bluuebunny/crossref_metadata_2025_split huggingface dataset:
Detection of “memory” effects in polyethylene by magnetic susceptibility
Authors: Phaovibul O. , Loboda‐Čačković J. , Hosemann R. , Baltà‐Calleja F. J. 
Published: April 2003

AbstractThe relevance of diamagnetic susceptibility as a tool for the structure analysis of solid high polymers is stressed in the light of some new examples. The present results complement previous data and offer new aspects on the diamagnetic investigations of longchain hydrocarbons, especially polyethylene (PE). The molecular susceptibility is proportional to the average number of repeat units in the chain. The proportionality factor defines an intermolecular constant μk which characterizes different physical states. This was found to be 2.5 × 10−6 for the liquid and 3.5 × 10−6 cgs for the crystalline state of paraffins and polyethylene (solution‐crystallized). For melt‐crystallized material, μk, approaches the typical value of the liquid paraffin in agreement with previous results. Such a low μk is probably related to the increased disorder of the paracrystalline lattice domains, in contrast to the more ordered microparacrystallites in the so‐called “single crystals,” where μk = 3.5 × 10−6. In single crystals of branched PE, μk approaches 2.5 × 10−6 with increasing branching ratio. Like paraffins in the gaseous state, molten PE, with chains longer than 1000 Å, has μk = 0. If the solution‐crystallized material is molten for 10 min and thereafter cooled, μk retains the original value 3.5 × 10−6 cgs characteristic of the crystalline state. Hence, solution‐crystallized polyethylene apparently possesses a kind of “memory.” Such a “memory” can, nevertheless, be partly destroyed when molten PE is stirred for 10 min and then quenched. Aggregates of solution‐precipitated crystals with 3% branching concentration give μk = 2.9 ± 0.2 × 10−6 in good agreement with x‐ray diffraction data. Finally, experimental details on the magnetic measurements are critically discussed, and various aspects of improvements for further investigations are also described.
ESR study of structural changes in high‐density polyethylene subjected to cyclic tensile stress
Authors: Nagamura Toshihiko , Kusumoto Naoshi , Takayanagi Motowo 
Published: April 2003

AbstractBulk‐crystallized high‐density polyethylene is subjected to cyclic tensile stress and then irradiated by γ‐rays to “spin‐label” polymer molecules. The change of crystalline texture in the fatigue process before initiation of necking is detected by the ESR method. The line‐resolution parameter of the ESR spectrum, which reflects the degree of regularity of molecular arrangement, first decreases, then increases somewhat, and finally becomes almost constant during fatigue cycling. The concentration of radicals trapped in a fatigued sample is larger than that in the unfatigued one. The excess radicals disappear during heating by a process of low activation energy in the temperature region of the mechanical γ dispersion. The degree of crystallinity evaluated from x‐ray diffraction and density scarcely changed during fatigue cycling. The size of the mosaic block crystals estimated from the radical trapping capacity showed a rapid decrease at the initial stage of fatigue. The x‐ray paracrystalline analysis indicates a similar but not so drastic decrease. These results lead to the conclusion that the slight disordering of crystalline texture accompanying the decomposition of mosaic block crystals in the lamellae occurs at the initial stage of the fatigue process, following which crystals reform somewhat and then remain unchanged until the initiation of necking.
Crystal structure of poly‐p‐xylylene. I. The α form
Authors: Iwamoto Reikichi , Wunderlich Bernhard 
Published: April 2003

AbstractThe molecular conformation and the crystal structure of α‐form poly‐p‐xylylene has been determined by x‐ray diffraction. The polymer has a monoclinic unit cell with a = 5.92, b = 10.64, c (fiber axis) = 6.55 Å, and β = 134.7°. Two chains pass through the unit cell, and the space groups is C2/m. The packing fraction is 0.705. One monomer unit makes up the fiber identity period and the internal rotation angles are 0° and 90° for the CH2CH2 and CH2ϕ bonds, respectively. All benzene rings are in parallel orientation, perpendicular to the ac plane.
Slow motion of long‐chain molecules in solution with internal correlations
Authors: Caroli B. , Saint‐James D. , Jannink G. 
Published: April 2003

AbstractThe Rouse equations for the dissipative motion of long‐chain molecules are reformulated in terms of coupled Langevin equations. While in the conventional Rouse model the random forces acting on each bead are supposed to be uncorrelated, the calculation given here admits of any correlation between the forces. By virtue of the second fluctuation dissipation theorem this corresponds to an added friction factor, called the “internal viscosity” in agreement with earlier work of Kuhn and Kuhn, Cerf, and of Peterlin. In the mode decomposition, this added friction factor happens to be an even function of the mode frequency. From this general model it is possible to compute formally the mean‐square displacement function. It takes a simple form if one assumes that forces are correlated only on adjacent beads and that their correlation functions are δ functions. The results of the calculation are best displayed in the Fourier transform of the meansquare displacement, which is directly related to the neutron incoherent scattering cross section. It is seen that the presence of internal viscosity modifies the behavior of the chain for a time scale of the order of the relaxation time of the elementary segment.
Decay of catalytic activity during the cationic polymerization of capryllactam
Authors: Puffr R. , Šebenda J. 
Published: April 2003

AbstractAt lower concentrations of initiator and temperatures above 200°C, the polymerization of capryllactam initiated by hydrogen chloride is characterized by two kinetically different stages: the initial rapid growth becomes considerably slower due to the fast transformation of the original growth centers into amidines. The steep decrease in molecular weight during hydrazinolysis indicates that the amidine groups are also present inside polymer molecules. The formation of these structures may be explained by condensation of the amino endgroups with the amide or acyllactam groups.
Stereochemistry of alternating methacryloyl‐L‐valine methyl ester–maleic anhydride copolymer
Authors: Nishihara Koji , Sakota Naokazu 
Published: April 2003

AbstractThe stereochemical composition of an alternating methacryloyl‐L‐valine methyl estermaleic anhydride (L‐MAVM/MAn) copolymer which was prepared by the photocopolymerization of L‐MAVM and MAn in dioxane at 25°C without initiator was investigated by proton magnetic resonance spectroscopy. The resonance of the ester methyl protons of the L‐MAVM unit appeared as three split peaks at 3.65, 3.76, and 3.82 ppm, which could be assigned to those of the coisotactic (di‐threo‐tri‐isotactic), coheterotactic and cosyndiotactic triads, respectively. The triad cotacticity determined according to these assignments indicated that the copolymer was composed predominantly of di‐threo‐tri‐isotactic triad. Similarly PMR spectroscopic investigation of the acryloyl‐L‐valine methyl ester–maleic anhydride (L‐AVM/MAn) copolymer with a 1:1 molar ratio of the monomers showed that the main tactic fraction of the copolymer was also di‐threo‐tri‐isotactic one. Nevertheless, the circular dichroic investigation of the L‐AVM/MAn copolymer before and after hydrolysis denied asymmetric induction into the polymer main chain. These results suggest that the propagation step in the photocopolymerization of L‐MAVM or L‐AVM with MAn proceeds by the trans‐trans opening of the complexmer composed of a 1:1 molar ratio of L‐MAVM or L‐AVM and MAn.
An application of spin trapping to radical polymerizations
Authors: Kunitake Toyoki , Murakami Shigeru 
Published: April 2003

AbstractRadical polymerizations and copolymerizations were carried out in the presence of phenyl tert‐butyl nitrone(PBN) and tert‐nitrosobutane (t‐BuNO), and the structure of the spin adduct formed was investigated by ESR spectroscopy. PBN adducts gave the same ESR pattern, and the variation of the splitting constant was not large enough to warrant its use for the structure assignment. Therefore, the subsequent trapping experiments were performed with t‐BuNO. The polymerization mixture of representative monomers showed esr patterns that are indicative of the propagating radical being trapped. These trapped radicals were not necessarily very stable and, in most cases, disappeared after long reaction periods. In the case of α‐methyl substituted monomers, additional nine‐line spectra were observed which were attributed to trapping of the radical species formed by hydrogen abstraction from the α‐methyl group. The tert‐butyl radical which was formed by decomposition of t‐BuNo was probably responsible for the hydrogen abstraction. In the case of styrene, methyl acrylate, and methyl methacrylate, characteristic ESR patterns of the propagating radicals were observed with polymers which were prepared in the presence of t‐BuNO and purified by reprecipitation. Simultaneous trapping of different propagating radicals was attempted in several copolymerization systems. However, this was generally unsuccessful, because of the large difference in reactivities of the propagating radical with t‐BuNo.
Some aspects of graft polymerization of vinyl monomers onto cellulose by use of tetravalent cerium. IV
Authors: Mansour Olfat Y. , Nagaty Ahmed 
Published: April 2003

AbstractIntense agitation markedly decreased the homopolymer formation in homopolymerization reactions. Graft polymerization is similarly influenced, the main effect being on the propagation process. The results achieved in this work indicate that in grafting reactions, growing polymer radicals are produced mainly through the transfer of radicals formed at the cellulose backbone to the monomer where propagation takes place. The growing polymer radicals either recombine with active sites on the cellulose leading to grafting or react with each other through coupling and/or are oxidized with ceric ions to give homopolymer.
New imidazoisoquinoline ladder polymers
Authors: Sicree A. J. , Arnold F. E. , Van Deusen R. L. 
Published: April 2003

AbstractIn previous studies on poly{(7‐oxo‐7, 10H‐benz[de]imidazo[4′,5′:5,6]‐benzimidazo‐[2,1‐a]isoquinoline‐3,4:10,11‐tetrayl)‐10‐carbonyl} it was observed that the polymer exhibits very unusual film‐forming properties. The ladder polymer forms supermolecular aggregates in solution which translates to a high degree of interchain packing in the bulk. New ladder imidazoisoquinoline polymers have been prepared in an effort to relate the variance of molecular structure to the aggregation behavior of this class of polymers. The polymers were prepared from the solution polycondensation of 1,4,5,8‐naphthalene tetracarboxylic acid or dianhydride with 1,2,5,6‐tetraaminonaphthalene, 2,3,7,8‐tetraaminophenazine and 2,3,7,8‐tetraaminodibenzofuran. It was found that the extent of interchain packing in the bulk is dependent to a large degree on the molecular geometry of the polymer backbone.
Studies on the photooxidation mechanism of polymers. I. Photolysis and photooxidation of polystyrene
Authors: Rabek Jan F. , Rånby Bengt 
Published: April 2003

AbstractA new mechanism has been proposed for the photooxidation of polystyrene as film and in benzene. The initial stage of the photooxidative degradation may involve reactions of singlet oxygen with polystyrene molecules. Singlet oxygen may be formed in the reaction between excited benzene ring in polystyrene molecule and molecular oxygen. The addition of singlet oxygen quenchers such as 1,3‐cyclohexadiene or β‐carotene reduces the rate of polymer degradation in benzene solution. The mechanisms of the photolysis of polystyrene as film and in benzene solution, in vacuo and in the presence of oxygen, are discussed and interpretations proposed. The pronounced yellowing of polystyrene during the photooxidation process is interpreted as a reaction involving benzene ring‐opening photooxidation in polystyrene molecule. These results were obtained by comparing ultraviolet and infrared spectra in experiments of photooxidation of pure liquid benzene and polystyrene film.
Radiation‐induced emulsion polymerization of ethylene. IV. Effect of pressure, temperature, and additives on rate in connection with number of polymer particles
Authors: Senrui Shiro , Takehisa Masaaki 
Published: April 2003

AbstractThe effects of pressure, temperature, and additives on the rate of radiation‐induced emulsion polymerization of ethylene with FC‐143 as emulsifier were studied kinetically. The rate of polymerization was proportional to the 2.5 power of ethylene fugacity, and the apparent rate constant (rate of polymerization/2.5 power of ethylene fugacity) was constant below 78°C. Above this temperature, the rate constant decreased with an apparent activation energy of −8.2 kcal/mole. These facts can be interpreted in connection with the polymer structure and the change of rate of escape of radicals from the polymer structure and the change of rate of escape of radicals from the polymer particle into the aqueous phase. The rate of polymerization decreased on addition of a series of n‐aliphatic alcohols due to the chain‐transfer reaction and consequent escape of radicals to the aqueous phase. On the other hand, the addition of tert‐butyl alcohol increased the rate of polymerization, probably because of its effect in increasing swelling of the polymer particles. Addition of electrolytes increased the rate of polymeriaztion as a result of the increase of the number of polymer particles.
Crosslinked polymers of styrene with 1,3,5‐triisopropenylbenzene
Authors: Furlani A. , Bicev P. , Fiorentino M. 
Published: April 2003

AbstractCrosslinked polymers of improved properties compared to those of pure polystyrene, are obtained by the thermal or radical copolymerization of styrene with 1,3,5‐triisopropenylbenzene. The copolymers are transparent glassy solids, practically insoluble in most organic solvents and easily machineable. They decompose at about 350°C. Copolymers containing 5–30% of 1,3,5‐triisopropenylbenzene exhibit the better properties.
Radiation‐induced emulsion polymerization of ethylene. V. Copolymerization of ethylene with hexafluoropropylene
Authors: Senrui Shiro , Ito Masayuki , Takehisa Masaaki 
Published: April 2003

AbstractThe emulsion copolymerization of ethylene with hexafluoropropylene was studied by using 60Co γ‐radiation as the initiator. The apparent rate of copolymerization is proportional to the 1.6 power of ethylene fugacity. The activation volume was calculated from the pressure dependence of the apparent rate constant of copolymerization and was −30 ml/mole, which is smaller than the value reported by Wada et al. for ethylene polymerization in tert‐butyl alcohol. The copolymer produced had a broad composition from ethylene‐rich to alternative. As expected, the former was a crystalline, polyethylenelike copolymer, but the latter was an amorphous and rubberlike copolymer. The glass transition temperature of the copolymers increased with an increase in hexafluoropropylene content. The thermal degradation temperature in an atmosphere of nitrogen decreased slightly with introduction of hexafluoropropylene in polyethylene, but the thermal degradation behavior in air was complicated by the introduction of hexafluoropropylene.
Synthesis and some properties of poly‐(2,5‐trimethylene benzimidazole) and poly‐(2,5‐trimethylene benzimidazole hydrochloride)
Authors: Aharoni Shaul M. , Litt Morton H. 
Published: April 2003

AbstractA polymer, poly(2,5‐trimethylene benzimidazole), the first of a new family of nonsymmetrical polymers, was synthesized via an eight‐step synthetic route. The polymer, obtained by melt polymerization, is amorphous and in its neutral form behaves as a moderate insulator. It forms 1 : 1 HCl adducts. When cast from formic acid solution, it forms 1 : 1 formic acid adducts. The acid adducts are semiconductors with resistivities in the 106–108 ohm‐cm range. Space‐charge effects are generated in the adducts as carrier mobility rises.
Thermoxidative degradation leading to gel in poly(ethylene terephthalate)
Authors: Spanninger Philip A. 
Published: April 2003

AbstractPoly(ethylene terephthalate) oxidizes on heating at 300°C in an air stream. Various literature has cited crosslinking under such conditions through a butanetriol or a biphenyltricarboxylic acid. In this study gelled polymer was found to contain the latter trifunctional compound, but not the former. In addition, 4,4′‐biphenyldicarboxylic acid was found in the degraded gel. There is further indication for the presence of other multifunctional species. All components are consistent with general free‐radical arylation mechanisms.
Synthesis and thermal properties of a new class of high‐temperature polyamides from hexahydrobenzodipyrrole
Authors: Doddi Namassivaya 
Published: April 2003

AbstractA series of polyamides was synthesized by the interfacial polycondensation of 1,2,3,5,6,7‐hexahydrobenzo [1,2‐c:4,5‐c′] dipyrrole with isophthalic, terephthalic, oxydibenzoic, sebacic and adipic acid chlorides. High molecular weight polymers with inherent viscosities ranging from 0.4 to 2.3 dl/g were obtained. Polymerization with isophthaloyl chloride gave the highest molecular weight polymer in this series. These polyamides melt between 350°C and 475°C, depending on structural differences as determined by differential scanning calorimetry (DSC). Rapid weight loss in these polymers was observed in the range of 350–400°C under thermogravimetric analysis in a nitrogen atmosphere. All these polyamides are susceptible to photooxidative degradation. The results were compared with Nomex polymer poly(1,3‐phenylene isophthalamide).
Chain transfer studies of alternating copolymerization
Authors: Funt B. Lionel , Rhodes Heather E. W. 
Published: April 2003

AbstractDimethylaniline (DMA) induces chain transfer in the zinc bromide‐complexed donor–acceptor polymerizations of styrene–acrylonitrile to form alternating copolymers. The Mayo plots are linear, but the rates decrease with increase in DMA and degradative chain transfer occurs. Although conventional free‐radical transfer agents have negligible effect on the rates or molecular weights, a twentyfold reduction of molecular weight is obtained with DMA. Spectroscopic data indicate the formation of an equimolar complex of DMA and ZnBr2, but the lowering of molecular weight is not attributable to the reduction of the effective ZnBr2, concentration. A possible mechanism involving a competition between [ZnBr2(DMA)2] and [ZnBr2,DMA,AN] is suggested.
Influence of covalently bonded dyes on the photooxidative destruction of poly(vinyl alcohol)
Authors: Kalontarov I. Ya. , Kostina N. V. , Kiseleva N. N. 
Published: April 2003

AbstractThe influence of the dye and type of polymer bond on the rate of photo‐oxidation in poly(vinyl alcohol) (PVA) films was investigated. C. I. Reactive Yellow 4 and C. I. Reactive Blue 4 dyes and their inactive forms were used as ultraviolet light absorbers. It was shown that in the case of PVA samples dyed with these dyes, the processes of structurizing due to the secondary reactions take place, as it can be supposed on the basis of the changes in the radical concentration yield and growth of intrinsic viscosity. The kinetics of PVA photo‐oxidative destruction was investigated by ESR and infrared spectroscopy methods. The loss of strength under photodestruction was checked viscometrically.
Polyamine polymers from active hydrogen compounds, formaldehyde, and amines
Authors: Tomono Tsugikazu , Hasegawa Etsuo , Tsuchida Eishun 
Published: April 2003

AbstractActive hydrogen compounds such as hydroquinone (HQ), cyclohexanone (CH), acetophenone (AP), and 4,4′‐methylene bis‐N‐methylaniline (MNA) polymerized with formaldehyde (F) and secondary diamines to produce Mannich base polyamine polymers. The HQ‐containing polymers were oxidized to benzoquinone (BQ)‐containing polymers and their redox properties were investigated in the desulfurization of hydrogen sulfide.
Applications of ESCA to polymer chemistry. IV. The composition and structure of copolymers of ethylene with tetrafluoroethylene
Authors: Clark D. T. , Feast W. J. , Ritchie I. , Musgrave W. K. R. , Modena M. , Ragazzini M. 
Published: April 2003

AbstractMolecular core binding energies have been measured by ESCA for a series of copolymers of tetrafluoroethylene and ethylene. Detailed analysis of the results demonstrates the utility of ESCA for determination of copolymer compositions and for providing information on important structural features for these copolymers.
Anionic polymerization of a series of five‐membered cyclocarbosiloxanes
Authors: Suryanarayanan B. , Peace B. W. , Mayhan K. G. 
Published: April 2003

AbstractA study was conducted of the anionic polymerization of a series of methyl‐ and/or phenyl‐substituted five‐membered cyclocarbosiloxanes. The polymerization was initiated by lithium n‐butyldiphenylsilanolate in the presence of tetrahydrofuran. The rate of conversion of monomer to polymer was measured in an NMR spectrometer. The rate of polymerization was largely dependent upon the structure of the growing chain ends. The apparent activation energies were in the range 10–14 kcal/mole for the series.
Photoreversible reactions of poly(vinyl cinnamylideneacetate) and its model compound
Authors: Tanaka Hideaki , Otomegawa Eiich 
Published: April 2003

AbstractPhotochemical reactions of poly(vinyl cinnamylideneacetate) and its model compound were studied. The irradiation of these compounds with light of wavelength longer than 300 nm produced dimeric forms of cinnamylideneacetyl groups, which were effectively dissociated into the monomeric forms by the irradiation with 254 nm light.
Some applications of gel‐permeation chromatography in investigations of structure and the solution properties of radical‐initiated poly(vinyl chloride)
Authors: Kolínský M. , Janča J. 
Published: April 2003

AbstractThe applicability of the published universal calibration parameters for gel‐permeation chromatography on polystyrene standards and poly(vinyl chloride) samples with a defined structure has been compared. It was shown experimentally that of several theoretically possible molecular weight averages attributed to the elution volume at the position of the peak maximum, the root mean‐square average molecular weight MRms = (MwMn)0.5 shows the best accordance. The molecular weights obtained by gel‐permeation chromatography were compared with those determined by viscometry, osmometry, and the light‐scattering method. The reproducibility of gel‐permeation chromatography measurements is 3%, and the average variance of the results as compared with results obtained by the above methods is about 8%. It was also found that the gel‐permeation chromatography does not involve any anomalies interfering with results obtained by other methods.
An electrochemical route to phenol–formaldehyde precursors
Authors: Phillips D. C. , Meier J. F. , Jackson J. A. 
Published: April 2003

AbstractWith the aid of VPC and NMR, the electroinitiated polymerization of phenol or p‐tert‐butyl phenol with formaldehyde in the presence of basic electrolytes has been investigated over a range of current densities. Results from an electroinitiation study were contrasted with base‐catalyzed thermal polymerizations and, except for yield, found to be essentially invariant. GPC of the electroinitiated and thermally polymerized resins indicates similar results with low molecular weight species of relatively narrow molecular weight distribution being the principal products. An electroinitiation mechanism, in agreement with the mechanism for base‐catalyzed thermal polymerization is proposed to describe these experimental results.