bluuebunny/crossref_metadata_2025 huggingface dataset:
Singlet oxygen and photooxidation of polymers
Authors: Ivanov V. B. , Shlyapintokh V. Ya.
Published: April 2003

The rates of accumulation of oxygen‐containing species in photooxidation have been determined for a series of polymers such as polystyrene, polyisoprene, and polybutadiene in a wide range of singlet oxygen stationary concentrations in the polymers. An increase in singlet oxygen (1O2) concentration was achieved by introducing a dye which is a 1O2 donor into a polymer and by irradiating a sample with an additional source of light absorbed by the dye only. To decrease 1O2 concentration, 1,2,5‐trimethyl‐4‐hydroxyphenylpiperidine, which is a quencher of 1O2, was introduced into a sample. The 1O2 stationary concentration in an oxidized polymer was measured via singlet oxygen oxidation of 2,2,6,6‐tetramethyl‐4‐oxypiperidine which leads to the formation of the corresponding nitroxyl radical. The photooxidation rate has been found to vary only slightly with 1O2 concentration, even when the concentration changes 10–25‐fold. Thus, 1O2 does not participate appreciably in the process of polymer photooxidation. It may be due to the lowering of 1O2 reactivity toward unsaturated groups in the polymer matrix as compared with that in solution.
ESCA applied to polymers. XVIII. RF glow discharge modification of polymers in helium, neon, argon, and krypton
Authors: Clark D. T. , Dilks A.
Published: April 2003

The crosslinking of an ethylene–tetrafluoroethylene copolymer by exposure to a variety of inert gas plasmas, excited by an inductively coupled radiofrequency (RF) field, has been studied. The rates for direct and radiative energy‐transfer processes are determined within the framework of a kinetic model of the system and are shown to have a strong dependence on the sustaining gas, as do the average depths of penetration of the ions and metastable species. Helium is found to be the most efficient gas for the crosslinking of the outermost few monolayers whereas the crosslinking of the subsurface and bulk polymer is best effected by neon. Madelung charge potential calculations have been performed to simulate the experimentally determined x‐ray photoelectron spectroscopy (ESCA) spectra to elucidate several features of the mechanisms involved.
A pronounced ortho effect in the polymerization of o‐substituted β‐nitrostyrenes
Authors: Carter Mary E. , Drueke Joseph W. , Nash James L. , Schwietert James W. , Butler George B.
Published: April 2003

It was shown in a previous paper that a number of m ‐ and p‐substituted β‐nitrostyrenes would readily undergo polymerization via anionic initiation with alkoxide ions to yield high polymers, whereas, in all cases, the corresponding o‐substituted isomers could not be induced to produce polymers under any conditions tried. This article reports a systematic study of this unexpected “ortho effect” based on the initial postulate that the effect was the result of steric inhibition of the propagation step that would ordinarily lead to polymer. Since the fluorine atom is only slightly larger than the hydrogen atom, the series o‐, m‐, and p‐fluoro‐β‐nitrostyrenes was synthesized and its alkoxide ion‐initiated polymerization studied. Although it was shown in all cases of o‐substituted β‐nitrostyrenes studied that initiation was rapid, only in the case of o‐fluoro‐β‐nitrostyrene was a substantial amount of polymer obtained. With up to 3 mole % initiator a maximum of 26% polymer was obtained, whereas polymerization was rapid in cases of the meta and para isomers. The values of the propagation rate constants kp were found to be 1.1 liters/mole‐sec for the para isomer as compared with 4.8 × 10−2 liter/mole‐sec for the ortho isomer for a ratio kp(p)/kp(o) = 23, the magnitude of this ortho effect for the fluorine atom.
The kinetics of polyesterification. II. Succinic acid and ethylene glycol
Authors: Lin Chen Chong , Yu Ping Chang
Published: April 2003

The polyesterification of succinic acid with ethylene glycol in both equimolar and nonequimolar ratios was investigated at the reaction temperature of 195°C. The experimental results agreed quite well with the kinetic equations proposed in our previous paper for the adipic acid–ethylene glycol system, except in the case of acid‐catalyzed equimolar reaction, where a shift of kinetic behavior from reaction control to diffusion control would appear. The apparent rate constants for uncatalyzed and acid‐catalyzed reactions were evaluated by using the method of least squares for various values of initial molar ratio between [OH] and [COOH]. The dissociation effect of hydrogen ion from dibasic acid in glycol, as proposed in the adipic acid–ethylene glycol system, could also be applied in the succinic acid–ethylene glycol system to explain the kinetic behavior observed. The kinetic equations previously proposed for polyesterification were again confirmed.
Radical polymerization of various alkyl methacrylates in liquid crystalline solvents
Authors: Tanaka Yoshio , Yamaguchi Fumio , Shiraki Masaru , Okada Akira
Published: April 2003

The polymerization of methacrylates of methyl, ethyl, butyl, hexyl, octyl, dodecyl, and octadecyl alcohols was studied with 2,2′‐azobisisobutyronitrile in the smectic, nematic, cholesteric, and isotropic liquid phases at 50–75°C. N‐(4‐Methoxyphenylmethylene)phenylamine, N‐(4‐ethoxyphenyl‐methylene)‐4‐butylphenylamine, cholesteryl octadecanoate, and benzene were used as the solvents. The viscosities of the polymers were enhanced in the mesomorphic solvents. The polymer was converted to the corresponding poly(methyl methacrylate) through hydrolysis and esterification. Tacticities of the resultant poly(methyl methacrylates) were determined by nuclear magnetic resonance spectroscopy. The isotacticities of the polymers obtained in the smectic and the nematic phases were basically the same and appeared to be larger than those of the polymers in the cholesteric and isotropic liquid states. The polymerization of the methacrylates of butyl and longer‐chain alcohols deviated from Bernoullian statistics and gave polymers more isotactic than those of methyl and ethyl methacrylates.
Effect of photooxidation of polystyrene on its dielectric properties. II. Use of dielectric loss measurements to study photooxidation
Authors: Weir N. A.
Published: April 2003

Dielectric loss measurements have been applied to study the short‐wave (λ = 254 nm) and long‐wave (λ > 300 nm) photooxidation of polystyrene which had been prepared using both free radical and anionic initiator. The high‐frequency loss peak, attributable to carbonyl products of oxidation is a sensitive monitor of the rate of oxidation, the sensitivity being greater than that of manometric measurements. The data are specific to carbonyl compounds and the technique is particularly suitable for studying the surfaces, on which most of the above photooxidation occurs with polystyrene. Effects of radiation intensity and oxygen pressure were also studied. The measurements have permitted a more detailed study of the long‐wave photooxidation process than has previously been undertaken, and the results emphasize differential reactivities of radically and anionically prepared polymers. Results are interpreted in terms of initiation by both impurities and charge‐transfer complexes.
Polymerization of aromatic nuclei. XVIII. Polymerization of benzene to poly‐p‐phenylene by aluminum chloride–air–water
Authors: Durham Judith E. , McFarland Kathryn N. , Kovacic Peter
Published: April 2003

Although the reaction of benzene with aluminum chloride has been quite thoroughly examined by prior investigators, the present report is the first one on formation of poly‐p‐phenylene in this system. Optimum conditions, which gave low yields, involved 7 days at 49–51deg;C. The presence of oxygen (oxidant) and presumably water (cocatalyst) was necessary in order for polymerization to occur. Physical and chemical properties, e.g., behavior toward Br2 and H2O2–CH3CO2H, indicate that the polymer structure is slightly different from that of the material from C6H6–AlCl3–CuCl2. The polymer from C6H6–AlCl3 may possess a lower molecular weight and exhibits a greater degree of structural irregularity in the form of dihydrobenzene, p‐quinoid, or polynuclear regions. In the chemical studies, various compounds were used as models (tetrahydroquaterphenyl, triphenylene, and lower p‐polyphenyls).
General molecular weight‐lowering side reaction in the thermal condensation of aromatic methyl esters with aromatic amines and hydrazides
Authors: Flannigan Jerry E. , Mortimer George A.
Published: April 2003

The direct thermal condensation of aromatic methyl esters with aromatic amines and hydrazides was studied. Using model compounds, it was learned that N‐methylation of amines (both aromatic and aliphatic) and hydrazides is inherent at temperatures required for condensation polymerization. This side reaction prevents attainment of high molecular weight polyamides, polyhydrazides, or polyoxadiazoles from the corresponding difunctional aromatic monomers by heat alone. Reported catalysts for the condensation reaction do not prevent the side reaction.
Esterolytic activity of imidazole‐containing polymers. Hydrophobic influences in copoly[1‐alkyl‐4‐ or 5‐vinylimidazole/4(5)‐vinylimidazole]‐catalyzed hydrolysis of 3‐nitro‐4‐acyloxybenzoic acids
Authors: Overberger C. G. , Kawakami Y.
Published: April 2003

Water‐soluble copolymers containing imidazole and N‐alkylated imidazole pendant groups have been synthesized in order to investigate the hydrophobic interactions between polymeric catalysts and long alkyl chain ester substrates. Copoly[1‐methyl‐4‐vinyl‐imidazole/4(5)‐vinylimidazole],copoly[1‐methyl‐5‐vinylimidazole/4(5)‐vinylimidazole], copoly[1‐ethyl‐5‐vinylimidazole/4‐(5)‐vinyl‐imidazole] and copoly[1‐propyl‐5‐vinylimidazole/4(5)‐vinylimidazole] were synthesized and their catalytic activity toward 3‐nitro‐4‐acyloxybenzoic acid substrates (Sn−) was determined in 28.5% ethanol–water and in water and compared with that of the mixtures of homopolymers. Hydrophobic interactions were important for rate enhancement of the hydrolysis of long‐chain ester substrates compared to that of short‐chain ester substrates. The copolymers catalyzed the hydrolysis of 3‐nitro‐4‐dodecanoyloxy‐benzoic acid (S12−) about two times faster than the mixtures at pH 7.11 in 28.5% ethanol–water. The hydrolysis of S12− by the copolymers was about five times faster in water than 28.5% ethanol–water.
Anionic polymerization with alkaline‐earth counterion. I. Preparation and characterization of dicarbanionic oligostyrylbarium and ‐strontium in tetrahydrofuran
Authors: Mathis Claude , Christmann‐Lamande Lydia , François Bernard
Published: April 2003

Dicarbanionic oligostyrylbarium or ‐strontium, PS=Ba++ and PS=Sr++, were prepared by reacting styrene with finely divided barium or strontium in THF or THP. The effects of reaction temperature, monomer, and metal concentration were described. Difunctionality of these living oligomers is confirmed from calculated and observed molecular weight data and also from conductivity measurements. λmax of carbanions is found to vary with DP. At 25°C it decreases from 368 nm for dimers to 359 nm for DP > 10. As observed for monocarbanionic polystyrylbarium (PS−)2Ba++, λmax of PS=Ba++ of high DP decreases with temperature, while λmax of PS=Ba++ of low DP increases with decreasing temperature. At −100°C the difference between the two extreme values is about 30 nm. Similar results are obtained with PS=Sr++. Such unusual spectral properties are interpreted, on the basis of excitation molecular theory, in terms of ring structures for the living oligomers.
Haloaldehyde polymers. IX. Polybromodichloroacetaldehyde
Authors: Lipp D. W. , Vogl O.
Published: April 2003

Bromodichloroacetaldehyde was synthesized by two methods. The first synthesis started from chloral, which was allowed to react with Ph3P and the resultant compound brominated and hydrolyzed to give bromodichloroacetaldehyde in an overall yield of 60%. Purification by repeated distillation from P2O5 gave polymerization grade bromodichloroacetabldehyde. Bromodichloroacetaldehyde could also be synthesized by bromination of dichloroacetaldehyde diethyl acetal. The yields of this synthesis were only 20–30%, and the aldehyde could not be purified readily to give polymerization grade monomer. Bromodichloroacetaldehyde could be homopolymerized at −30°C with anionic and also some cationic initiators to a polymer which was insoluble and did not melt but degraded to monomer above 200°C. The ceiling temperature of the polymerization was −15°C in 1M solution. Bromodichloroacetaldehyde could also be copolymerized with isocyanates, primarily aryl isocyanates, and also with chloral.
ESCA applied to polymers. XXI. Investigation of sample‐charging phenomena
Authors: Clark D. T. , Dilks A. , Thomas H. R.
Published: April 2003

Sample‐charging phenomena arising in the ESCA experiment have been investigated for a series of polymers. For samples studied as films or powders mounted insulated from the spectrometer probe and for gold under similar conditions it is shown that over a wide range of operating conditions, equilibrium charging shifts are characteristic of the sample and show a strong dependence on the theoretically calculated total photoionization cross sections. The surface sensitivity of the phenomenon has been demonstrated by monitoring changes in charging shifts as a function of hydrocarbon contamination. For polymer films mounted directly in contact with the spectrometer, the charging shifts exhibit time‐dependent behavior. The utility of studying sample‐charging shifts as an interesting phenomenon in its own right is demonstrated by reference to changes which occur consequent upon surface modification of an ethylene–tetrafluoroethylene copolymer system in RF plasmas excited in inert gases.
Charge‐transfer complexes as polymerization inhibitors. I. Amine–chloranil complexes as inhibitors for the radical polymerization of methyl methacrylate
Authors: Yassin Ahmady A. , Rizk Nadia A.
Published: April 2003

Charge‐transfer complexes of N,N‐dimethylaniline (DMA) and triethylamine (TEA) with chloranil have been investigated as inhibitors for the sensitized polymerization of methyl methacrylate (MMA) in bulk and in solution. Complete inhibition is achieved by the complexes of both amines followed by retardation only in case of DMA. The higher inhibiting efficiency of the TEA complexes is attributed to their greater stability. The polymers formed in the presence of chloranil alone or its complexes with both amines are quinonoid and contain no combined nitrogen. The results support the idea that inhibition reaction involve electron transfer from the growing chains to the quinone, with formation of molecular complexes of polymeric cations and semiquinone anions. The latter are the actual inhibiting species, so that the efficiency of inhibiting depends on their concentration, which is determined by the stability of the molecular complexes formed. The inhibition reactions should accordingly be considered as oxidation–reduction processes in which the growing chains are the electron donors. The suggested mechanism affords an explanation for the great differences in the inhibiting power of a particular quinone for the polymerization of different monomers.
Polymerization of oriented monomers. II. Polymerization of 4‐vinylpyridine perchlorate in micellar aggregates
Authors: Paleos C. M. , Dais Photis
Published: April 2003

Polymerization of 4‐vinylpyridinium perchlorate (I) is studied under isotropic and anisotropic conditions. Anisotropy or orientation of I may be achieved by micelle formation in concentrated aqueous or acid solutions, i.e., above the monomer's critical micelle concentration (CMC). Some properties of the isotropically and anisotropically obtained polymers are comparatively studied with the emphasis placed on the elucidation of their structure by 13C‐NMR spectroscopy. By the same spectroscopic technique the microstructure of 1,2‐polymer is further investigated in conjunction with the proposed polymerization model. It is concluded that polymer structure is affected by the organization of the monomers into micelles whereas their microstructure is not.
Thermal degradation of the polyurethane from 1,4‐butanediol and methylene bis(4‐phenyl isocyanate)
Authors: Grassie N. , Zulfiqar M.
Published: April 2003

A polyurethane prepared from 1,4‐butanediol (BD) and methylene bis(4‐phenyl isocyanate) begins to evolve volatile degradation products at approximately 240°C. By a combination of thermal analysis methods (TVA, TG, and DSC) and examination of the volatile and involatile products by using a combination of GLC and infrared and mass spectrometric analysis, it is shown that the total reaction comprises a primary depoly‐condensation process in which the two monomers are formed, followed by the subsequent reaction of these monomers to form the volatile products, tetrahydrofuran, dihydrofuran, carbon dioxide, water, butadiene, hydrogen cyanide, and carbon monoxide and residual carbodiimide and urea structures. A mechanism, which accounts for all these products, has been formulated and tested.
Diffusion effects in the oxidative degradation of vulcanized rubbers. II. Transient rate of chain scission
Authors: Ono K. , Kaeriyama A. , Murakami K.
Published: April 2003

The effect of diffusion in the oxidative degradation of cis‐1,4‐polyisoprene vulcanizates was estimated by the analysis of the transient state of diffusion and oxidative degradation. An expression for the number of network chain scissions was obtained by solving the diffusion equation, which takes into account first‐order oxygen consumption as well as constant scission efficiency. A practical method was proposed to analyze the transient process, which makes it possible to estimate diffusion coefficient and first‐order rate constant independently. It was shown that the same analytical procedure would be applicable to the concentration jump method. The diffusion coefficient thus obtained was somewhat lower than the extrapolated value from the low‐temperature data which was obtained in the absence of oxidation. Possible reasons responsible for this discrepancy were discussed.
Constitution moléculaire d' α,ω‐difluoro‐μ‐oxo‐poly(méthylphosphanoxy diméthylsilanes): Mise en evidence d'une forte tendance à l'alternance régulière des centres siliciés et phosphorés à l'equilibre
Authors: Pace Simonne C. , Riess Jean G.
Published: April 2003

The purpose of this study was to gain a closer knowledge of the molecular constitution of the linear fluorine‐terminated oxygen‐bridged methylphosphanoxy/dimethylsilane polymers, for example, to find evidence for preferential sorting (or, on the contrary, for random scattering) of the substituents and building units. The title polymers were prepared by reaction of MeP(O)F2 with cyclic dimethylsiloxanes (Me2SiO)n (n = 3 or 4). An equilibrium is reached in the redistribution of fluorine vs. bridging oxygen atoms among the phosphorus and silicon‐based centers, and among the resulting building units, after about 2 months at 120°C. The excellent resolution of the 1H‐NMR spectra (Fig. 2), even at 60 MHz, allowed identification of seventeen different fragments (Table II). Nineteen equilibrated samples of varied overall compositions (R = F/(Si + P); R′ = P/(Si + P)) have been analyzed (Table IV), and their molecular constitution is described by a set of four basic constants. The fundamental features which govern the structure of these polymers are as follows. (a) The regular (Si‐O‐P) alternation of the two different centers, which is thermodynamically favored, as shown by the linkage constant K0 = [Si‐O‐Si][P‐O‐P]/[Si‐O‐P]2 ≃ 104, which describes the sorting of the silicon and phosphorus atoms on the bridging oxygens, and which deviates by four orders of magnitude from its random value of 0.25. (b) A somewhat surprising lack of preferential distribution of fluorine and oxygen between the two centers (KI = [MeP(O)F2][Me2SiO1/2]2/[Me2SiF2]‐[MeP(O)(O1/2)2]) differs little from (a), which contrasts with the preferential affinity of fluorine for silicon and oxygen for phosphorus (KI ≃ 107) that was found when F atoms and OCH3 groups were exchanged between the same centers. (c) The sorting of the fluorine atoms and oxygen bridges on each center, to give neso molecules and the terminal and medium building units, resulting in a slight preference for the formation of the terminal units, as expressed by
Bulk polymerization of methyl methacrylate electroinitiated by tetrabutylammonium salts
Authors: Pistoia Gianfranco , Ingo Gabriel Maria
Published: April 2003

The radical electroinitiated polymerization of methyl methacrylate has been performed in solutions of tetrabutylammonium salts. TBANO3 is by far the most efficient, because of the relatively low anodic potential required for the oxidation to the radical. The influence of factors such as temperature, current density, and salt concentration on yields and molecular weights has been examined. The absence of a gel effect allows the onset of a steady state in which the polymerization rate is first‐order with respect to monomer.
Study of gel formation in the polycyclotrimerization reaction as typified by polycyanate synthesis
Authors: Korshak V. V. , Pankratov V. A. , Ladovskaya A. A. , Vinogradova S. V.
Published: April 2003

The process of gel formation in the reaction of polycyclotrimerization of 2,2‐bis(4‐cyanatophenyl) propane has been studied as a function of the nature of solvent, monomer concentration, kind and concentration of catalyst, temperature of the process, and the way in which the reaction is conducted. The gel point and the dependence of the gel yield on the degree of the system conversion vary with the conditions of the process conduction and the solvent used. It was found also that the type of the catalyst affects the parameters indicated above only in certain solvents. A change in the monomer concentration has been found to affect differently the gel point of the system, depending on the nature of the solvent. The experimental data obtained have been compared with the results of the theory of gel formation developed for the process of polycyclotrimerization by Fukui and Yamabe. The dependence of the process kinetics on the type and concentration of catalysts has been investigated. No marked influence of temperature on the regularities of gel formation has been disclosed.
Surface grafting of polyethylene by mutual irradiation in methyl acrylate vapor. I. γ irradiation
Authors: Yamamoto Fumio , Yamakawa Shinzo , Kato Yoshinori
Published: April 2003

Mutual irradiation of polyethylene (PE) in methyl acrylate vapor easily forms a poly(methyl acrylate) (PMA) homopolymer layer on the inner graft copolymer layer consisting of both PE and PMA components as a result of the rapidly increasing surface‐graft composition. This growth process of surface grafting has been found to provide some specific kinetic features different from those in other surface‐grafting systems. With formation of the surface homopolymer layer, low‐ and highdensity PE sheets give the same grafting rate, whereas both sheets give different rates in grafting stages or conditions in which the homopolymer layer is not formed. This result indicates that most monomers, penetrating across the surface, are entrapped or consumed in the surface homopolymer layer; accordingly the rate becomes independent of the type of PE sheets that have significantly different diffusion coefficients. The thickness of the inner graft copolymer layer, which is kept constant after homopolymer‐layer formation, increases with decreasing dose rate and with increasing monomer vapor pressure and temperature. This behavior can be qualitatively explained according to an equation for the initial steady‐state grafting depth.
Poly(carbon suboxide): A photosensitive paramagnetic ladder polymer
Authors: Yang N.‐L. , Snow A. , Haubenstock H. , Bramwell F.
Published: April 2003

Carbon suboxide was found to give, on photo‐ and thermal‐polymerization, a photosensitive paramagnetic polymer. Studies of the kinetics of the ESR signal growth accompanying the polymerization process complement documented results obtained from monitoring the rate of polymer production and monomer disappearance. The spin concentration of the polymer increases with higher reaction temperature, reaching 2 × 1019 spin/g at a polymerization temperature of 105°C. The paramagnetism of poly(carbon suboxide) follows the Curie—Weiss law. Relaxation behavior at room temperature and g values for the spin systems have been obtained. The 105°C polymer shows a Weiss constant equal to 17°K and an extremely narrow ESR line width, ca. 10 mG, at 5°K. The 13C coupling constant from the selectively labeled polymer indicates π‐electron delocalization over the ladder polymer. The polymer paramagnetism can be further reversibly enhanced by visible light irradiation. The steady‐state concentration of the photo‐ESR signal is proportional to the square root of incident light intensity, with a quantum yield at room temperature for charge accumulation equal to 5% at an incident light level of 1015 photons/sec‐cm2. Fluorescence and excitation spectra of the soluble fraction of poly(carbon suboxide) are presented together with the quantum yield. The polymer has also been found to be an effective photopolymerization initiator at wavelengths longer than 340 nm.
Synthesis and property comparisons of random and alternating hybrid fluorocarbon–fluorosilicone copolymers
Authors: Riley M. O. , Kim Y. K. , Pierce O. R.
Published: April 2003

The synthesis of a number of random and alternating copolymers of a fluorosiloxane and a hybrid fluorocarbon‐fluorosiloxane are described, along with property comparisons. The random copolymers were prepared by silanol–chlorosilane condensation, while the alternating copolymer preparation involved the use of the novel silanol—silyl‐N‐methylacetamido condensation reaction, which was used to produce a high polymer, M̄n = 260,000. The physical properties of the two classes of polymers which were compared include: glass transition temperatures, reversion resistance, and thermal and oxidative weight loss. From these comparisons, it was possible to gauge the relative effects of backbone architecture, as well as monomer ratios, upon copolymer properties. Comparison of the thermogravimetric analysis (TGA) of both the random and alternating LS/FCS copolymer systems with the parent LS and FCS homopolymers indicates that the copolymer generally show little variation among themselves, but better thermal characteristics than either of the parents.
Particle nucleation in emulsion polymerization. I. A theory for homogeneous nucleation
Authors: Hansen F. K. , Ugelstad J.
Published: April 2003

This paper is the first in a series intended to clarify the particle nucleation mechanisms in emulsion polymerization. The theory for particle nucleation by precipitation of oligomeric radicals from the water phase is discussed and a model based on the diffusion, propagation and termination steps is presented. The physical factors that influence the capture rate of oligomers in particles are discussed, and qualitative expressions for the electrostatic repulsion and reversible diffusion are derived. These factors are shown to be able to explain the relatively slow absorption rate of oligomers in particles and micelles. A kinetic model for simultaneous particle nucleation and limited flocculation is presented. Numerical integration of this model shows that the particle number goes through a maximum and that simultaneous nucleation and flocculation of primary particles may take place after Interval I in an emulsion polymerization is finished.
Multichain copoly(α‐amino acid). II. Preparation and properties of multi‐Nϵ‐poly(γ‐benzyl‐L‐glutamyl)copoly(L‐lysine γ‐methyl‐L‐glutamate)
Authors: Sakamoto Munenori , Kuroyanagi Yoshimitsu , Sakamoto Ryuichi
Published: April 2003

A number of multi‐Nϵ‐poly(γ‐benzyl‐L‐glutamyl)copoly(L‐lysine γ‐methyl‐L‐glutamate)s with branches having various degrees of polymerization and with various intervals of the grafting sites in the core molecule were prepared in N,N‐dimethylformamide containing dimethyl sulfoxide by the reaction of N‐carboxy anhydride of γ‐benzyl L‐glutamate with random copoly(L‐lysine γ‐methyl‐L‐glutamate)s of different composition with various anhydride‐initiator ratios. The relationship between the intrinsic viscosity measured in a coil solvent, dichloroacetic acid (DCA), and the number‐average molecular weight determined by osmometry was found to be expressed by the Mark–Houwink–Sakurada equation for the multichain copoly(α‐amino acid)s which were made from the same polymeric initiator. The observed α values of the multichain copoly(α‐amino acid)s in the equation were lower than that of linear poly(γ‐benzyl‐L‐glutamate). The solvent induced helix–coil transition of the multichain copolymer was investigated in the chloroform‒DCA system by the ORD technique. Two kinds of transition regions were clearly distinguished: The α‐helices of the core molecules underwent the transition at lower DCA concentration and those of the branch chains at higher DCA concentration. The reduced viscosity of the multichain copoly‐(α‐amino acid) increased slightly between the two transition regions, in contrast to the large decrease in the reduced viscosity of linear poly(γ‐benzyl‐L‐glutamate) during the helix–coil transition.
Modification of poly(vinyl chloride). XXXI. Crosslinking of poly(vinyl chloride) with 2‐R‐4,6‐dithiol‐s‐triazine and metal activators
Authors: Mori Kunio , Nakamura Yoshiro
Published: April 2003

Crosslinking of poly(vinyl chloride) (PVC) with 2‐R‐4,6‐dithiol‐s‐triazine (R‐DT) and metal activators has been studied to determine crosslinking rate constants, induction periods, and apparent activation energy and the final efficiency of crosslinking agents. The rate constants were about 1.4–7.5 min−1 and the induction periods were about 6.8–24.3 min for various kinds of R‐DT at 180°C. The activation energy was about 16.6–33 kcal/mol over the temperature range 160–195°C.

The rate constants were strongly influenced by 2‐substituted groups (R) in R‐DT and increased in the order R′O‐≪ R′NH‐< (R′)2N, where R′ is an alkyl or aryl group. Further, the rate constants increased in the order of: metal carboxylates < metal carboxylates < metal oxides for the activators and in the order of: Pb < Mg < Ca < Ba < Na for metal atoms.

The final efficiency was about 75–80% for the activators such as MgO, MgCO3, PbO, and SnO. The activators containing Na, Ca, and Ba atoms, however, gave final efficiency of more than 100%.
Oxidative stress relaxation and the measurement of sol fraction in rubber vulcanizates
Authors: Kaeriyama Akitoshi , Ono Katsumichi , Murakami Kenkichi
Published: April 2003

A simple method to determine the chain scission mechanism of the oxidative degradation of rubber vulcanizates is proposed. The method involves the measurement of oxidative stress decay and the change in sol fraction, which allow us to distinguish whether scission occurs randomly along the main chain, near crosslinks or of crosslinks. The applicability of this method was well established using natural rubber vulcanizates as the reference samples. The chain scission of cis‐1,4‐polyisoprene vulcanizaties was proved to take place randomly along the main chain irrespective of their crosslink structure. On the other hand, the chain scission of dicumyl peroxide cured cis‐1,4‐polybutadiene takes place selectively near crosslinks. It is suggested that the unusual behavior of cis‐1,4‐polybutadiene vulcanizates is due to the characteristic structure of the crosslinks.
Four‐center‐type photopolymerization in the crystalline state. IX. Characteristic features of topochemical process and polymer properties thus obtained
Authors: Hasegawa Masaki , Nakanishi Hachiro , Yurugi Tadashi
Published: April 2003

Changes in TG‐DSC diagrams and X‐ray diffraction patterns in the course of four‐center‐type photopolymerization of 2,5‐distyrylpyrazine (DSP) and thermal depolymerization of poly‐DSP were investigated. It has been found that as‐polymerized poly‐DSP crystal with high molecular weight does not melt but depolymerizes into the oligomer in the crystalline state. The crystal change found in the depolymerization was just the reverse of that in the polymerization. From the results a reversible topochemical process, which comprises monomer lattice‐controlled photopolymerization and polymer lattice‐controlled thermal depolymerization, has been established between DSP and poly‐DSP. Quantitative thermal analysis reveals that both of the two endotherms of poly‐DSP crystal include the heat of crystallization as well as that of depolymerization. Several specific properties of a topochemical product of as‐polymerized poly‐DSP crystal, such as nonreproducibility of the original crystal structure by recrystallization and superior stabilities to thermal depolymerization and photooxidation, are discussed in comparison with natural cellulose.
Aromatic polyamides. II. Synthesis, wet‐spinning, and fiber thermal characterization of poly(4,4′‐oxanilideterephthalamide) and copolymers with 4,4′‐oxydianiline or isophthalic acid
Authors: Silver Frank M. , Dobinson Frank
Published: April 2003

Poly(4,4′‐oxanilideterephthalamide) (coded A‐202) was prepared from 4,4′‐diaminooxanilide (DAO) and terephthaloyl chloride (TCI) in N,N‐dimethylacetamide (DMAc)/5% LiCl and DMAc (5% LiCl)/hexamethylphosphorictriamide (HMPA) solvents. Fiber with tenacity/elongation/modulus at 1% extension (t/e/m) of 5.2 grams per denier (gpd)/1.9%/316 gpd was obtained. The all‐para A‐202 tended to precipitate from solution. More soluble copolyamides were prepared from DAO and TCl in combination with either 4,4′‐oxydianiline (A‐202/ODA) or isophthaloyl chloride (A‐202/I) in DMAc (5%LiCl). A‐202/ODA solutions were spun to fiber with t/e/m of 11.2 gpd/6%/217 gpd; A‐202/I gave fiber with t/e/m of 6.4 gpd/1.3%/432 gpd. Dynamic mechanical analyses (Vibron) and dilatometric measurements of A‐202, A‐202/ODA, and A‐202/I showed no glass transition temperature below 200°C. Differential thermal analyses (DTA) revealed no transitions below 400°C. Thermogravimetric analyses (TGA) at 15°C/min exhibited substantially no weight loss in air at temperatures up to 400°C.
Study of kinetic regularities and mechanism of methyl methacrylate radical polymerization in the presence of orthophosphoric acid
Authors: Garina E. S. , Olenin A. V. , Zubov V. P. , Kuchanov S. I. , Povolotskaya E. S. , Kabanov V. A.
Published: April 2003

Photoinitiated homophase polymerization of methyl methacrylate (MMA) at 25°C in the presence of a complexing agent, orthophosphoric acid (H3PO4), was studied. It was found that in addition to the increase in initial polymerization rates and molecular weights of PMMA the system MMA/H3PO4 reveals postpolymerization that does not retard with time and is accompanied by an increase on average molecular weight. Macroradicals, lifetimes of which grow considerably in the presence of the complexing agent, are shown to be responsible for the termination‐free postpolymerization in this system by the living chain mechanism. The effect of various factors on the kinetics of postillumination polymerization was studied. A drastic decrease in the rate of bimolecular termination of poly(methyl methacrylate) radicals was shown to be related to the change in conformational properties and to the association of propagation chains via complexing with H3PO4. The mechanism of polymerization in this system was discussed.
Poly(β‐amino acid)s. IV. Synthesis and conformational properties of poly(α‐isobutyl‐L‐aspartate)
Authors: Yuki Heimei , Okamoto Yoshio , Taketani Yutaka , Tsubota Tetsuo , Marubayashi Yoshizo
Published: April 2003

Poly(α‐isobutyl‐L‐aspartate) was prepared by the polycondensation reaction of p‐nitrophenyl ester of α‐isobutyl‐L‐aspartate and the conformation of the poly(β‐amino acid) was investigated by X‐ray diffraction, polarized infrared, circular dichroism (CD), optical rotatory dispersion (ORD), and NMR spectroscopy. α‐Isobutyl β‐p‐nitrophenyl‐L‐aspartate hydrochloride and hydrobromide were used as monomers and dimethylformamide, chloroform, and chlorobenzene, as solvents. A high‐molecular‐weight polymer with [η] 1.0 dl/g (dichloroacetic acid, 25°C) was formed in the polymerization of the hydrochloride in chloroform at 25°C. The X‐ray diagram and polarized infrared spectrum of the stretched polymer film obtained from a chloroform solution suggested a cross‐β‐form as the most probable structure in the solid state. The CD spectra of the polymer in a 2,2,2‐trifluoroethanol (TFE) solution and its film cast from the solution showed a peak at 205 nm and a trough at 190 nm which were assigned to a β‐structure. The polymer was associated in chloroform. The NMR and ORD spectra in chloroform were similar to those in TFE, which suggests that the polymer also exists in the β‐structure in chloroform. The addition of small amounts of dichloroacetic acid and sulfuric acid to chloroform and TFE solutions, respectively, destroyed the β‐structure. A random copolymer of α‐isobutyl‐L‐aspartate with β‐alanine was also prepared by polycondensation reaction. The copolymer apparently did not form an ordered structure in the solid state or in solution.
Equilibrium cyclotrimerization of ether oxygen‐substituted aliphatic aldehydes
Authors: Hashimoto Kazuhiko , Sumitomo Hiroshi , Kawase Sanshiro
Published: April 2003

This article describes the equilibrium cyclotrimerization of β‐methoxypropionaldehyde (MPA), 4,7‐dioxaoctanal (DOA), and n‐octanal (OA) initiated by boron trifluoride etherate in toluene at a temperature range of −10 to 25°C. The enthalpy and entropy changes corresponding to the conversion of 1 mole of the monomers to 1/3 mole of their cyclic trimers in toluene solution, at the initial monomer concentration of 1 mole/liter, were evaluated as follows: ΔHss = −5.9 ± 0.3 kcal/mole and ΔSss = −19.1 ± 1.3 cal/mole deg for the MPA system; ΔHss = −7.4 ± 0.4 kcal/mole and ΔSss = −24.1 ± 1.7 cal/mole deg for the DOA system; ΔHss = −6.1 ± 0.4 kcal/mole and ΔSss = −21.2 ± 1.5 cal/mole deg for the OA system. The comparison of these values with those in their polymerization indicates that the cyclotrimerization of aldehydes is thermodynamically of greater advantage than their polymerization. The effects of long and polar substituents are discussed from the view‐point of the intermolecular interactions by the polar groups in monomers and their cyclic trimers.
Hydrogen chain transfer in olefin polymerization with organometallic catalysts
Authors: Mortimer George A. , Ort Morris R. , Mottus Edward H.
Published: April 2003

Hydrogen has been shown to be a true chain‐transfer agent with some organometallic olefin polymerization catalysts. However, the Mayo equation for chain transfer in free‐radical polymerization does not fit quantitative data from organometallic catalysts. There appear to be two reasons for the lack of fit. First, the Mayo equation considers the competition between hydrogen and olefin for the growing chain but does not account for their competitive absorption on the catalyst (coordination with vacant orbitals on the transition metal). Second, some organometallic catalysts gradually absorb hydrogen irreversibly to give a new catalyst species of altered behavior.
Photodegradation of aramids. I. Irradiation in the absence of oxygen
Authors: Carlsson D. J. , Gan L. H. , Wiles D. M.
Published: April 2003

The photolysis reactions of a series of isomeric fully aromatic polyamides (aramids) have been investigated in the absence of oxygen by ultraviolet and luminescence spectroscopy. Several of the aramids were found to undergo photo‐Fries rearrangements to give 2‐aminobenzophenone backbone units when irradiated either as films, fibers, or dissolved in liquids. Quantum yields for this rearrangement were low, < 1 × 10−6 mole/einstein, and increased with decreasing aramid glass transition temperature and increasing backbone mobility. The formation of gel, carbon monoxide, and a strong ESR signal were consistent with a free‐radical mechanism for the rearrangement.
Urea‐formaldehyde resins. III. Constitutional characterization by 13C fourier transform NMR spectroscopy
Authors: Tomita Bunichiro , Hatono Shiro
Published: April 2003

13C Fourier transform NMR has been used to characterize a random chemical structure of ureaformaldehyde resins. By comparison of 13C chemical shifts with synthesized standard derivatives from urea and formaldehyde the analysis of reacted formaldehyde was completed. In a 13C spectrum of resin each signal due to reacted formaldehyde (e.g., methylol group, methylene group, and dimethylene ether group) was isolated.

Measurement of a 13C spectrum of resin by the gated decoupling of proton without nuclear Overhauser effect made a quantitative analysis of reacted formaldehyde possible. In this quantitative analysis a 13C quantity of carbonyl groups in urea residue can be directly compared with that of each combined formaldehyde.
Distribution of polymer deposition in plasma polymerization. III. Effect of discharge power
Authors: Yasuda H. , Hirotsu T.
Published: April 2003

Distribution of polymer deposition in an inductively coupled rf discharge system is studied as a function of level of discharge power with acetylene and styrene as monomers. When a fixed flow rate is used, the discharge power has a relatively small effect on the pattern of distribution of polymer deposition as long as values of W/FM, where W is discharge wattage, F is flow rate, and M is molecular weight of monomer, are maintained above a critical level to maintain full glow in the reaction tube. It has been shown that plasma polymerization of two monomers which have different molecular weights can be compared in a fair manner by selecting conditions to yield similar value of W/FM.
Radiation effect on polystyrene deposited and grafted on silica gel
Authors: Kusama Yasuo , Udagawa Akira , Takehisa Masaaki
Published: April 2003

The effect of radiation on polystyrene was studied in the presence and absence of silica gel by molecular weight measurement with GPC. Polystyrene crosslinked under vacuum in the absence of silica gel, but it either crosslinked or degraded by radiation, depending on the molecular weight of the polymer in the presence of silica gel. Part of the deposited polymer bonded to silica gel by radiation; the G value for graft‐chain formation is in the range of 0.01–0.1. Irradiation of polystyrene grafted on silica gel resulted in degradation of the graft chain because of the transfer of energy from silica gel. The G value for main chain scission was about 2 when graft polymer was irradiated in the absence of homopolymer. The degradation of graft polymer was suppressed when the polymer was irradiated in the presence of homopolymer, and the amount of unextractable polymer from silica gel increased with increasing irradiation. This adds evidence to the estimation that an increase in grafting percent coupled with a slight decrease in molecular weight at a later stage of radiation‐induced polymerization of styrene adsorbed on silica gel is due to a secondary effect of radiation on the polymer.
Quasi‐equilibrium states of copolymers that simultaneously crystallize and interchange structural units
Authors: Theil Michael H.
Published: April 2003

A quasi‐equilibrium model of a step‐growth copolymer that crystallizes and interchanges structural units simultaneously is presented. Equilibrium values of counit‐sequence‐length distribution in the amorphous phase and degree of crystallinity are calculated in a system for which crystallite thickness is determined by nucleation. When applied to calculations, the model predicts that the counits of the amorphous phase will tend to be ordered in blocks. The crystalline content of the whole polymer and the extent of ordering counits along the chain decreases with increasing temperature. The model predicts temperature ranges for some whole copolymers in which one of two similarly stable, disparate combinations of crystallinity and sequence‐length distribution may prevail.
Functionality and structure of polymers. II. Photodimerization of polymer‐bound anthryl groups and thermal dissociation of the photodimers
Authors: Tazuke Shigeo , Hayashi Naoya
Published: April 2003

Anthryl groups bound to various polyesters and polyesterurethanes as side groups were photodimerized in solid state in a nitrogen atmosphere. The rate of photodimerization is strongly affected by polymer structure as observed in the photodimerization of dilute solutions. The results revealed the importance of segment mobility rather than local concentration of anthryl groups. Temperature effects on the rate of photodimerization indicated that the rate jumped above the glass transition temperature (Tg). A definite difference in photodimerization behavior was apparent between polyesters and polyesterurethanes. Anthryl groups in polyesters were to some extent photodimerized at Tg, whereas polyesterurethanes did not react at all. Hydrogen bonding in polyesterurethanes restricted the movement of anthryl groups and consequently additional energy was required to liberate them and allow photodimerization to proceed. The anthryl groups can be recovered from the photodimerized polymers by heating to 80–100°C. The activation energy of thermal dissociation of the photodimer depends to a great extent on polymer structure. These results were interpreted as being due to the strain brought about by photodimer formation exhibited this dependence. The photodimerization–thermal dissociation cycle was reversible (reversibility: 95–100% under nitrogen). A novel principle of reversible photomemory, based on dry unit processes that consisted of image recording above Tg, fixation of image by cooling below Tg, and image erasure at elevated temperature, was proposed.
Radical‐cationic photoinitiated copolymerization of isobutylene with isoprene in the presence of vanadium (IV) chloride
Authors: Toman Luděk , Pilař Jan , Spěváček Jiří , Marek Miroslav
Published: April 2003

EPR spectra of isoprene and isobutylene‐isoprene mixture has been studied in the presence of VCl4 in dark and under irradiation, respectively. Analogously, as with isobutylene, a radical‐cation of isoprene is formed under irradiation, and in a mixture of both monomers radical‐cations of isobutylene and isoprene are formed side by side. Formation of the isoprene radical‐cation prevails even in an excess of isobutylene, that is, in an isobutylene‐isoprene ratio of 8:1. Peroxy radicals which inhibit the photochemical copolymerization of isobutylene with isoprene were recorded in the presence of oxygen in isoprene and in the isobutylene‐isoprene mixture. The copolymers of isobutylene with isoprene prepared photochemically (unsaturation 1.5–2 mole %) at −30 to −78°C had a considerably higher viscometric molecular weight than copolymer samples prepared under the same conditions with AlCl3 or BF3 catalysts. According to NMR measurements of butyl rubber samples prepared by photochemical copolymerization, all isoprene is incorporated in the polymer chain as 1,4‐structural units.
Adsorptionsmodifizierung der oberfläche von mineralischen polymerfüllstoffen als die methode deren aktivierung
Authors: Tolstaja S. N. , Taubman A. B. , Mikhailova S. S.
Published: April 2003

The process of modifying the surface of particles of dispersed polymer fillers, using tensides, has been studied. The main principles were established with regard to the effect of modification of titanium dioxide and kaolin on the structure formation in solutions and block formations of chlorinated poly(vinyl chloride) resin and rubber, depending on the nature and concentration of the modifier. The decisive part played by chemisorption of the tenside in lyophilization (water‐repellency treatment) of the surface of the filler and its activation, as a structure former, has been elucidated.