bluuebunny/crossref_metadata_2025_split huggingface dataset:
Emulsion polymerization of vinyl acetate. II
Authors: Litt M. , Patsiga R. , Stannett V. 
Published: April 2003

AbstractThe emulsion polymerization of vinyl acetate was investigated at low ionic strengths and has quite unusual kinetics. The rate of polymerization is dependent on the initiator concentration to the first power and independent of soap concentration. In seeded polymerizations, the rate of polymerization depends on initiator to the 0.8 power, particle concentration to the 0.2 power, and monomer volume to 0.35 power. In all cases the rate of polymerization is almost independent of monomer concentration in the particles until 85–90% conversion. These results were rationalized by the following mechanism: (a) polymerization initiates in the aqueous phase because of the solubility of the monomer and is stabilized there by adsorption of ionic soap on the growing polymer molecule; (b) the growing polymer is swept up by a particle at a degree of polymerization (under our conditions) of about 50–200. Growth continues in the particle. This sweep‐up is activation‐controlled as both particle and polymer are charged. (c) Chain transfer to the acetyl group of monomer gives a new small radical which cyclizes to the water‐soluble butyrolactonyl radical, and reinitiates polymerization in the aqueous phase; (d) the main termination step is reaction of an uncharged butyrolactonyl radical with a growing aqueous polymer radical. A secondary reaction at low ionic strength is sweep‐up of an aqueous radical by a particle containing a radical. At high ionic strength, this is the major termination step. The unusual kinetic steps are justified by data from the literature. They are combined with the usual mechanisms operating for vinyl acetate polymerization and kinetic equations are derived and integrated. The integral equations were compared with the experimental data and shown to match it almost completely over the whole range of experimental variables.
Calculation of the glass transition temperatures of polymers. Part I. Homopolymers and copolymers with alkyl side chains
Authors: Lee W. A. 
Published: April 2003

AbstractFour equations, relating the glass transition temperatures Tg of homopolymers and copolymers to invariant additive temperature parameters (ATP) associated with their constituent groups, but weighted in different ways, have been applied to the calculation of the Tg of seven series of polymers having alkyl side chains. It is shown that the Tg of the 32 polymers considered may be calculated, within 7°K of the observed values, without the use of interaction coefficients from 15 independent variables, representing summations of the ATP's. The present calculations are confined to those structures which may be formed by a recombination of the structures corresponding to these independent variables. It is an essential feature of the approach that a distinction is made between groups with different nearest neighbors. Alternative methods of calculation are considered. The temperature parameter for a sequence of three or more methylene groups is estimated as 141°K, in conformity with the transition in polyethylene at 148°K. Nearest‐neighbor interactions, stereoregularity, and crystallinity effects are discussed.
Hyperelectronic polarization, a physical property of EKA‐conjugated polymers
Authors: Wyhof J. R. , Pohl H. A. 
Published: April 2003

AbstractHyperelectronic polarization is a molecular mechanism which can produce very large dielectric constants in certain macromolecular solids. The present paper reports studies of the frequency, pressure, and temperature responses of this extreme polarization and related electronic conductivity on a variety of new polymers. The polymers studied were quinazone, metallo‐organic dithiooxamide type, and pyropolymers. The latter were examined in pure and in metal‐doped forms. Dielectric constants ranging from 10 to 500 were observed for the quinazone polymer, which was, incidentally, found to exist in two forms. Dielectric constants ranged from 30 to 100 for the metallo‐organic polymer from 25 to 10,000 for the pure pyropolymer and were of the order of 500 for a calcium doped pyropolymer. One set of nickel‐doped pyropolymers was found to conduct quite well (resistivity 76.8 × 10−6 ohm‐cm).
Simultaneous measurement of vapor diffusion and solubility coefficients in polymers by frequency response techniques
Authors: Evnochides S. K. , Henley E. J. 
Published: April 2003

AbstractAn experimental technique for the simultaneous measurement of solubility and diffusion coefficients in polymers by frequency response techniques has been developed. A sample of polymer suspended from an electrobalance is exposed to a permeating gas whose pressure is being varied sinusoidally at ultra‐low frequencies. The phase angle and amplitude of the weight changes are measured as a function of the frequency of the pressure wave. It is shown that in the linear range the diffusivity coefficient for polyethylene–ethane calculated from the phase angle lag and the Henry's law solubility and the diffusivity obtained from the amplitude ratios are in excellent internal agreement and also agree with values obtained from transient measurements.
Unit‐cell dimensions of bulk‐ and solution‐crystallized linear polyethylene
Authors: Kitamaru R. , Mandelkern L. 
Published: April 2003

AbstractThe unit‐cell dimensions and density, at room temperature, of bulk‐ and solution‐crystallized linear polyethylene have been determined. The macroscopic measured densities for the bulk‐crystallized samples ranged from 0.917 to 0.993 g/cc, and the lattice parameters were found to be independent of the sample density. In contrast, for solution‐formed crystals, despite the limited range in macroscopic densities that can be attained, there is a systematic variation in the a and b dimensions with the measured density and the crystallite thickness. The implication of these results for the calculation of the degree of crystallinity and the interpretation of certain infrared bands are discussed.
Small‐angle light scattering by random assemblies of incomplete spherulites. II. Truncated spherulites
Authors: Stein Richard S. , Picot Claude 
Published: April 2003

AbstractPrevious theoretical calculations of the scattering from spherulites are for isolated complete spheres, whereas most spherulitic polymer samples contain truncated spherulites as a result of impingement by other spherulites. The effect of such truncations on the scattering patterns for two‐dimensional spherulites is explored as a function of the size, number and location of the truncations. The scattering of severely truncated spherulites is modified, particularly with regard to the enhancement of the HV scattering at small angles. However, reasonable amounts of truncation corresponding to experimentally observed structures do not produce appreciable modification of the pattern so that the neglect of truncation will not lead to appreciable error in the estimated spherulite size from light scattering.
Characterization of cellulose acetates by nuclear magnetic resonance
Authors: Goodlett V. W. , Dougherty J. T. , Patton H. W. 
Published: April 2003

AbstractAn NMR method for determining the distribution of acetyl groups in cellulose acetates was developed. Treatment of cellulose acetates with acetyl‐d3 chloride gave products having simple spectra which could be analyzed quantitatively to give the distribution of acetyl groups in the original sample. The method was applied to studying (1) the hydrolysis of cellulose triacetate with ammonia, (2) the acetylation of cellulose acetate with acetyl chloride, and (3) the acetylation of cellulose acetate with acetic anhydride.
Radiation‐induced solid‐state polymerization of trioxane under high pressure
Authors: Yamazawa Yuzo , Iwai Tadashi , Ito Akihiko , Hayashi Koichiro 
Published: April 2003

AbstractThe in‐source polymerization of trioxane in the solid state was investigated over a wide range of temperature and pressure, i.e., from 30 to 140°C and up to 7000 kg/cm2, respectively. In the polymerization that was carried out slightly below the melting point under pressure, the higher the pressure, the higher the rate of polymerization. It was confirmed that the maximum rate of solid‐state polymerization of trioxane occurs near the melting points, even under elevated pressure. The rate of polymerization decreased with increasing pressure at constant temperature. The shape of the time–conversion curves may be classified into two types, i.e., one which is typical of high pressure and low temperature, and the other which is typical of low pressure and high temperature. Changes in the shape of the conversion—intrinsic viscosity curves occurred coincidentally. Thus, three regions for the different “polymerization characteristic” were determined as functions of polymerization temperature and pressure. Explanations are given for the above‐mentioned polymerization characteristic.
Orientation of polymer molecules during melt spinning. I. Estimation of degree of orientation by retraction above Tm
Authors: Furukawa Junji , Kitao Toshio , Yamashita Shinzo , Ohya Seigo 
Published: April 2003

AbstractThe elastic deformation ratio by spin‐stretching was estimated by means of thermal retraction technique, data for a melt‐spun filament from a crystalline polymer were compared with those from an amorphous one. The necessary conditions for equilibrium retraction were determined as 7 min at 170°C for amorphous polystyrene and 30 min at 180°C for high‐density polyethylene. The effects of molecular weight and melt draw ratio on the retraction behavior were discussed and concluded to be negligible. The apparent activation energies of viscous flow were calculated from the temperature dependence of the retraction curves. The activation energy for polystyrene decreases with increasing temperature of retraction, as predicted by the WLF equation, and that of polyethylene obeys Arrhenius law (about 12 kcal/mole). This may be attributed to the difference in glass transition temperatures of the two polymers. By measuring the effective melt draw ratio of the resultant filaments of different melt draw ratio, it was made clear that the elastic deformation increases with increasing apparent melt draw ratio. Finally, the optical anisotropy of the filaments was related to the deformation ratio. It was concluded that Kuhn and Grün's equation may be applicable for polystyrene but not for polyethylene.
Ladder pyrrolone structures with anthraquinone recurring units
Authors: Szita Jeno , Brannigan L. H. , Marvel C. S. 
Published: April 2003

Abstract1,2,4,5‐Tetraaminoanthraquinone and 1,4,5,8‐naphthalene‐tetracarboxylic acid dianhydride react in dimethylacetamide to give a tetrameric prepolymer with balanced endgroups of anhydride and diamine. When this prepolymer is carefully treated with polyphosphoric acid at elevated temperature it is converted to a soluble polypyrrolone type structure with an inherent viscosity of 2.3–2.7. Polymers of this molecular weight can be wet‐spun into pliable fibers from methanesulfonic acid. The TGA curve in air shows little weight loss below 550°C. The polymer can also be solubilized by reduction with sodium dithionite in alkaline aqueous dimethyl sulfoxide.
Polyaromatic pyrazines: Synthesis and thermogravimetric analysis
Authors: Higgins Jerry , Jones Joe F. , Thornburgh Allan 
Published: April 2003

AbstractThe syntheses of five polyaromatic pyrazine polymers are described. These polymers were synthesized by the condensation of bis‐α‐haloaromatic ketones with ammonia in N,N‐dimethylacetamide (DMAc) solvent in the presence of air or peroxides. The condensation of bis‐p‐(α‐bromoacetyl)benzene (IIIa), bis‐p,p′‐(α‐chloroacetyl)biphenyl (IIIb) bis‐p,p′‐(α‐chloroacetyl)diphenyl ether (IIIc), bis‐p,p′‐(α‐chloroacetyl)diphenylmethane (IIId), and α,α′‐dibenzoyl‐α,α′‐dibromo‐p‐xylene (V) under these reaction conditions gave poly[2,5‐(1,4‐phenylene)pyrazine] (IVa), poly[2,5‐(4,4′‐biphenylene)‐pyrazine] (IVb), poly[2,5‐(4,4′‐oxydiphenylene)pyrazine] (IVc), poly[2,5‐(4,4′‐methylenediphenylene)pyrazine] (IVd), and poly[2,5‐(1,4‐phenylene)‐3,6‐diphenylpyrazine] (VI), respectively. Thermogravimetric analysis (TGA) of these polymers showed them to be thermally stable up to the temperature range of 450–550°C in air for short periods of time. The inherent viscosities of these polymers ranged from 0.18 to 1.30.
Preparation and structure of chlorinated poly(vinyl flouride)
Authors: Bacskai R. , Lindeman L. P. , Adams J. Q. 
Published: April 2003

AbstractThe low‐temperature chlorination of poly(vinyl fluoride) (PVF) proceeds readily in CCl4 suspension. The rate of chlorination is high initially, but the reaction slows down considerably when the chlorine content of the polymer reaches 40–50%. At long reaction times, polymers containing 62% chlorine (1.88 chlorine atoms per monomer unit) can be obtained. As the degree of chlorination increases, the solubility of PVF in organic solvents increases. Polymer crystallinity and polymer softening point decrease with chlorination. Polymers containing 40% chlorine appear to be completely amorphous by x‐ray analysis. In this respect, PVF differs from poly(vinyl chloride) (PVC), where chlorination increases the softening point, and it resembles polyethylene where both crystallinity and softening point decrease with chlorination. 19F NMR analysis of the polymers indicates that up to a degree of chlorination of 1 chlorine atom per monomer unit, 50% of the substitution occurs on the α‐carbon of the PVF molecule. This result is very different from the predominant β‐chlorination of PVC reported by several workers. The chemical selectivity observed in the chlorination of PVF is in quantitative agreement with the results of free‐radical chlorination of organic compounds and can be rationalized by considering the size and the electronic properties of the fluorine atom. The results of 1H NMR analysis are also in support of a polymer structure where the chlorine atoms are distributed between α‐ and β‐carbons. Based on a comparison of the 19F and 1H NMR data, the average composition of chlorinated PVF at the 1 chlorine atom per monomer unit level can be represented as: C200H200F100Cl100 = (CH2)63(CHF)50(CHCl)24(CClF)50‐(CCl2)13.
Radiation‐induced crosslinking of cellulose with acrolein
Authors: Ishanov M. M. , Azizov U. A. , Nigmankhodzhayeva M. S. , Usmanov Kh. U. 
Published: April 2003

AbstractThe process of radiation‐induced crosslinking of cellulose is found to be highly influenced by radiation dosage and dose as well as by the solvents used and their concentration. The best crease resistance has been obtained in cases when cellulose is crosslinked with acrolein in the vapor phase. Moreover, the process is entirely radiation‐induced and practically no homopolymer is formed. Chemical analysis and investigations of infrared spectra indicate that crosslinking proceeds on vinyl as well as on aldehyde groups of acrolein.
Anionic graft polymerization of propylene sulfide on cellulose. II. Absorption of iodine, silver, and mercury on the graft polymers
Authors: Cohen Eliahu , Avny Yair , Zilkha Albert 
Published: April 2003

AbstractThe adsorption of iodine, silver nitrate, and mercuric chloride by cellulosic membranes grafted with polypropylene sulfide was investigated. It was found that the grafted polypropylene sulfide adsorbed iodine by complexation from aqueous solution or from gaseous phase. Adsorption from water led to the formation of a complex with molar ratio of I2 to propylene sulfide units of 1, and that while the complex formed from gaseous iodine had a molar ratio I2 to propylene sulfide approaching 2. Most of the sulfide groups participated in complexation. It was found that the complexation of the polysulfide was accompanied by degradation which was attributed to halogenation of the polysulfide at the tertiary carbon atoms. The iodine complex was more stable in water than in organic solvents, where most of the iodine was desorbed. The graft polymers adsorbed also by complexation silver nitrate and mercuric chloride. Adsorption could be described by a Freundlich type isotherm. At low concentrations most of the silver nitrate present in solution was adsorbed.
Free‐radical polymerizations initiated by triethylaluminum–cuprous chloride mixtures
Authors: Kawai Wasaburo , Ogawa Masaji , Ichihashi Taichi 
Published: April 2003

AbstractMethyl methacrylate was polymerized by triethylaluminum—cuprous chloride catalyst. A study of the polymerization kinetics indicated that the overall rate was represented by the equation, Rp = K[AlEt3] [CuCl]½ [M]2. The overall activation energy was 16.5 kcal/mole. From ESR measurement and the results of copolymerization of methyl methacrylate with styrene, it was suggested that the catalytic system has the character of a radical initiator. A polymerization scheme was also proposed.
Novel synthesis of photocrosslinkable polymers
Authors: Kato Masao , Ichijo Taro , Ishii Keizo , Hasegawa Masaki 
Published: April 2003

AbstractA new preparative route to photocrosslinkable polymers in which the polymers are produced directly from the polymerization of vinyl monomers having photocrosslinkable groups has been investigated. The photosensitive resins thus produced have higher sensitivity and resolution than conventional photosensitive resins. The monomers were synthesized from the esterification of vinylphenols or vinyl β‐chloroethyl ether with cinnamic acid, β‐styrylacrylic acid, and their homologs, and from the etherification of vinyl β‐chloroethyl ether with hydroxychalcones. Homopolymerizations of these monomers and their copolymerizations with other comonomers were investigated with the use of both radical and ionic initiators. It is shown that radical polymerization of the monomers gave soluble polymers only at low conversion. Anionic initiators did not initiate polymerization. Cationic polymerization imparted soluble polymers in high yield, except for the monomers bearing cyano groups, which generally gave insoluble polymers. Infrared and NMR spectroscopic investigation of the cationically obtained soluble polymers and comparative investigation by cationic polymerization of model compounds indicated that polymerization of the monomers proceeds through the vinyl double bond without affecting the photosensitive unsaturated bond. Thus, linear photocrosslinkable polymers with an intact photoreactive group may be produced by cationic polymerization. In general, these polymers have uniform structure and modifiable physical properties depending on the monomer used. The polymer thus obtained from β‐vinyloxyethyl cinnamate has been shown to have excellent properties for use as a photo‐resist.
Synthesis and thermal degradation of some ferrocene‐containing polyazines and poly‐schiff bases
Authors: Gamper R. G. , Funke P. T. , Volpe A. A. 
Published: April 2003

AbstractA series of ferrocene‐containing polymeric azines and polymeric Schiff bases have been synthesized by means of acid‐catalyzed solution polycondensations. The molecular structures of the polymers synthesized have been determined, and information concerning their thermal behavior has been obtained. Comparative thermal stabilities of the products of polymerization of aliphatic and aromatic diamines with 1,1′‐diformylferrocene and 1,1′‐diacetylferrocene were investigated by thermogravimetric analysis both in air and in an inert atmosphere. In the inert atmosphere, initial weight loss due to thermal stress did not occur below 300°C in all cases, and in many cases 50–70% residue of polymer sample remained at 700°C. The use of a fluorinated diamine led to the synthesis of a polymer which did not exhibit any significant enhancement of thermal properties. Investigation of the polymer products by direct inlet mass spectroscopy led to the observation that several of the systems contained significant amounts of cyclic dimers, although linear polymers were the major products in most cases. Extraction of the cyclic dimers followed by molecular weight determination by vapor phase osmometry confirmed their molecular structures.
Relative reactivities of some dienes and acetylenes in copolymerization with sulfur dioxide
Authors: Ivin K. J. , Walker N. A. 
Published: April 2003

AbstractThe reactivities of isoprene, piperylene,2,3‐dimethylbutadiene, hex‐1‐yne, and phenylacetylene, at −20°C, relative to that of cyclohexene, have been determined for the radical‐initiated copolymerization with sulfur dioxide to form 1:1 polysulfones. The unsaturated hydrocarbons were copolymerized with sulfur dioxide in pairs and the composition of the terpolymers determined from the 100 MHz NMR spectra. The dienes react 11–15 times as fast as hex‐1‐ene, while hex‐1‐yne reacts 16 times more slowly. Phenylacetylene reacts 21 times as fast as hex‐1‐yne. The relative reactivities are interpreted mainly in terms of the effect of electron delocalization on the stability of the product radical.
Studies with inorganic precipitate membranes. IV. Evaluation of apparent fixed charge on membranes
Authors: Siddiqi Fasih A. , Lakshminarayanaiah N. , Beg Mohammad N. 
Published: April 2003

AbstractMembrane potentials arising across four parchment‐supported ferrocyanide membranes of manganese, cobalt, silver, and cadmium when they separate 1:1 electrolyte solutions of concentration C1 and C2 such that C1 = 10C2, have been measured. The data have been used according to the procedure prescribed by one of the theories of membrane potential due to Teorell and Meyers and Sievers to derive values for the quantity of charge present on the membranes. An alternative procedure employed by Altug and Hair has been considered and found to overestimate the value for the charge on the membranes.
Chain folding in poly‐trans‐1,4‐butadiene crystals grown from various solvents
Authors: Stellman J. M. , Woodward A. E. 
Published: April 2003

AbstractCrystals of poly‐trans‐1,4‐butadiene of uniform size have been grown from three solvents (n‐heptane, methyl isobutyl ketone, and toluene) by using a minimum dissolution temeprature technique. The percentage of double bonds available for reaction in the crystals was determined by epoxidation in suspension; crystal thicknesses were measured by electron microscopy. These values were used to calculate the number of monomer units per fold. The number of available double bonds was found to increase with decreasing molecular weight, evidence for the presence of non‐reentrant chains (cilia) at the crystal surfaces. The nature of the chain fold in poly‐trans‐1,4‐butadiene crystals is discussed.
Scattering of light by deformed three‐dimensional spherulites
Authors: Van Aartsen J. J. , Stein R. S. 
Published: April 2003

AbstractA theoretical calculation of the Hv light‐scattering patterns for deformed three‐dimensional spherulites is presented. Affine deformation is assumed. The optic axis of the scattering element is allowed to lie at an arbitrary angle ß to the radius which is permitted to change in the course of the deformation in a manner that may depend upon the angular location in the spherulite. The consequences of twisting of the optic axis about the spherulite radius are also explored.