexadecyl mercaptan can be dissolved per gram of polystyrene in emulsion, but the rate of attainment of equilibrium is extremely slow with the higher molecular mercaptans. The small apparent transfer constants of the higher mercaptans in emulsion polymerization are due to the slow rate of transport to the polymer particles. This transport is greatly accelerated by the addition of alcohol, which makes the distribution toward the water layer more favorable. In general the solubility in water of the mercaptan (or modifier in general) is the most important factor, the diffusion coefficient being of only secondary significance in a comparison of compounds of approximately the same molecular weight.
Copolymerization characteristics of ethyl vinyl ether and its beta‐bromo and beta‐carbethoxy derivatives
Authors: Price Charles C. , Schwan Theodore C. 
Published: April 2003

AbstractThe copolymerization of ethyl vinyl ether with acrylonitrile leads to values of the copolymerization parameters of Q = 0.06 and e = −0.8. Calculations from other data in the literature suggested that Q = 0.015 and e = −1.6 are better values. Copolymerization of β‐bromovinyl ethyl ether with styrene and methyl methacrylate indicates Q = 0.014 and e = 0.35. For ethyl β‐ethoxyacrylate, copolymerization with styrene and acrylonitrile indicates Q = 0.015 and e = 0.3. Both substituted vinyl lethers showed a much lower reactivity (Q factor) than expected. The decreased resonance interaction in these molecules was further supported by infrared data. Attempts to prepare β‐chlorovinyl methyl ether by three different methods were unsuccessful.
Report on molecular‐weight measurements of standard polystyrene samples. II. International union of pure and applied chemistry
Authors: Frank H. P. , Mark H. F. 
Published: April 2003

AbstractAs an extension of our original program, one more polystyrene fraction was investigated in numerous laboratories by means of viscosimetry, osmometry, light scattering, and ultracentrifuge. The various results are compared and critically discussed. Possible explanations and suggestions for improvement are offered in those cases in which considerable discrepancies occur. The viscosity results show satisfactory agreement. The discrepancies among osmotic results are believed to be due largely to unsatisfactory performance of the so‐called semipermeable membranes. Discrepancies among light‐scattering results can mostly be traced back to the unsatisfactory state of the various calibration techniques. The results obtained with the ultracentrifuge agree quite satisfactorily.
The scattering of light from thin polymer films. I. Experimental procedure
Authors: Stein R. S. , Keane John J. 
Published: April 2003

AbstractThe measurement of the scattering of light by solid polymers is a means for studying their structure. Films are the most convenient form for working with highly scattering polymers, which are subjected to such treatment as temperature variation, mechanical deformation, and orientation. In measuring scattering from films, it is necessary to correct the observed scattered intensity for (a) refraction at film interfaces, (b) reflection, and (c) secondary scattering. The necessary correction factors are described in this paper. The application of these correction factors is illustrated in the case of scattering by a polyethylene film.
Hydrogen peroxide as initiator in vinyl polymerization in homogeneous system. I. Kinetic studies
Authors: Nandi Uma Sankar , Palit Santi R. 
Published: April 2003

AbstractThe kinetic study of the polymerization of methyl methacrylate initiated by hydrogen peroxide in toluene, ethyl acetate, and methyl ethyl ketone as well as in bulk has been made. It has been established that the catalyst has no inhibition period and follows the square root relation. The initiation order is unimolecular with respect to the monomer in the fist two solvents and is half‐molecular with respect t o methyl ethyl ketone. The value of Δ (= κ/κp) for methyl methacrylate a t 60°C. a t various concentrations in the three solvents has been measured and found to remain sensibly constant and its value is 8.43. From bulk polymerization data the value of Δ at temperatures of 50, 60, 80, and 115°C. has been determined and they are 11.62, 8.43, 5.26, and 2.48, respectively. The temperature variation of Δ, and hence the corresponding energy of activation (Ep − 1/2Et), has also been measured and its value is found to be 5.71 kcals. The initiation constant under a variety of conditions has been determined by two independent methods (kinetic and DP) which have been found to yield values in fairly good agreement with each other, leading to a strong support to the usually assumed mechanism of polymerization. However, the initiation constant is found to change considerably with monomer concentration and change of solvent.
Viscosity, diffusion, and sedimentation of polyacrylonitrile solutions
Authors: Bisschops J. 
Published: April 2003

AbstractIntrinsic viscosity measurements of polyacrylonitrile fractions in dimethyl formamide at 25°C. and molecular weight determinations by the sedimentation‐diffusion method led to the following relation :

equation image

The data are consistent with the model of a coiled chain, impenetrable to the solvent, in agreement with the theories of Flory and co‐workers. The influence of the concentration upon the sedimentation constant was interpreted by an extension of the concept of the equivalent hydrodynamic sphere to the range of small finite concentrations. The following relation was thus obtained:

equation image

K should be a universal constant and its value is about 1.6 for most flexible polymers.
Determination of molecular weight of polyvinylpyrrolidone. II
Authors: Levy Gabor B. , Frank H. P. 
Published: April 2003

AbstractAdditional polyvinylpyrrolidone samples of great homogeneity have been prepared, and their intrinsic viscosity and molecular weight (by light scattering) have been determined in water and chloroform. In view of the new results the previous data were reinterpreted particularly with respect to the shift in K (in [η] = KMα) with homogeneity. All data were evaluated by objective statistical techniques and revised intrinsicviscosity molecular weight equations are proposed.
Effect of loss of low molecular weight polymers on molecular weight averages
Authors: Valentine L. 
Published: April 2003

AbstractThe effect of loss of low molecular weight species on the number and weight average molecular weights of polymers has been calculated for the main molecular weight distributions found for synthetic linear polymers. The expressions derived indicate that such an effect is most likely to be important for polycondensations and vinyl polymerizations propagated by monoradicals and terminated by transfer or disproportionation. Number average degrees of polymerization are much more liable to be seriously in error due to this factor than are weight average degrees of polymerization.
On the measurement of polymerization rates by means of infrared absorption spectra
Authors: Slowinski Emil J. , Claver George C. 
Published: April 2003

AbstractMeasurements have been made of the rate of thermal polymerization of styrene by observation of the infrared absorption spectrum of polymerizing samples in infrared absorption cells at 100°C. No effect of cell thickness on polymerization rate was noted, and the rate obtained agrees well with previously published values. An infrared method for determination of residual styrene monomer in polystyrene is described, and its possible application to rate studies on systems at high per cent conversion is noted.
The spherulitic structure of crystalline polymers. Part I. Investigations with the polarizing microscope
Authors: Keller A. 
Published: April 2003

AbstractAn investigation on polymer spherulites is being described in three parts. Part I (the present paper) describes the various effects observed under the polarizing microscope. These are interpreted in terms of the concepts of crystal optics; the problem of the position of the molecules and that of the microscopic fine structures will form Parts II and III. The materials examined were: polyethylene terephthalate, polyhexamethylene sebacamide and adipamide, and polyethylene. It is confirmed that the growing spherulites are a crystalline part of the crystallizing melt, and their individuality is demonstrated. The spherulites are radiating fibrous structures and the various observed extinction effects were interpreted in terms of such fibrous units. These extinction effects varied with the different materials and also for a particular substance with conditions of crystallization. Apart from the usual Maltese crosses, zigzag and ringshaped extinction lines were observed between crossed Nicols. The zigzag lines were interpreted as resulting from the index ellipsoids lying along elongated helical paths, while the most plausible explanation of the rings is given by closely coiled or strongly twisted arrangements of the index ellipsoids. The possibility of the existence of helical structures in spherulites is discussed in the light of earlier work on spherulites of simple substances.
Effect of electric field on light scattering of solutions of polar chain polymers
Authors: Isihara Akira , Koyama Ryuzo , Yamada Nobuo , Nishioka Atsuo 
Published: April 2003

AbstractThe effect of strong uniform electric field on the statistical configuration and the light scattering of linear chain polymers in solutions is studied. The statistical configuration of linear chain molecules is affected by the mutual interactions between the dipoles attached to the segments of the molecules and the external electric field. The radial distribution function of molecular segments from arbitrary chosen segment and that around the center of gravity of the molecule are calculated. The distribution functions are not spherically symmetric, and show that the molecules are slightly stretched toward the applied electric field. Using the radial distribution function calculated, we calculated the angular distribution of the intensity of scattered light by the deformed chain molecules. The intensity of scattered light is dependent on the magnitude of the applied electric field and the relative orientation of the incident ray, scattered ray, and electric field. Several special cases are illustrated. The effect of electric field is most conspicuous when the incident ray is parallel to the electric field and the scattered angle is 180°. We observed the effect of electric field on the light scattering of polyvinyl chloride molecules in diethylene oxide at the field intensity of 3000 v./cm. and the concentration 1%.
The spherulitic structure of crystalline polymers. Part II. The problem of molecular orientation in polymer spherulites
Authors: Keller A. 
Published: April 2003

AbstractThe orientation of the crystallites in spherulites was investigated by using special microbeam x‐ray techniques. The materials studied were: polyhexamethylene adipamide and sebacamide, polyethylene, and polyethylene terephthalate. In all these substances the c axes (molecular chains) were perpendicular to the radii of the spherulites, with some deviation from strict perpendicularity in the case of polyethylene terephthalate. The particular orientation of the crystallites around their c axes was in full agreement with the observed sign of birefringence, in the positive and negative polyamide spherulites, in polyethylene (where the indirect deduction made in earlier works has also been confirmed), and in the negative spherulites of polyethylene terephthalate. In the positive polyethylene terephthalate spherulites, while a fit between x‐ray results and birefringence might still be possible, it is somewhat doubtful whether the sign of birefringence could be accounted for by the crystallite orientation alone. The possible arrangements of the crystallites is discussed and it is suggested that the picture of closely coiled helices with the molecules lying along the winding direction might offer the most satisfactory explanation.
Polymethyl methacrylate: Dilute solution properties by viscosity and light scattering
Authors: Chinai S. N. , Matlack J. D. , Resnick A. L. , Samuels R. J. 
Published: April 2003

AbstractA polymethyl methacrylate polymer, prepared by the emulsion technique, was fractionated three times to obtain essentially homogeneous fractions. The intrinsic viscosities and weight average molecular weights were determined in an ideal solvent at 23°C. and in nonideal solvents at 25°C. The constants K and a in the conventional modified equation [η] = KMa were determined. The intrinsic viscosity in an ideal solvent was found to fit closely over the molecular range studied with the relation [η]θ = KM1/2. Light scattering measurements giving root‐mean‐square distance between ends of a polymer chain were carried out. It was shown that these results support both Kuhn's relation (r̄2)1/2 ≈︁ M0.50 and Flory's relation (r̄2)3/2 = M[η]/2.1 × 1021 in an ideal solvent. In a nonideal solvent only Flory's relation was found to be in agreement with the experimental results. The values of volume expansion factor α3 ratios A2M/(r̄2)3/2 and A2Mw/[η] in a nonideal solvent and the value of the ratio [η]/M1/2 in an ideal solvent showed that the polymer molecules were expanded beyond their random flight dimensions in a nonideal solvent.
Linear polyesters derived from vanillic acid
Authors: Bock Louis H. , Anderson James K. 
Published: April 2003

AbstractVanillic acid, which is potentially available from lignin, was converted to dibasic acids by etherifying the phenolic hydroxyl group with alkylene dihalides. The dibasic acids were esterified with ethylene glycol and condensed to linear polyesters. The polyesters were converted to fibers by melt spinning. The fibers could be stretched, preferably in a warm water bath, to give fibers with good tenacity and increased crystallinity as shown by birefringence measurements. The polyester obtained from ethylenedivanillic acid melted at 210°C. but softened and shrank at 80°C.