bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polycondensation of pyridine‐2,6‐dicarboxylic acid with some di‐ and tetraamino compounds
Authors: Banihashemi A. , Eghbali M. 
Published: April 2003

AbstractPyridine‐2,6‐dicarboxylic acid phenyl ester was condensed with 3,3′‐diaminobenzidine and 3,3′,4,4′‐tetraaminodiphenyl ether. Polyamides were also synthesized by condensation of the above ester with p‐phenylenediamine, benzidine, 4,4′‐diaminodiphenyl sulfide and 4,4′‐diaminodiphenyl sulfone. These amides had higher inherent viscosities and greater thermal stability than was reported before. Model compounds of imidazoles were prepared by condensation of the same ester with o‐phenylenediamine and 2,3‐diaminopyridine and of polyamides by condensation with aniline and 2‐aminopyridine. In the case of the polyimidazole, the completely closed ring of imidazole did not form. The ultraviolet spectra of model compounds were compared with those of the polymers. The thermogravimetric curves show that the polymers are stable up to more than 400°C under argon atmosphere. All polymers were insoluble in most organic and inorganic solvents. They dissolved only partially in DMSO and DMF. Inherent viscosity was measured for the soluble polymer fraction.
Polymerization of allyl phenyl ether
Authors: Hui K. M. , Yip L. C. 
Published: April 2003

AbstractAllyl phenyl ether polymerized rapidly and quantitatively to a resin with a structure similar to a phenolic thermoset in the presence of boron trifluoride etherate at 50°C. The structure and properties of this polyphenol were studied. A reaction mechanism involving rearrangement was discussed.
Linear polybenzyls. II. Lack of structure control in benzyl chloride polymerization
Authors: Kuo Jeffrey , Lenz Robert W. 
Published: April 2003

AbstractPolybenzyls were prepared from benzyl chloride with different catalysts and solvents and at different temperatures. A model compound reaction for the polymerization was studied by reacting benzyl chloride with an excess amount of diphenylmethane to determine the effect of reaction conditions on substitution distribution. The degree of branching of polybenzyl samples was characterized from the infrared absorption spectra by using peaks assigned to para and ortho disubstitution products and monosubstitution units. The degree of branching so obtained correlated well with the results from the model compound reactions and with the thermal stabilities of the polymers. Anthracene unit formation was also related to the isomer content, and addition of complexing agents such as SO2 or tetranitromethane caused a reduction in branching during polymerization. An unusual glass transition behavior was observed in these polymers.
Transition metal complexes of poly(vinylpyridines)
Authors: Agnew N. H. 
Published: April 2003

AbstractThe structures of the precipitates of free‐radical poly(4‐vinylpyridine) (Vpy), free‐radical poly(2‐Vpy) and isotactic poly(2‐Vpy) with M(II)Cl2 (M = Co, Ni, Cu, Zn) obtained from solution have been investigated. The polymer compounds are similar to the known crystalline monomeric Vpy complexes and, with one exception, are crosslinked by the metal dichloride. Co(II) and Zn(II) are tetrahedrally coordinated by the polymer, while the Ni(II) and Cu(II) complexes are probably tetrahedral and square‐planar, respectively. Because of the constraints of the polymeric ligands the stoichiometries of the complexes are not exactly the same as those of the monomeric Vpy complexes and from one to two Vpy units per metal halide are on average not coordinated. Atactic and isotactic poly(2‐Vpy) showed marked differences with regard to coordination of Ni(II). The questions of stereochemistry of the coordinated metal ion, stoichiometry of the complexes, intermolecular versus intramolecular complexation of the polymer chain, and the influence of polymer tacticity on the crystallizability of polymer complexes are discussed.
Use of model compounds to determine equilibrium melting points of polymers
Authors: Hay James N. 
Published: April 2003

AbstractEvidence is given for the relationship

describing the approximate dependence of the observed melting points Tm of oligomers on their degree of polymerization n, and its use in determining the equilibrium melting point T°m of the extended chain crystal and the heat of fusion Δh. Polyethylene and the n‐alkanes, poly(ethylene oxide) and poly(methylene oxide), polyphenylene and other systems are considered.
Relaxation processes in mixtures of polymers with linear amides
Authors: Kotlík P. , Heidingsfeld V. , Zelinger J. , Červinka O. 
Published: April 2003

AbstractResults of dynamic measurements of mixtures of polymer with linear low molecular amides are presented. New secondary relaxation processes that were revealed were elucidated by conformation motions of the amide group of low molecular compounds. The effect of water and similar substances on the character of low‐temperature relaxation processes is also discussed.
Grafting of styrene onto low molecular weight polymers and copolymers of butadiene
Authors: Gasperowicz Aleksandra , Łaskawski Włodzimierz 
Published: April 2003

AbstractThe grafting of styrene onto low molecular weight polybutadienes and butadiene–styrene co‐polymers was studied. A mathematical method was used for the design of experiments and for the determination of the optimum grafting conditions with respect to the conversion of styrene and the efficiency of grafting. The reaction parameters were temperature (65–105°C), time (2–10 hr), concentration of the initiator, polymer to monomer ratio (10/90–90/10) and dilution by solvent (toluene). The optimum grafting conditions were chosen under which 50–60 wt‐% of styrene was grafted onto backbone polymer at a high conversion of the monomer. It was found that the reactions producing graft copolymer prevailed over the styrene homopolymerization when the temperatures employed were lower (65–85°C), and the reaction time (8–10 hr), backbone polymer/monomer ratio, and the dilution by solvent were higher. The efficiency, density, and degree of grafting were found to increase with the increase in the molecular weight of the backbone polymer. The efficiencies and densities of grafting onto low molecular weight polybutedienes were higher than those of grafting onto low molecular weight butadiene–styrene copolymers. Grafting efficiencies and grafting densities were in the ranges 37.8–61.6 wt % and 0.06–0.26, respectively, in the studied range of number‐average molecular weights (M̄n = 2400–6000).
Kinetic approach to radiation‐induced grafting in the polyethylene–styrene system. II
Authors: Imai Masahiko 
Published: April 2003

AbstractThe investigation method reported in the previous paper was applied to four reaction methods: preirradiation method with reaction in liquid monomer, preirradiation method with reaction in monomer vapor, simultaneous irradiation method in liquid, and simultaneous irradiation method in vapor. The increasing patterns and values of the degree of grafting experimentally obtained roughly agreed with those calculated by using the same rate constants. At high monomer concentration, the rate of grafting was small; at low monomer concentration, the rate of grafting was large. Strictly speaking, the data by simultaneous irradiation method were somewhat larger than those by calculation. Two additional factors, as homopolymerization and the grafting from the radicals formed on the grafted polystyrene, were considered and discussed. The rate constants obtained were also discussed.
Thiourea–potassium bromate redox system‐initiated graft polymerization of methyl methacrylate and methacrylic acid on nylon 6
Authors: Hebeish A. , El‐Rafie M. H. , Waly A. I. 
Published: April 2003

AbstractThe ability of thiourea–potassium bromate redox system to initiate graft polymerization of methyl methacrylate (MMA) and methacrylic acid (MAA) onto nylon 6 was investigated under a variety of conditions. With both monomers, increasing potassium bromate concentration up to 20 mmole/l. caused a significant enhancement in the graft yield. Above this concentration, the latter nearly leveled off in the case of MAA and decreased in the case of MMA. The effect of increasing thiourea concentration up to 15 mmole/l. was to bring about an outstanding increase in the graft yield. Above this concentration grafting decreased sharply. The grafting yield increased as the reaction time increased, then leveled off. The rate of reaction is temperature‐dependent. Within the range studied, the rate of grafting follows the order 70 > 60 > 50°C. Nylon samples grafted with MAA showed higher moisture regain than the ungrafted nylon. The increment in moisture regain depends on the percent graft yield.
Thermal degradation of poly(bismaleimides)
Authors: Stenzenberger H. D. , Heinen K. U. , Hummel D. O. 
Published: April 2003

AbstractThermal decomposition of poly(bismaleimides) has been investigated by using programmed and isothermal thermogravimetric analysis (TGA) in nitrogen. Reaction rates and overall activation energies were calculated from isothermal weight less studies. For five aliphatic poly(bismaleimides) a linear correlation between the activation energies and the number of methylene groups in the sequence between the maleimide residues was found. Aliphatic poly(bismaleimides) follow first‐order kinetic law up to a conversion of 60‐70% having activation energies between 196 and 256 kj/mole. poly(2,4‐bismaleimidotoluene) which was found to have in highest polymer decomposition temperature (PDT) did follow the first‐order kinetics up to a conversion of 60% in contrast to other aromatic poly(bismaleimides). In addition to the TGA, the pyro‐field ion mass spectra of the polymers were recorded and are discussed.
Polymerization of 5‐(1‐adamantyloxy)‐2H‐pyrrole‐2‐one
Authors: Wilson John C. 
Published: April 2003

Abstract5‐(1‐Adamantyloxy)‐2H‐pyrrole‐2 one has been homopolymerized and copolymerized with a variety of comonomers. Polymerization was conducted in chloroform solutions with α,α′‐azobisisobutyronitrile initiator. Evidence of polymerization was achieved through infrared and NMR spectra and elemental analysis. Moderate molecular weights were achieved as determined by inherent viscosity measurements and gel‐permeation chromatography. Photolysis of the polymers with ultraviolet radiation induces a photochemical rearrangement resulting in the formation of isocyanate functions. A proposed mechanism suggests α‐cleavage of the carbonyl to give a 1,5‐diradical which rearranges to a 1,3‐diradical with subsequent ring closure to give a polymer with cyclopropyl isocyanate moieties in the backbone. DSC data show all polymers to display intense exothermic activity at temperatures near 200°C on initial heating and glass transition temperatures between 194 and 245.5°C on subsequent heating. Thermolysis of the homopolymer causes rearrangement to poly[N‐(1‐adamantyl) maleimide]. Reactivity ratios were determined for the systems styrene (M1) and 5‐(1‐adamantyloxy)‐2H‐pyrrole‐2‐one (M2) (r1 = 0.06, r2 = 0.07) and methyl methacrylate (M1) and 5‐(1‐adamantyloxy)‐2H‐pyrrole‐2‐one(M2) (r1 = 0.35, r2 = 0.70). Q and e values for 5‐(1‐adamantyloxy)‐2H‐pyrrole‐2‐one are 3.40 and 1.59, respectively.
Influence of rigid polymer matrices on the reversible photochemical reaction of α‐p‐dimethylaminophenyl‐N‐m‐nitrophenylnitrone
Authors: Smets G. J. , Matsumcto S. 
Published: April 2003

AbstractThe thermally reversible photocyclization of α‐p‐dimethylaminophenyl‐N‐m‐nitrophenylnitrone (I) to the corresponding oxaziridine (II) was studied in solution and in rigid polymer matrices. Irradiation with light of wavelength above 380 nm causes a clean transformation of (I) to (II) in solution as well as in polymer matrices. The quantum yield of the photoreaction in solution is about 0.06, the value being almost independent of the nature of the solvent and the irradiation time. In poly‐(methyl methacrylate) (PMMA) and in polystyrene (PSt) films, the photocyclization shows initial quantum yields of 0.1 and 0.23, respectively, which decrease with irradiation time. In solution in the dark, II reverted mainly to I with formation of side product(s) in a first‐order reaction. The recovery of I during the dark reaction (60–90%) as well as the rate constant of the reaction are strongly affected by the solvent. The kinetics of the thermal return in the two polymer matrices does not follow the first‐order rate law. The initial reaction rate as well as the extent of the recovery of I in PMMA film are greater than those in ethyl acetate.
Higher aliphatic polyaldehydes. IV. Transitions in poly(n‐valeraldehyde), poly(n‐hexaldehyde), poly(n‐heptaldehyde), and poly(n‐octaldehyde)
Authors: Negulescu I. , Vogl O. 
Published: April 2003

AbstractCrystalline polymers of n‐valeraldehyde, n‐hexaldehyde, n‐heptaldehyde, and n‐octaldehyde were prepared by anionic polymerization with lithium tertiary butoxide as the initiator at low temperatures. The polymers were end‐capped with acetic anhydride, and their thermal stability was studied primarily by DTG. It was found that all polymers degrade rapidly above 150°C. All polymers show a dual melting‐point behavior. The first melting region, which is associated with the melting of the side chain, is 80–85°C for poly(n‐valeraldehyde); 87–90°C for poly(n‐hexaldehyde); 78–101°C for poly(n‐heptaldehyde); and 41–69°C for poly(n‐octaldehyde). Annealing and quenching of the samples showed that this melting‐point region consisted of several endotherm peaks whose intensity changed according to the thermal history of the sample. Although the samples are apparently highly crystalline, the side‐chain crystallinity is apparently only in the 20% range.
Study of the direct detection of crosslinks in hydrocarbons by 13C‐NMR. I. Preparation and characterization of model compound 1,1,2,2‐tetra(tridecyl) ethane
Authors: Bennett R. L. , Keller A. , Stejny J. 
Published: April 2003

AbstractThe present series of papers is the commencement of a study aimed at the direct detection and quantification of crosslinking in hydrocarbons with the ultimate objective of a precise study of radiation‐induced crosslinking in polyethylene. The subject of the present paper is the synthesis of a model compound containing a crosslink in a well‐defined position sufficiently remote from the chain ends to be representative of an average crosslink in polyethylene. Such a compound in the form of 1,1,2,2‐tetra(tridecyl) ethane has been synthetized and isolated in pure form in the course of the present work. Melting points and x‐ray spacings of the new compound have been determined, and a comparison with the corresponding linear paraffins has been made. Effects are noted relating to the influence of molecular shape on the GPC elution volume, in which context an observation on a cyclic paraffin is also quoted.
Study of the direct detection of crosslinking in hydrocarbons by 13C‐NMR. II. Identification of crosslink in model compound and application to irradiated paraffins
Authors: Bennett R. L. , Keller A. , Stejny J. , Murray M. 
Published: April 2003

AbstractA 13C‐NMR investigation was carried out in aid of direct detection of crosslinks in hydrocarbons with the future objective of studying radiation‐induced crosslinking in polyethylene by a direct method. The resonance signal due to a tertiary carbon atom appropriate to a crosslink far remote from molecular ends has been identified in a definitive manner with the aid of the H‐shaped model compound 1,1,2,2‐tetra(tridecyl)ethane synthetized in Part I of this study. This identification was then put to use in the examination of the irradiated linear paraffins n‐hexadecane and n‐eicosane, where it enabled the detection of radiation‐induced crosslinks. This crosslinking could then be associated with corresponding changes in molecular weight (dimer, trimer formation) as revealed by discrete peaks in the gel‐permeation chromatograms of the same samples and randomness of the crosslinking process in the liquid state of these compounds being inferred.
Conformational freedom of polyamide chains above the melting point
Authors: Carfagna Cosimo , Vacatello Michele , Corradini Paolo 
Published: April 2003

AbstractThe melting behavior of diamides of general formula (n‐CpH2p+1)CONH(CH2)qNHCO(nCpH2p+1) has been investigated by differential scanning calorimetry (DSC). The close similarity of the melting behavior of these low molar mass compounds with that of polymeric amides is discussed in terms of restricted conformational disorder in the amorphous state, due to the high degree of retention of hydrogen bonding.
Copolyamides from adipic and truxillic acids: Synthesis and characterization by direct pyrolysis in the mass spectrometer
Authors: Caccamese S. , Foti S. , Maravigna P. , Montaudo G. , Recca A. , Luderwald I. , Przybylski M. 
Published: April 2003

AbstractThe synthesis of a series of polyamides and copolyamides containing α‐truxillic and adipic units in the chain is reported. The thermal degradation of these polymers was investigated by direct pyrolysis in the ion source of a mass spectrometer. Thermal degradation reactions were followed directly by this method by detecting the thermal‐ and electron‐impact‐induced fragments. The results obtained show a good correlation between the intensity of mass peaks characteristic of truxillic and adipic moieties and the composition of the copolyamides, as ascertained by elemental analysis. This is an important result since it shows the potential of the direct pyrolysis method in the analysis of copolymers. Relevant information on the relative thermal stabilities of the polymers investigated has been also obtained.
Grafting of acrylamide onto methyl cellulose by persulfate ion
Authors: Bardhan Krishna , Mukhopadhyay Sailes , Chatterjee Satya. R. 
Published: April 2003

AbstractAcrylamide was grafted onto methyl cellulose backbone by using potassium persulfate as initiator in aqueous solution, and variables affecting the copolymerization were studied. It was found that efficiency of grafting was maximum at an initiator concentration of 3.7 × 10−4 mole/l. Grafting was found to increase steadily with increase in monomer/polymer ratio and with temperature up to 40°C.
Radiation‐induced grafting of hexafluoroacetone to polyethylene
Authors: Clark Chester F. , Silverman Joseph 
Published: April 2003

AbstractAlthough hexafluoroacetone is not polymerized by ionizing radiation, it is shown that γ‐irradiation of hexafluoroacetone dissolved in polyethylene films produces a graft with a G value of 500 and, therefore, a kinetic chain length of 200. The effects of dose rate (0.021–3.55 Mrad/hr), temperature (21–53°C), and pressure (1.5–6.2 atm) on the graft rates have been measured. Also the effect of temperature (21–53°C) on the postirradiation grafting reaction and on the physical properties of the grafted films have been investigated. Together with solubility, diffusivity, infrared, and EPR data, the results lead to the following mechanism:

equation image

The first step represents production of secondary alkyl radicals in the polyethylene by irradiation of the polymer–monomer system. The second step involves the linkage of the monomer to the radical site to form the alkoxy radical. Since it cannot add to another monomer unit, this radical abstracts a hydrogen atom from an adjacent polyethylene chain in the third step. Radical R· can then continue the kinetic chain. Radical combination and radical–impurity reactions terminate the chain. The graft may be unique in that it is the only one we have found in which a pendant group containing only one monomer unit is attached by a chain reaction. At dose rates up to 0.215 Mrad/hr, the grafting was linear with time and proportional to the 0.73 power of the dose rate at 21°C and to the 0.81 power at 53°C. The reaction is insensitive to increases in dose rate above 0.215 Mrad/hr where diffusivity measurements show the reaction to be diffusion‐controlled. The rate of reaction increased 10% when the temperature was increased from 21 to 53°C. While there was significant postirradiation grafting reaction at 21°C, there was none at 53°C. The results do not fit the equations of reaction‐controlled steady‐state graft‐polymerization kinetics. The deviations arise from an observed increase in monomer solubility in the film with increasing graft combined with low diffusivity of the monomer in polyethylene, and the presence of a radical‐scavenging impurity which terminates the kinetic chain with the appearance of a relatively stable radical. EPR data suggests that the impurity is a trace of oxygen which may be produced radiolytically.
Studies on propagating species in cationic polymerization of styrene derivatives by acetyl perchlorate or iodine. III. Effect of salt on cationic copolymerization of styrene derivatives with vinyl ethers by acetyl perchlorate
Authors: Higashimura Toshinobu , Yamamoto Kenji 
Published: April 2003

AbstractA common‐ion salt, tetra‐n‐butylammonium perchlorate, was found to affect the monomer reactivity ratios in the cationic copolymerization by acetyl perchlorate of styrene with p‐methylstyrene and of 2‐chloroethyl vinyl ether with p‐methylstyrene, but not those for the copolymerization of 2‐chloroethyl vinyl ether with isobutyl vinyl ether. In the copolymerization of p‐methylstyrene with styrene or with 2‐chloroethyl vinyl ether, the addition of the common‐ion salt in a polar solvent shifted the monomer reactivity ratios to those in a less polar solvent. The molecular weight distribution analysis of the copolymer suggested that the addition of the common‐ion salt depresses the dissociation of propagating species. Therefore, it was concluded that a propagating species with a different degree of dissociation shows a different relative reactivity towards two monomers. The nature of propagating species was also discussed on the basis of the common‐ion effect on the monomer reactivity ratios in various solvents.
Regular copolyamides. I. A facile method for the preparation of diamine‐oxamides
Authors: Chang H. J. , Vogl O. 
Published: April 2003

Abstractα,ω‐Diamine‐oxamides with 2–12 CH2 groups between the two amino groups were obtained by the reaction of the diamines and diethyl or dimethyl oxalate. Diethyl oxalate is added slowly to a substantial excess of diamine in the proper solvent over a period of time under controlled temperature conditions. All variables are very important for each individual diamine in order to obtain optimal conversions to the diamine‐oxamides under the most favorable conditions. Diamine‐oxamides were obtained in approximately 80% yield with only small amounts (5–10%) of the corresponding polyoxamides as the side product. Diamine‐oxamides from diamines with less than six methylene groups are water‐soluble. All diamine‐oxamides show an alternation of their melting points and are useful intermediates for the preparation of regular copolyoxamides.