bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of photo‐ and radiation‐induced radical formation in polyethylene by ESR spectroscopy
Authors: Tsuji Kozo
Published: April 2003

The behaviors of free radicals produced in polyethylene irradiated with ultraviolet light and electron beams were compared in connection with primary processes of radical formation and trapping regions of free radicals. In the case of irradiation with ultraviolet light, an ESR spectrum observed at −196°C immediately after irradiation is an eight‐line spectrum due to alkyl radicals of the type CH2ĊHCH3, while in the case of ionizing radiation, a six‐line spectrum due to CH2ĊHCH2 was observed. The former radicals are produced by the Norrish type I reaction of the carbonyl groups contained in the polymer, followed by radical rearrangement; and the latter are formed by dissociation of hydrogen atom from the excited state of the polymer or ion‐molecular reactions. From the sensitivity to oxygen molecules, it was deduced that free radicals are trapped in amorphous regions after ultraviolet irradiation, but mainly in crystalline regions after irradiation with electron beams. Saturation studies of ESR spectra seem to support this conclusion.
Benzobistriazolophenanthroline polymers
Authors: Evers Robert C.
Published: April 2003

The polycondensation of aromatic dihydrazidines (bisamidrazones) with 1,4,5,8‐naphthalenetetracarboxylic acid or 1,4,5,8‐naphthalenetetracarboxylic dianhydride in polyphosphoric acid led to high yields of soluble benzobistriazolophenanthroline polymers. Inherent viscosities in methanesulfonic acid of 0.25–2.51 dl g were recorded. Prior to polymer synthesis, a series of model compounds were prepared by reactions analogous to the polycondensation reaction. The polymer structure was established by elemental analysis and spectral comparisons of the polymers with model compounds. The thermal properties of the polymers were studied by thermal gravimetric analysis, differential thermal analysis, differential scanning calorimetry, and softening under load. Onset of breakdown in an air atmosphere occurs in the 440–450°C range. No softening under load was observed up to 450°C.
Les anions‐radicaux de l'isoprène et du butadiène intermédiaires de synthèse en chimie organique
Authors: Brossas J. , Pinazzi C. P. , Clouet F.
Published: April 2003

We have synthesized a series of alkadiene and dialcohol homologs of terpenoid natural products by using anion‐radicals of isoprene and butadiene. The reactions of the two monomers were initiated anionically by use of alkali metal–aromatic hydrocarbon complexes. The polymerization was stopped at the dimer stage. This method constitutes a route of synthesis for numerous organic compounds, such as alcohols and hydrocarbons.
Caractère séquencé des polyacroléines préparées par voie anionique
Authors: Calvayrac Henri , Thivollet Pierre , Golé Jean
Published: April 2003

Several independent studies confirm that anionic polyacroleins are block polymers. Chemical analysis, thermogravimetric studies, and variations of the refractive index increment and sequences lengths all support this hypothesis.
Competition between thermal decomposition and hydrolysis of 2,2'‐azobis(2‐amidinopropane) in aqueous solution
Authors: Ito Katsukiyo
Published: April 2003

The thermal decomposition and hydrolysis of 2,2′‐azobis(2‐amidinopropane) were examined as functions of pH. The rate of decomposition decreased with increasing pH. The specific rates at 60°C were 3.85 × 10−5 1/sec at pH 0.90 and 2.5 × 10−5 1 see at pH ≥ 8.5. The hydrolysis in alkaline solution yielded 2,2′‐azobis(2‐carbamylpropane) which was stable to thermal decomposition. The relation between the specific rate of hydrolysis kh′ and the concentration of hydroxyl ion was obtained as kh′ = 4.0 × 10−2 [OH]0.50 1/sec at 60°C. In alkaline solution, the rate of hydrolysis was considerably larger than that of thermal decomposition. A mechanism for this hydrolysis is propesed.
Synthesis of photocrosslinkable polyesters by the Knoevenagel reaction
Authors: Ravve A. , Pasternack G. , Brown K. H. , Radlove S. B.
Published: April 2003

A new group of photocrosslinkable polyesters formed by the Knoevenagel reaction is described. The approach permits preparation of photoesensitive polymers, where physical properties can be potentially varied through choice of the polyol and the dicarboxylic acid. The following compounds were prepared and studied: (1) products from a Knoevenagel reaction of poly(trimethylopropane azelate cyanoacetate) with benzaldehyde, furaldehyde, and 2‐ethylbutyraldehyde and (2) products from a Knoevenagel reaction of poly(1,3‐propyl malonate) with benzaldehyde, p‐methoxybenzaldehyde, and 2‐ethylbutyraldehyde. Conventional unsaturated polyesters such as poly(1,3‐propyl fumarate) and poly(1,3‐propyl maleate) were prepared and used for comparison.
Polymerization of 1,2‐butylene oxide initiated by triphenylmethyl salts. I. Kinetics with 1,2‐dichloroethane as solvent
Authors: Hornof V. , Gabra G. , Blanchard L. P.
Published: April 2003

1,2‐Butylene oxide was polymerized in 1,2‐dichloroethane in the temperature range −20 to + 10°C. Triphenylmethyl salts of hexafluoroantimonate (Ph3CSbF6), hexafluoroarsenate (Ph3CAsF6), and hexafluorophosphate (Ph3CPF6) were employed as initiators. The reactions are characterized by a fast initiation process accompanied by rapid consumption of monomer. This initial stage is followed by a relatively slower polymerization during which the rate of monomer consumption is first‐order in respect to monomer. Variation of the counteranion produces very little influence on the rate. The difference between the thermodynamic parameters found for the first and second stages of the reaction are explained on the basis of two different polymerization mechanisms. The linear dependence of rate on initiator concentration indicates that propagation takes place by ion‐pairs only within the range investigated here.
Polymérization anionique de l'isoprène par les insertions ternaires graphite–métal alcalin–solvant
Authors: Essel Alain , Pham Quang Tho , Golé Jean
Published: April 2003

The examination by HR–NMR of the microstructure of polyisoprenes synthesized in the presence of alkali metal–graphite compounds reveals that the polymerization has an anionic character. The microstructure of the polymers depends on the nature of the active centers, which depends on the solvent used in the preparation of the graphite compounds or as polymerization medium. With powdered alkali metal–graphite compounds, the propagation does not differ from the anionic one occurring in a homogeneous medium. Except for K–graphite, an enhancement of the 1–4 addition mode is observed if grains of Li or Na–graphite are used in mass polymerization. This change in the microstructure could be explained by the competition between the rate of propagation and the rate of diffusion of the growing chains from the grains to the homogeneous phase of the polymerization medium.
Energy transfer processes involving ultraviolet stabilizers. Quenching of singlet oxygen
Authors: Guillory J. P. , Cook C. F.
Published: April 2003

The role of electronically excited singlet (1Δg) oxygen molecules in the photooxidation of polymers has received increased attention in recent years. Little information regarding the interaction of ultraviolet stabilizers with singlet oxygen is known, however. In this study, singlet oxygen was produced by a microwave discharge in a flow system and rate constants were obtained for quenching by ultraviolet stabilizers. It was found that some nickel chelate stabilizers are effective quenchers of singlet oxygen and their quenching behaviors can be correlated with ultraviolet stabilization effectiveness in thin polypropylene and polyethylene films. The best oxygen quenchers of those examined are nickel chelates with sulfur donor ligands.
Reversible crosslinking in cellulose. VII. Memory effect of the crosslinking medium in the dyeing of crosslinked cotton
Authors: Sakamoto Munenori , Yamada Yoshio , Tonami Hiroaki
Published: April 2003

Cellulose β‐mercaptoethylaminocarboxylate made from unmercerized cotton was partially oxidized in various solvents of different swelling power followed by treatment with excess methyl iodide to yield partially disulfide‐crosslinked cotton samples of about the same degrees of crosslinking containing sulfonium groups of about the same contents. The effect of the solvent in crosslinking on the equilibrium and kinetics of dyeing with three dyes (Orange II, Direct Scarlet B, and Direct Sky Blue A) of different molecular size was investigated. The 1:1 ionic bonding was observed at equilibrium between sulfonic acid groups in dye molecules and sulfonium groups in modified cottons in cases of Orange II and Direct Scarlet B. The equilibrium uptake of the largest dye, Direct Sky Blue A, was much influenced by the solvent used in crosslinking; the higher the degree of swelling in crosslinking, the larger the equilibrium uptake. The diffusion rate of Direct Scarlet B was much affected by the solvent used; the higher the degree of swelling, the higher the diffusion rate. The pore structure of the crosslinked cotton was discussed. The crosslinked cotton seemed to have a “memory” of the state at the time of crosslinking and to have a tendency to come back close to that state when placed in a dye bath.
Photopolymerization of methyl methacrylate with the use of bromine as photoinitiator
Authors: Ghosh Premamoy , Mitra Partha Sarathi , Banerjee Amar Nath
Published: April 2003

Low concentrations of bromine (0.008–0.06M) were used to initiate photopolymerization of MMA in bulk and in diluted (near bulk) systems, the diluents or solvents used being benzene, toluene, dioxane, tetrahydrofuran, carbon tetrachloride, chloroform, methylene chloride, and methanol. Polymerization in bulk follows usual free‐radical kinetics. Inert solvents (benzene, toluene) as well as the other solvents used enhance the rate of polymerization MMA even when used in the range of catalytic concentrations (0.04–0.4M). An initiation mechanism involving solvent molecules appears to be predominant in diluted systems.
Poly α‐ester degradation studies. V. Thermal degradation of polyglycollide
Authors: Cooper D. R. , Sutton G. J. , Tighe B. J.
Published: April 2003

The thermal degradation of polyglycollide [poly(methylene carboxylate)] has been studied over the temperature range 250–400°C by using the combined kinetic and analytical technique previously described. The results obtained from thermogravimetry and product analysis were in many ways similar to those from previous work involving higher poly‐α‐esters. Thus the reaction was predominantly first‐order and the major degradation product was glycollide monomer. This confirms the observations of Carothers and is best interpreted in terms of an intramolecular ester interchange process. Kinetic studies have shown that the first‐order rate constant k is related to temperature T by the expression:

The results from gas evolution analysis showed consistent and marked deviation from first‐order behavior. This is interpreted in terms of the greater sensitivity of this technique to traces of acidic degradation products. Solution viscometry was used to demonstrate the effect of degradation conditions on molecular weight change in both thermogravimetric and gas evolution techniques.
Sulfur‐containing polymers. X. Aromatic poly(sulfenyl thiocarbonates)
Authors: Kobayashi Norio , Osawa Akiko , Fujisawa Tamotsu
Published: April 2003

Aromatic poly(sulfenyl thiocarbonates) have been synthesized by the interfacial polycondensation of bis(dithiocarbonyl chlorides) with bisphenols. Bisphenols having the hydroxyl groups on separate rings gave polymers in high yields. The inherent viscosities of the polymers ranged from 0.22 to 0.51. In general, they were soluble in chloroform, sym‐tetrachloroethane, hexamethylphosphoramide, m‐cresol, and dimethylformamide and formed transparent tough films on evaporation of chloroform solutions. Almost all of the polymers were amorphous and gave melt‐spun fibers. The polymer films decomposed upon ultraviolet irradiation with liberation of carbonyl sulfide.
Thermomechanical behavior of a polyphenylquinoxaline
Authors: Augl Joseph M. , Booth Hubert J.
Published: April 2003

Crosslinking of linear poly[2,2′‐(1,4‐phenylene)‐6,6′‐bis(3‐phenylquinoxaline)] (PPQ) by isothermal heat exposure in the temperature range between 425 and 490°C was investigated by means of torsional braid analysis. The change in glass transition temperature due to isothermal exposure was used as a kinetic parameter. In order to determine the effect of molecular weight and type of polymer chain ends, three PPQ samples were prepared that differed only in molecular weight and polymer chain endgroups. The apparent activation energy of isothermal crosslinking was independent of molecular weight and chain endings. Its value of 60 kcal/mole is the same as that for the thermal degradation of PPQ (determined by isothermal weight loss measurements). The rates of change of Tg at a particular temperature, however, are a function of both molecular weight (at least for these polymers that do not have a sufficiently high molecular weight) and the type of polymer chain ends. It was observed that isothermally crosslinked PPQ gave a higher break point in the TGA curve and also an increased char yield at 800°C than the linear precursor.
Some problems of nonequilibrium copolycondensation
Authors: Korshak V. V. , Vinogradova S. V. , Vasnev V. A. , Perfilov Yu. I. , Okulevich P. O.
Published: April 2003

The influence of the reactivity of the starting compounds and reaction conditions on the formation of the macromolecules of copolymers has been investigated for a nonequilibrium copolycondensation in solution by acceptor‐catalytic polyesterification. In the nonequilibrium copolycondensation in solution, copolymers with different distributions of units may be formed, depending on various factors. Introduction of all amounts of acid chloride (intermonomer) in the beginning of the nonequilibrium copolycondensation leads to the formation of copolymers with statistical distribution of the units independent of the difference in reactivity of the comonomers used. For synthesis of copolymers with a block structure by one‐stage nonequilibrium polycondensation in solution the initial comonomers must have different reactivities (r ≠ 1) and the rate of intermonomer introduction must be lower than that of its reaction with the more reactive comonomer. On varying the above factors, block copolymers with different lengths of block segments may be obtained.
Radiation‐induced polymerization of cyclohexene sulfide in the solid state
Authors: Hiramoto Tetsuo , Nishii Masanobu , Fiala Vladimir , Yamaoka Hitoshi
Published: April 2003

Radiation‐induced solid‐state polymerization of cyclohexene sulfide has been investigated. Differential thermal analysis shows that this compound has a phase transition point at −74°C and behaves as a plastic crystal in the temperature range from −74 to −20°C (melting point). By rapid cooling, this plastic crystal was easily supercooled, and below −166°C a glassy crystal, i.e., a supercooled nonequilibrium state of plastic crystal, was obtained. In‐source polymerization proceeded in the plastic crystalline state. Postpolymerization of glassy crystalline monomer irradiated at −196°C occurred above −166°C (glass transition point) during subsequent heating.
Adsorption of polymers at the solution–solid interface. IX. Solution adsorption of nitrile rubbers on silicas
Authors: Clark P. J. , Howard G. J.
Published: April 2003

The adsorption of three acrylonitrile–butadiene random copolymers from two solvents has been studied: two pyrogenic silicas of differing surface areas, which had received several surface modifications, were used as adsorbents. Infrared spectroscopic studies confirm that the nitrile groups bond to the silica surface. The amount of copolymer adsorbed is related to the acrylonitrile content, which also controls the copolymer solubility: adsorptions are higher from benzene than from a better solvent, trichloroethylene. Vapor sorption of model compounds indicate how the adsorbent surface area and surface composition affect monolayer capacities: heats of adsorption are not markedly altered by the adsorbent modifications.
Poly‐α‐ester degradation studies. III. Effect of β‐chlorination on polymer degradation
Authors: Patterson A. , Sutton G. J. , Tighe B. J.
Published: April 2003

The thermal degradation of two β‐chlorinated versions of poly(isopropylidene carboxylate) has been studied by the combined thermogravimetric and gas evolution techniques described previously. Poly(3‐chloro‐2‐methyl‐2‐hydroxypropionic acid) was found to decompose by a predominantly first‐order process which was characterized by kinetic parameters similar to those obtained for poly(isopropylidene carboxylate). These are interpreted in terms of an intramolecular ester‐exchange process. As the reaction proceeds intermolecular elimination of hydrogen chloride leads to crosslinking and ultimately to the formation of a carbonaceous char. This process is much more marked in the randomly β‐chlorinated analog of poly(isopropylidene carboxylate). With this polymer, drastic deviation from first‐order behavior is observed in thermogravimetric results, even in the early stages of reaction. Gas evolution analysis, being more influenced by degradation fragments having an appreciable vapor pressure, yields reasonable first‐order data and indicates that the intramolecular interchange mechanism is still an important process. In general, the introduction of β‐chlorine atoms is seen to reduce the rate of thermal decomposition of poly‐α‐esters.
Poly(diphenylsiloxy)arylazines. I. Synthesis and characterization
Authors: Goldsberry R. E. , Adamson M. J. , Reinisch R. F.
Published: April 2003

The synthesis of poly(diphenylsiloxy)arylazines and the preparation of the necessary aromatic aldehyde and azine precursors are described. This new family of polymers was prepared by a modified melt‐condensation reaction of hydroxyl‐substituted phenyl‐and naphthylazines with bis(anilino)diphenylsilane. The resulting polymers have been characterized by elemental analysis, gel‐permeation chromatography, vapor‐phase osmometry, and absorption spectroscopy. Assignment of a polymer backbone composed of alternating diphenylsiloxane and arylazine moieties was made on the basis of the infrared absorption bands and by comparison of the fluorescence and absorption spectra of the polymers with those of model compounds. The molecular weight of the polymers was found to depend on temperature, reaction time, and the ratio of monomers. The formation of low molecular weight products was avoided by maintaining reaction temperatures below the decomposition point of the arylazine and by keeping the ratio of silylamine to arylazine at about 3:1. Molecular weights as high as 38,000 and extents of conversion of 85% were obtained by the described melt condensation procedure. The molecular weight of another member of the family was increased from 4600 to 8100 by a post‐polymerization scheme, involving the reaction of aromatic hydroxyl and anilinosilane endgroups. Significant crosslinking via ortho hydroxyl groups during the polymerization of tetrahydroxyarylazines can be ruled out because of the solubility of the polymers in chloroform or tetrahydrofuran and on the basis of their fluorescence spectrum.
Mechanism of thermal decolorization of benzospirans in some amorphous polymeric matrices
Authors: Kryszewski M. , Łapienis D. , Nadolski B.
Published: April 2003

The photochromic effect has been investigated for three compounds of the benzospiran group dissolved in amorphous polymers: poly(methyl methacrylate), poly(n‐butyl methacrylate), poly(vinyl acetate), and poly(vinyl n‐butyrate). The kinetics of the thermal bleaching reaction above Tg of the matrix follow a first‐order equation due to the averaging of free volume distribution related to the diffusion of segments in viscoelastic state. A more complex mechanism of decolorization below Tg has been considered from the point of view of unequal, discrete distribution of environments in which the photochromic molecules exist in the glassy matrix. A change of the activation energy and the mechanism of color decay on passing through Tg is not a rule (PVB), which shows, that for a polymer having long, flexible chains, secondary glass transition phenomena play a decisive role. In the case of glassy polymers (PMMA), the photochromic effect of benzospirans may be employed to determine Tβ. It seems, that in addition to steric restrictions for trans–cis isomerization in the decolorization process one must consider the interactions of photochromic molecules with the matrix as well as their chemical nature.
Mechanism of alternating copolymerization of polar and hydrocarbon polymers
Authors: Golubev V. B. , Zubov V. P. , Georgiev G. S. , Stoyachenko I. L. , Kabanov V. A.
Published: April 2003

Radical copolymerization of butyl methacrylate with 2,3‐dimethylbutadiene in the presence of Al(C2H5)2Cl or ZnCl2 results in alternating copolymers. The nature of active centers and the mechanism of polymerization in these systems have been studied by means of ESR measurements in combination with calorimetry at low temperatures. The active centers are monoradicals propagating by alternative addition of single monomer molecules; thus the reaction can be described in terms of a conventional kinetic scheme of radical additional polymerization. Participation of binary donor—acceptor complexes of the monomers in the reaction has not been confirmed. Similar conclusions have been drawn for the other alternating system studied, maleic anhydride–2,3‐dimethylbutadiene. The feasibility of formation of alternating copolymers in the studied systems by the conventional mechanism of binary radical copolymerization has been confirmed by qualitative quantum‐chemical treatment of the propagation reactions with due account to the donor–acceptor interactions in the transition state.
Polymerization of isoprene initiated by the reaction products of zirconium allylic complexes and titanium chlorides
Authors: Kormer V. A. , Vasiliev V. A. , Kalinicheva N. A. , Belgorodskaya O. I.
Published: April 2003

Reaction of (all)4Zr with TiCl4 involves the migration of the allyl ligands to titanium which is accompanied by the reduction of titanium to a tri‐ and divalent state and the formation of diallyl. The reaction products are found to initiate polymerization and oligomerization of isoprene. The course of the isoprene reactions and the properties of the resulting polymers are determined by the nature of the complexes formed. The reaction products of TiCl4 or TiCl3 with (all)2ZrCl2 initiate cationic polymerization of isoprene. Complexes resulting from the reaction of TiCl3 with (all)4Zr or (all)3ZrCl lead to cis‐1,4‐polyisoprene.
Regularities of diene copolymerization by coordination catalytic systems and the mechanism of stereoregulation
Authors: Dolgoplosk B. A. , Beilin S. I. , Korshak Yu. V. , Makovetsky K. L. , Tinyakova E. I.
Published: April 2003

A study has been conducted of the relative reactivity of a series of dienes (butadiene, isoprene, 2,3‐dimethylbutadiene, cyclohexadiene‐1,3), as well as of butadiene and styrene, in copolymerization by various coordination catalyst systems based on transition metals: nickel, cobalt, titanium, chromium, molybdenum, and tungsten. The microstructure of homopolymers and copolymers of dienes has been investigated. Regularities have been established in the mutual influence of the comonomers on the microstructure of a polymer chain. Experimental data on the influence of the concentration of diene monomer, and electron‐donating and electron‐accepting compounds on the microstructure of polydiene chain have been used in discussing the alternative mechanisms of stereoregulation in diene polymerization by active centers of the π‐allyl type.
Viscosity study of radiation chemistry of polystyrene
Authors: Chau T. C. , Rudin Alfred
Published: April 2003

The effects of γ‐radiation on aqueous polystyrene emulsions were followed by measurements by intrinsic viscosities of soluble polymer in toluene. Estimates of incipient gel dose from intrinsic viscosity data do not coincide closely with those from measurements of gel content. This uncertainty and those in molecular weight averages make it difficult to assign a precise value to G(crosslink), even when the scission crosslinking ratio in the particular system is reliably known. The intrinsic viscosity of sol polymer in the postgel region decreases with increasing dose to an asymptotic value. The decrease is as expected if larger molecules are progressively linked into the gel network and the asymptote may be attributable to cyclization. Present theories of branching do not seem to be applicable for quantitative estimation of scission/crosslinking ratios caused by irradiation of polystyrene. This is probably connected with deficiencies in the theoretical connection between radius of gyration and intrinsic viscosity in good solvents. Diallyl fumarate and diallyl maleate increased crosslinking rates, but only at low doses. Chain scission was enhanced by addition of 1,2‐dichloroethylene and 2,5‐dimethylhexane‐2,5‐dihydroperoxide.
Molecular complexes of sulfur dioxide with organic carbonates
Authors: Rooney M. L. , Best D. J. , Davis E. G.
Published: April 2003

Spectroscopic studies made on the bisphenol A polycarbonate–sulfur dioxide system showed evidence of interaction between polymer and penetrant. Equilibrium studies made on solutions of sulfur dioxide and organic carbonates chosen as monomer analogs showed that complexes of the donor–acceptor type were formed, and that at temperatures of 15°C and less the stoichiometry of these was greater than 1:1. The procedures described are compared with those used in other donor–acceptor studies, and the results observed from the equilibrium studies are interpreted by using data reported for other sulfur dioxide–donor systems.
Fibers from polyblends containing nylon 6 as basic component. I. Melt spinning and physical properties of blend fibers
Authors: Kitao Toshio , Kobayashi Hiroshi , Ikegami Seiji , Ohya Seigo
Published: April 2003

Five series of two‐component blend filaments, comprising nylon 6 (N6) and nylon 66 (N66), nylon 610 (N610), nylon 11 (N11), nylon 12 (N12), or poly(ethylene terephthalate) (PET), were prepared by using a research spinning machine and a conventional drawing machine. The microstructure and the physical properties of the resultant filaments were evaluated with a tensile tester, a optical microscope, a density‐gradient column, and a DTA instrument. When both components were mixed homogeneously so that they would form a three‐dimensional network, the tensile properties of the blend filament were at least equivalent to the values predicted from those of both components. On the other hand, as in the cases of 30/70 and 70/30 N6–PET, when the minor component was discretely distributed as short fibrils in the matrix of the major component, the blend filament had an extremely weak tenacity. A supertenacity filament was obtained from 50/50 N6–N610. The marked increase of the tensil strength and the initial modulus of 50/50 N6–N610, about 12 g/den and 520 kg/mm2, respectively, may be due to a significant increase in the crystallinity and the orientation of the blend.
Radiation‐induced copolymerization of isobutyl vinyl ether with trichloroethylene
Authors: Du Plessis T. A. , Thomas A. C.
Published: April 2003

The radiation‐induced copolymerization of isobutyl vinyl ether with trichloroethylene was investigated in the temperature range from −50°C to 100°C over a wide range of comonomer compositions. A copolymer was obtained in which the monomers alternate with regularity along the polymer chain over essentially the entire range of comonomer compositions. Both the rate of copolymerization and the number‐average molecular weight of the resulting copolymer were found to depend strongly on the initial comonomer composition. The monomer reactivity ratios were determined and correspond well with calculated values. An apparent activation energy of 3.2 kcal/mole was obtained for the copolymerization process which exhibits a dose rate dependence of 0.72. The number‐average molecular weight was found to be strongly dependent on the irradiation temperature, reaching a maximum value at 5°C.
Inorganic coordination polymers. XII. Chromium(III) tris(phosphinates)
Authors: Nannelli Piero , Block B. P. , King J. P. , Saraceno A. J. , Sprout O. S. , Peschko N. D. , Dahl G. H.
Published: April 2003

Cohesive films of a series of chromium(III) tris(phosphinates)[Cr(OPRR′O)(OPR″‐R‴O)(OPR*R**O)]y in which the side groups on the phosphorus are alkyl, phenyl, and/or hydrogen groups have been prepared by reaction casting or by hot pressing. The preparative reaction appears to involve conversion of an aquahydroxo or hydroxo chromium(III) bis(phosphinate) to an intermediate hydroxo bis(phosphinate) containing coordinated phosphinic acid followed by an intrachain reaction leading to the tris(phosphinate). Tensile strengths of the chromium(III) tris(phosphinates) range from 100 to 5600 psi, elongations from less than 1 to 100%. Thermogravimetric data indicate that major decomposition occurs at temperatures from 200 to 435°C in air and from 410 to 510°C in nitrogen. Infrared spectra and physical properties are interpreted to support a structure for the chromium(III) tris(phosphinates) which is based on linear, triple‐bridged chains. The presence of octyl or other long alkyl side groups on the phosphorus improves the physical properties, presumably by internal plasticization, but leads to decreased thermal stability.
Alternating copolymerization of dienes with α‐olefins
Authors: Furukawa Junji , Tsuruki Shigenori , Kiji Jitsuo
Published: April 2003

Alternating copolymerization of butadiene with several α‐olefins and of isoprene with propylene were investigated by using a mixture of VO(Acac)2, Et3Al, and Et2AlCl as catalyst. The alternating copolymerization ability of the olefins decreases in the order, propylene > 1‐butene > 4‐methyl‐1‐pentene > 3‐methyl‐1‐butene. The study on the sequence of the copolymer of isoprene with propylene by ozonolysis reveals that the polymer chain is reasonably expressed by the sequence \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} [{\rm CH}_{\rm 2} \hbox{--} {\rm CH} \hbox{=\hskip-1pt=} {\rm C(CH}_{\rm 3}) \hbox{--} {\rm CH}_{\rm 2} \hbox{--} {\rm CH(CH}_{\rm 3}) \hbox{--} {\rm CH}_{\rm 2} \rlap{--}]_n $\end{document}. NMR and infrared spectra indicate that the chain is terminated with propylene unit, forming a structure of C(CH3)CH2C(CH3)CH2 involving a vinylene group.
γ‐Radiolysis of ketone polymers. II. γ‐Irradiation of styrene–methyl vinyl ketone copolymers
Authors: Slivinskas J. A. , Guillet J. E.
Published: April 2003

γ‐Radiolysis of copolymers of styrene and methyl vinyl ketone shows that the introduction of pendant carbonyl groups markedly increases the G(s) value as compared to the homopolymer of styrene. The G(x) value is only slightly affected. These efficiencies are determined by employing an established statistical theory for random crosslinking and scission coupled with gel‐permeation chromatography as the analytical tool required to follow the changes in the MWD of polymers. Also the G(H2) values are unaltered by the introduction of carbonyl groups in polystyrene. These results are in marked contrast to the effects of carbonyl groups in polyethylene when subjected to γ‐radiolysis and can be attributed to the protective role played by the aromatic phenyl groups in polystyrene.
The influence of fine structure on the pyrolysis of cellulose. II. Pyrolysis in air
Authors: Basch A. , Lewin M.
Published: April 2003

The pyrolysis of purified celluloses in air at 251°C was studied. The pyrolysis was found to obey first‐order kinetics, and the rate constants correlated with the crystallinities, orientations and accessibilities of the samples. The results are interpreted in terms of an oxygen‐catalyzed decomposition, with the accessibility of oxygen to the cellulose determining the rate of pyrolysis. The production of levoglucosan under conditions approaching combustion was shown to be a function of the crystallinity and orientation of cellulose. Some levoglucosan appears to be produced from the less ordered regions.
Polymerization of methyl methacrylate initiated by tri‐n‐butylborane–organic halide systems
Authors: Yoshikuni M. , Asami M. , Iwabuchi S. , Kojima K.
Published: April 2003

The polymerization of methyl methacrylate (MMA) initiated by tri‐n‐butylborane (TBB) was studied in the presence of various organic halides (R′X). It was found that R′X accelerated the polymerization of MMA. Aliphatic halides were more effective than aromatic halides. Cocatalytic effects of butyl halides decreased in the order: n‐BuI > n‐BuBr > n‐BuCl; n‐BuBr ⋍ sec‐BuBr > i‐BuBr > tert‐BuBr. In the polymerization of MMA by TBB‐n‐BuI, the initial rate of polymerization was found to be proportional to the concentration of MMA and to the square root of the concentration of TBB‐n‐BuI. The apparent activation energy was 5.3 kcal/mole. From this and other results, it was assumed that the polymerization of MMA by this initiator system proceeds by a radical mechanism via a weak complex between TBB and R′X; alkyl radicals are formed by the interaction of R′X with TBB. The TBB–R′X system can initiate the polymerization of MMA and AN, but is ineffective in the polymerization of styrene.
Heat‐resistant polymers containing bipyridyl units. I. Polyimides
Authors: Kurita Keisuke , Williams Roy L.
Published: April 2003

Polyimides containing bipyridyl units were synthesized. The bipyridyl units were successfully incorporated by polymerization of various bipyridyl diamines with aromatic tetracarboxylic acid dianhydrides. The resulting polyamic acids had inherent viscosities in the range 0.07 to 2.26, and they were converted to the polyimides by thermal cyclization. The polyimides containing the bipyridyl units exhibited varying degrees of solubility in dimethylacetamide and m‐cresol and were found to be very soluble in dichloroacetic acid.
Photo‐copolymerization of methacryloyl‐L‐valine methyl ester, methacryloyl‐D‐valine methyl ester, and maleic anhydride
Authors: Nishihara Koji , Sakota Naokazu
Published: April 2003

Photocopolymerization of methacryloyl‐L‐valine methyl ester (L‐MAVM), methacryloyl‐D‐valine methyl ester (D‐MAVM) and maleic anhydride (MAn) was carried out in dioxane at 25°C without initiator at an initial total concentration of the three monomers of 1 mole/1.; the molar ratio of MAn in the feed to the sum of L‐ and D‐MAVM was 1 : 1 in all cases. The copolymer with a 1 : 1 molar ratio of MAVM and MAn was always obtained regardless of the feed molar ratio of L‐ and D‐MAVM. The circular dichroism (CD) spectra of the copolymer before and after hydrolysis showed a linear relationship between the monomer unit ellipticity at 222 nm and the molar feed ratio of L‐ and D‐MAVM and suggested the induction of an asymmetric center into the polymer main chain. The results also indicated that the configuration of the induced asymmetric carbon atoms would be arranged according to that of fed MAVM monomer.
Reaction of nitrogen dioxide with linear polyurethane
Authors: Jellinek H. H. G. , Wang T. J. Y.
Published: April 2003

Linear polyurethane has been exposed to nitrogen dioxide over a temperature range from 15 to 60°C at pressures of 20 and 2 mm Hg, respectively. Normal random‐chain scission of urethane links takes place accompanied by a limited amount of random crosslinking. These crosslinks are eventually irreversibly scissioned again. At the same time, carbon dioxide is evolved, and the infrared spectra of the polymer films change during exposure, indicating disappearance of urethane linkages and formation and decay of nitro and nitroso groups along the polymer backbone. The overall reaction is diffusion‐controlled at least down to a film thickness of 10 μ. All energies of activation of the various processes are relatively small as expected for a diffusion controlled process. Tentative mechanisms have been proposed agreeing well with experimental results.
Grafting onto wool. IV. Interaction of polymer radicals in the viscous media of wool fibers
Authors: Arai Kozo , Shimizu Masamichi , Shimada Machiko
Published: April 2003

In order to study the termination reaction of polymer radicals in the viscous media of wool fibers, reduced, methylated, and S‐carboxymethylated wool fibers were used for graft copolymerization of methyl methacrylate and styrene. With termination of poly(methyl methacrylate) radicals, two different termination reactions, recombination and disproportionation, were together involved in the grafting systems studied. The occurrences of two termination reactions in the system could be correlated with the mobility of the wool chain controlling the radical end mobility. With decreasing disulfide content in the fibers, disproportionation predominantly takes place among the mobilized chains. At a constant disulfide, the thiol content or the concentration of thiol anions becomes the determining factor for the termination reaction. A possible explanation for these phenomena in terms of the thiol and disulfide interchange reaction is presented. On the grafting of styrene, additional evidence was obtained that prevention and retardation of the interchange reactions followed mechanochemical bond scission of the disulfide and other covalent bonds and produced new free radicals which could initiate chain reactions.
Unsaturated condensation polymers by the friedel–crafts reaction
Authors: Huck P. J. , Pritchard G.
Published: April 2003

Reaction between stilbene and a difunctional ether, in presence of Lewis acid catalyst, produces low molecular weight condensation polymers containing substantial olefinic unsaturation. These resins have been studied by various analytical techniques. Some evidence is presented concerning structure. The condensation polymers are soluble in organic solvents and may be cross linked by free‐radical methods to form thermosetting networks.
Initial steps of thermal degradation of PVC prepared at various temperatures
Authors: Millan J. , Madruga E. L. , Bert M. , Guyot A.
Published: April 2003

PVC samples were obtained by bulk polymerization initiated with AIBN and ultraviolet irradiation at 40, 25, 0, −30, and −50°C. They were characterized by 13C NMR measurements, infrared spectroscopy, GPC in hexamethylphosphoramide and B.E.T. surface area measurements. Their thermal degradation was studied between 110 and 185°C by using continuous titration of HCl evolved through a conductimetric cell. The ultraviolet spectra were recorded at various steps of the degradation. At high degradation temperatures, the more syndiotactic the polymer, the longer the polyene average sequences are. The amount of HCl evolved is minimum for a polymerization temperature of 0 or 25°C, depending on the degradation temperature and on the morphology of the polymer. The results are discussed in terms of chemical factors (tacticity distribution, molecular weight) as well as of physical factors (morphology, interval viscosity).
Absorption currents and photocurrents in polyethylene
Authors: Wintle H. J. , Tibensky G. M.
Published: April 2003

It is shown that an optically excited current in polyethylene does not interact with the dark absorption current. This implies that the carriers are different for the two processes. We suggest that holes are photo‐injected and traverse the full thickness of the specimen, while the absorption currents are due to surface barrier processes, as proposed by other workers.
Drawing of nylon 6 fibers (bristles)
Authors: Sakaoku K. , Morosoff N. , Peterlin A.
Published: April 2003

By means of electron microscopy of surface replicas and both small‐angle and wide‐angle x‐ray scattering, nylon 6 fibers were investigated in the as‐spun state, after drawing at 180°C to a draw ratio up to 4.95, and after subsequent annealing. As spun, the fiber exhibits a small fraction of row‐nucleated cylindrites and a great many spherulites (with an average diameter of a few microns) side by side. Drawing deforms the spherulites into spindle‐shaped structures (λ = 2) and subsequently produces well‐aligned microfibrils. Small‐angle x‐ray scattering yields a two‐point diagram at small λ and a fourpoint diagram at high λ. The long period seems to decrease slightly with draw ratio. Annealing at temperatures above the temperature of drawing increases the long period to a greater extent with samples of lower λ. The crystal lattice orientation is nearly complete at λ = 4.95.
Tetrachlorobisphenol‐A adipate polymers. I. Crystallization of poly(tetrachlorobisphenol‐A adipate)
Authors: Lanza E. , Berghmans H. , Smets G.
Published: April 2003

The properties of melt‐crystallized poly(tetrachlorobisphenol‐A adipate) were studied by using a differential scanning calorimeter. The dependence of melting point and the degree of crystallinity are reported as a function of the crystallization conditions. The heat of fusion is equal to 8.1 kcal/mole, while the equilibrium melting point, as determined by extrapolation, is 283°C. The polymer crystallized from the melt has a maximum degree of crystallinity of 0.53.
Heterogeneous nucleation in the crystallization of polyolefins. III. Theory and mechansim
Authors: Binsbergen F. L.
Published: April 2003

The nucleating activity of a large number of nucleating agents for the crystallization of polyolefins is not based on a high surface free energy of the substrate or on epitaxy, or on a minimum particle size just compatible with the thickness of the crystallizing polymer lamellae, or on any persistance of crystalline material in holes of the nucleating particles. The relevant mechanism is thought to be nucleation at steps of limited length in the surface of the nucleating particles. The nucleation is enhanced by a high degree of accommodation of polymer molecules at the surface of the substrate through the presence of ditches in the latter which cause prealignment of polymer chains and thus facilitate crystallization.
Crystal structure of α‐gutta percha: Modification of the constrained least‐squares method
Authors: Takahashi Yasuhiro , Sato Takefumi , Tadokoro Hiroyuki , Tanaka Yasuyuki
Published: April 2003

The crystal structure of α‐gutta percha has been determined by x‐ray diffraction. The unit cell parameters are a = 7.98 Å, b = 6.29 Å, c (fiber period) = 8.77 Å, and β = 102.0° (monoclinic). The space group is P21/c–C2h5. Two molecular chains of nearly trans‐CTS‐trans‐CTS̄ conformation pass through a unit cell; C, T, S, and S̄ being the cis, trans, and two types of skew forms, respectively. The constrainedle astsquares method was modified so that the order of the least squares matrix could be reduced and was applied to the refinement of the crystal structure.
Melting behavior of ethylene oxide–propylene oxide (sym‐PEP) block copolymers
Authors: Booth C. , Pickles C. J.
Published: April 2003

Melting points and lamellar thicknesses have been measured for ethylene oxide–propylene oxide block copolymers (sym‐PEP) with central poly(ethylene oxide) block lengths of 70–100 chain units and end poly(propylene oxide) block lengths of 0–30 chain units. Melting points of the block copolymers are lower than those of the corresponding poly(ethylene oxide) homopolymer by an amount (up to 15°C) which increases as the poly(propylene oxide) block length increases. Most samples have more than one melting transition, which can be assigned to variously folded chain crystals. End interfacial free energies σe for the various crystals have been estimated by use of Flory's theory of melting of block copolymers. For a given crystal type (e.g., once‐folded‐chain) σe is higher the longer the chain length of the end poly(propylene oxide) blocks. For a given copolymer σe is lower, the more highly folded the poly(ethylene oxide) chain.
Melting behavior of ethylene oxide–propylene oxide (sym‐EPE) block copolymers
Authors: Booth C. , Dodgson D. V.
Published: April 2003

Melting points have been measured for several ethylene oxide–propylene oxide block copolymers (sym‐EPE) chosen from the Pluronic range. Melting points of the block copolymers are lower than those of the corresponding poly(ethylene oxide) homopolymer by up to 4°C. The melting point depressions are much smaller than those observed for comparable sym‐PEP block copolymers.
Elastomeric adhesives: Effect of cross link density on joint strength
Authors: Andrews E. H. , Kinloch A. J.
Published: April 2003

The dependence of joint strength upon the molecular weight between crosslinks Mc of an adhesive has been investigated for joints which consist of a crosslinked, amorphous rubber adhering to a rigid polymeric substrate. The joint strength was found to be independent of Mc if results were compared at the same effective rate of testing. If, however, values of joint strength were compared at a particular test temperature and rate, the joint strength generally increased as the value of Mc decreased. This result can be explained by the increase of the glass transition temperature of the adhesive with increasing crosslink density.
Microbial degradation of polymer solids. I. Cellophane
Authors: Engler P. , Carr S. H.
Published: April 2003

Specimens of regenerated cellulose films (cellophane) have been inoculated with cellulolytic fungi and the resulting degradation monitored through change in physical properties. Investigation of structure–property relationship in cellophane have revealed that surface microfibrils are highly oriented parallel to the manufacturing machine direction, while those in the film interior exist in a somewhat disordered array. Cellulase enzymes have been observed to diffuse appreciable distances from their point of application and to attack disordered regions more readily than the crystallites. Damage to surface microfibrils appears to involve their being cleaved into short segments. The fungus studied in this work forms a network of hyphae that covers much of the specimen surface soon after growth starts; hyphae penetrate into the film and proceed to remove its core more rapidly than surface layers. Tensile strength declines progressively as this degradation occurs, but vapor barrier properties remain essentially unchanged over the period of these studies. The suggests that intrusion of hyphae, in combination with enzymatic digestion of cellulose, rapidly lowers load‐bearing characteristics, but moisture permeation rates stay nearly constant owing to the presence of fungal material at sites where cellulose has been removed.
Dilute solution properties and molecular characterization of poly(butyl methacrylate‐co‐styrene)
Authors: Srinivasan K. S. V. , Santappa M.
Published: April 2003

Dilute solution properties of fractionated poly(butyl methacrylate‐co‐styrene) PBMAS prepared by bulk polymerization, have been investigated by means of light scattering, viscometry, and osmometry. As the composition heterogeneity was narrow, the characterization of the copolymer was effected in a single solvent by light scattering. Infrared and nuclear magnetic resonance spectra were used to determine the composition and sequence distribution of monomer units of the copolymer. The molecular weight dependence of the limiting viscosity number and of the root‐mean‐square end‐to‐end distance have been established. The Mark‐Houwink relation showed that methylethyl ketone is a good solvent compared with cyclohexane. The validity of various extrapolation procedures that have been proposed to calculate the unperturbed dimensions have been examined. Root‐mean‐square end‐to‐end distances have been calculated from the Debye‐Bueche and Kirkwood‐Riseman methods and compared with the experimental values. The molecular weight dependence of the second virial coefficient agreed well with that calculated from the Orofino‐Flory equation. The value of the steric hindrance parameter σ for the copolymer has been found to be 2.27 compared to 2.05 for poly(butyl methacrylate) and 2.22 for polystyrene, which indicates that PBMAS is a stiffer chain in solution than those of the constituent homopolymers.