bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of annealing of elongated nylon 6
Authors: Ikeda Susumu , Matsuda Kazuo 
Published: April 2003

AbstractThe shrinkage of extended nylon 6 was studied by the methods of isothermal annealing and tempering. The shrinkage was discussed in comparison with that of amorphous polymer solids in the glass transition region. It was found that the annealing below the melting temperature of crystalline polymer solids showed two effects: one was the shrinkage of samples tracing the quasi‐equilibrium states and the other was the relaxation process stabilizing the strain. The rate of shrinkage of nylon 6 during tempering became large at the two temperature ranges, i. e., one was the glass transition region and the other the neighborhood of elongation temperatures above 100°C. Because of the effect of relaxation stabilizing the strain, the rate of shrinkage during tempering decreased at intermediate temperatures between the two temperature ranges. A stabilizing effect also was found in the fact that γ type crystallites were stabilized during tempering.
A new approach to the theory of rubber elasticity
Authors: Mukherji Barun 
Published: April 2003

AbstractCurrent polymer network theories do not explain the experimental behaviour clearly. The use of Gaussian distribution might be the reason of this limitation. The approximation of the distribution of the chain vector by a Gaussian function implies non‐vanishing probability for chains at full extension and beyond. In the stress‐strain relation, the first derivative with respect to strain of the logarithm of the distribution function is involved. For Gaussian distribution this derivative deviates very much from that of the actual distribution especially at higher extensions. The properties of the said derivatives for different distributions were examined. It is observed that the use of the Langevin distribution might be more realistic. A new approach is suggested on this basis. The tensile force per unit cross section, τ, for an extension ratio α at constant volume has the form

where an average chain contributes a length L in each of the three mutually perpendicular directions and contains n equivalent free links of length l each. The expression contains no unknown parameter. This equation has great similarity with the empirical Mooney‐equation and gives much better agreement with experimental results.
Comments on an estimation of the rigidity of a macromolecular chain from hydrodynamic data by means of graphic methods
Authors: Kovár̂ Josef , Fortelný Ivan , Bohdanecký Miloslav 
Published: April 2003

AbstractIt is demonstrated, by means of an analysis of theoretical relationships, that evaluation of hydrodynamic data by uncritically applied extrapolation methods, especially if the only criterion of their applicability consists in the linearity of graphic plots, may lead to incorrect conclusions about the rigidity of the polymer chain. A simple procedure is suggested for the characterization of the quality of hydrodynamic data from the viewpoint of determination of the rigidity of a polymer chain.
Functional metal‐porphyrazine derivatives and their polymers, 2. Synthesis and properties of polyimides containing metal‐phthalocyanines
Authors: Shirai Hirofusa , Kobayashi Kesayoshi , Takemae Yoshitaka , Suzuki Akira , Hirabaru Okikazu , Hojo Nobumasa 
Published: April 2003

AbstractA novel class of polyimides (14) containing Mt(II)‐phthalocyanine rings has been synthesized by the solution condensation in N‐methyl‐2‐pyrrolidone (NMP) of Mt(II)‐[2,9or10(or2, 16or17)bis(3,4‐dicarboxybenzoyl)]phthalocyanine dianhydride (Mt(II)‐dahPc; Mt(II)=Co(II), Ni(II) and Cu(II); (2–4)) with aromatic diamines such as 4,4′‐methylenebis(aniline), followed by thermal imidization in vacuo at 200°C. The polyamides obtained were soluble in NMP and hexamethylphosphoric triamide, having inherent viscosities up to 0,7 dl·g−1. The polyimides were stable up to 350°C, and showed room temperature‐dc‐resistivities in the range of 1011 to 106 Ω·cm.
Calorimetric studies in the helix‐coil transition of poly(amino acid)s in methanol‐water solvent mixtures
Authors: Baba Yoshihiro , Kagemoto Akihiro , Fujishiro Ryoichi 
Published: April 2003

AbstractBy combining the heat of dilution of solutions of poly(L‐lysine) and poly(L‐ornithine) in methanol‐water solvent mixtures with the corresponding heat of mixing of the methanol‐water system, the integrated heats of the coil‐helix transition of poly(L‐lysine) and poly(L‐ornithine) were estimated to be about −3,1 and −4,4 kJ per mole of the constitutional repeating unit, respectively. The solvent composition at which the transition occurs was determined to be about 0,85 and 0,94 for the volume fraction of methanol for poly(L‐lysine) and poly(L‐ornithine), respectively. These results are in good agreement with those obtained by optical rotatory dispersion.
Relaxation properties of linear polyethers: Dielectric behavior of poly(oxyhexamethylene)
Authors: Riande E. 
Published: April 2003

AbstractThe dielectric relaxation behavior of poly(oxyhexamethylene) was studied over the temperature range 50 to −56°C at different frequencies lying in the interval 102 to 105 Hz. A single absorption and dispersion is observed in the region of −40°C which shows the same frequency temperature location as the α mechanical relaxation. Therefore, it is postulated that the mechanisms that give rise to both the dielectric and mechanical processes are of the same nature. The α relaxation is associated with micro‐Brownian motions in the amorphous phase of the polymer and seems to shift to higher temperature as the number of methylene groups in the repeating unit increases. From the analysis on the flexibility of polyethers, including the limiting case of polyethylene, it is concluded that the lower limit for the glass transition of polyethylene should be in the vicinity of −80°C.
Anionic polymerization of 2‐Oxo‐1,3,2λ5‐dioxaphosphorinane. Thermodynamics
Authors: Kałużyński Krzysztof , Penczek Stanisław 
Published: April 2003

AbstractThermodynamics of the polymerization of 2‐oxo‐1,3,2λ5‐dioxaphosphorinane in bulk initiated by sodium metal is described. Enthalpy (ΔHp = 6,28 ± 0,84 kJ · mol−1) and entropy (ΔS = 19,25 ± 2,51 J · mol−1 · K−1) of polymerization were evaluated from the temperature dependence of the equilibrium nomomer concentration determined directly by 31P{1H} NMR. The results are compared with those obtained previously for the polymerization of other 2‐alkoxy‐2‐oxo‐1,3,2λ5‐dioxaphosphorinanes.
Some observations on complexes of a cobalt phthalocyanine with poly(vinylamine) and their catalytic activity in the autoxidation of thiols
Authors: Schutten Jan H. , Piet Pieter , German Anton L. 
Published: April 2003

AbstractComplexes of the tetrasodium salt of cobalt(II)‐tetrasulfophthalocyanine and poly(vinylamine) were applied as bifunctional catalysts for the autoxidation of thiols to disulfides. Optical and catalytic experiments gave supporting evidence to the hypothesis, that the isolation of cobalt centers and the catalytic activity can be promoted by increasing the relative amount of polymeric base. It appeared that the specific catalytic activity of the polymeric catalysts depends on the number average degree of polymerization (P̄n) of the applied polymer samples. In particular at relatively high cobalt content, samples with comparatively low P̄n give more protection against aggregation of cobalt sites (i.e. inactivation) and, therefore, effect a higher specific catalytic activity. A statistical calculation, suitable to determine the distribution of cobalt sites over the polymeric coils, supports the interpretation of the experimental data.
Time resolved light scattering measurements on the disentanglement diffusion following the degradation of poly(phenyl vinyl ketone)
Authors: Tagawa S. , Schnabel W. 
Published: April 2003

AbstractPoly(phenyl vinyl ketone) was irradiated in 1,4‐dioxane solutions with 25 ns flashes of 347, 1 nm light at various incident intensities. The rate of fragment separation following the very rapid rupture of chemical bonds in the main chains was measured. For this purpose the decrease of the intensity of light scattered by the polymer solution (LSI) was monitored as a function of time after the flash at various scattering angles. It was found that the lifetime of the LSI change τ(LSI) decreased with increasing scattering angle. This is due to the fact that main chain breaks are statistically distributed over all molecules and along the chains thus causing the generation of small and large fragments. The larger fragments which move at smaller speed contribute stronger to the LSI at low scattering angles than the small ones. It was, furthermore, found that τ(LSI) is independent of Zs, the average number of scissions per initial macromolecule, if the fragment size exceeds a critical value which was estimated as being of the order of 103 base units in this case. τ(LSI) decreased with increasing Zs steadily if the average size of fragments was smaller than the critical value. This was evidenced both by measuring τ(LSI) as a function of the initial molecular weight and of the scattering angle. In conclusion: intramolecular interaction is determining disentanglement motions if the chain length exceeds a critical value. At shorter chain lengths pure translational motions become rate determining.
Helical poly(L‐alanine) in trifluoroacetic acid
Authors: Kricheldorf Hans R. 
Published: April 2003

AbstractIn contrast to previous reports of other authors different 1H NMR chemical shifts were found for poly(L‐alanine) and poly(D,L‐alanine) in pure trifluoroacetic acid. The 13C and 15N NMR signals of poly(L‐alanine) are likewise different from those of poly(D,L‐alanine), and they are also different from the signals of the L‐alanine blocks in random copolypeptides such as (Ala/Gly)n, (Ala/Leu)n, (Ala/Val)n, and (Ala/Phe)n. It is concluded that poly(L‐alanine) is helical in trifluoroacetic acid (TFA); however, the optical purity, and thus, the helix stability is dependent on the reaction conditions used for the polymerization of L‐alanine‐NCA. The base initiated polymerization of L‐alanine‐NCA can cause substantial racemization in contrast to the primary amine‐initiated NCA polymerization. Sulfonic acids were found to be better solvents for polypeptides than trifluoroacetic acid, and their addition to TFA solutions of L‐alanine containing polypeptides exerts a strong influence on the chemical shifts and on the optical rotation. However, no clear experimental evidence was found for the helix‐coil transition of poly(L‐alanine) in TFA/sulfonic acid.
Oligomer‐oligomer incompatibility, 2. Oligo(dimethylsiloxane)/oligo(propylene glycol)
Authors: Wolf B. A. , Blaum G. 
Published: April 2003

AbstractThe demixing behavior of 20 representatives of the system oligo(dimethylsiloxane)/oligo(propylene glycol) (ODMS/OPG)The prefix “oligo” has been chosen for all products, since the addition or removal of a few monomeric units changes the physical properties considerably (cf. Tab. I), even in the case of the highest molecular weight sample.
is investigated at pressures up to 1 500 bar. The degrees of oligomerization range from 2 to 5 for the first and from 1 to 57, 6 for the second component. The experimental results are compared with those for the previously studied system oligoisobutene/oligo(propylene glycol) (OIB/OPG). In both cases the observed upper critical temperatures Tc increase with the number of monomeric units of the less polar component, whereas they run through a minimum when the number of monomeric units of the glycol is raised. For the present system the Tc values are found to be considerably higher than that of OIB/OPG and the optimum compatibility can normally be observed already between 1 and 7 propylene glycol units as against 50 in the case of OIB/OPG. In the low pressure region Tc of ODMS/OPG is decreased by pressure for all representatives of this system, while enhanced incompatibility has been found with OIB/OPG. For ODMS/OPG the special features of the critical lines are determined by the chain length of OPG, for OIB/OPG by that of OIB. For ODMS/OPG the initial reduction of Tc by pressure is most pronounced with the highest molecular weight oligo(propylene glycol), for which it amounts up to 0,3 K/bar; with increasing pressure and decreasing chain length the effects become smaller. For the lowest molecular weight sample of OPG the critical lines show a vertex at 700–1000 bar. In any case the two systems under consideration behave in an increasingly similar manner as the pressure is raised. The theoretical evaluation and discussion of the above results is performed by analogy with that of the first paper in this series.
Mechanismus der photopolymerisation des styrols, 4. Zur rolle der photo‐(4π + 2π)‐addukte als kettenüberträger und zur kinetik der photopolymerisation in gegenwart überlagerter, thermischer prozesse
Authors: Kauffmann Harald Friedrich 
Published: April 2003

AbstractThe photopolymerization of styrene was investigated at 25°C, by following the variations in the rate of polymerization and the degree of polymerization with the light intensity, JM, at different wavelengths of the exciting light (λe = 313 nm, λe = 335 nm). The corresponding data were analyzed in terms of the formalism between the rate RP and the viscosity average degree of polymerization Pη. The kinetic evaluation shows that at least at small fractions of the absorbed light and at short duration of the irradiation the stabilization of the growing chain radicals will occur predominantly by bimolecular termination processes and not by chain transfer. This must be attributed to the fact that among the four theoretically possible isomeric photo‐(4π + 2π)‐intermediates (I) 1‐phenyl‐1,2,3,8a‐tetrahydronaphthalene (diastereomers 1a and 1b) and 2‐phenyl‐1,2,3,8a‐tetrahydronaphthalene (diastereomers 1′a and 1′b) the photostationary concentration [1a]∞ of the most reactive chain transfer agent 1a is—as a result of its very small quantum yield of formation (φ1a ≪ φ1b + φ1′a + φ1′b)—extremely low and contributes only a few percent to the total photo‐steady‐state concentration of I. At higher temperatures (T > 25°C) and at small fractions of the absorbed light JM/Jo (λe = 335 nm), the rate of photopolymerization RP is controlled by the contributions of two independent routes of initiation: (1) the rate R, which accounts for the photo‐free radical formation of the photo‐intermediates I, and 2 the rate R, which is derived from the photoinduced free radical generation of the thermally produced Diels‐Alder adducts 1a and 1b. As a further aspect of this analysis the results give strong evidence that the endo adduct 1a, when electronically excited, enters into a very efficient radical forming process, contrary to the other isomers 1b, 1′b, and 1′a, which seem to be mainly deactivated by their individual retro‐Diels‐Alder decompositions and will not enter into free radical formation to any noticeable extent: φS1a ≫ (φS1b + φS1′b + φS1′a) An explanation of the very different stereodynamic behaviour is given.
Synthesis of aromatic polyamides from reactive N, N′‐isophthaloyldi(thiolactam)s and aromatic diamines under mild conditions
Authors: Ueda Mitsuru , Aoyama Shigeto , Imai Yoshio 
Published: April 2003

AbstractSolution condensation polymerization of new reactive diamides, N, N′‐isophthaloyldipyrrolidine‐2‐thione (1a) and N, N′‐isophthaloyldiperhydroazepine‐2‐thione (1b), with aromatic diamines 2 in 1‐methyl‐2‐pyrrolidone at room temperature or above leads to polyamides 3 with moderate molecular weights. The ease of aminolysis of these diamides is discussed in relation to the good leaving nature of the thiolactam moieties and an intramolecular general base catalysis. The condensation polymerization is strongly catalyzed by 1‐hydroxybenzotriazole giving aromatic polyamides with higher inherent viscosities up to 0,9 dl.g−1.
Hydroxyl‐modified epoxy resins: Some technical and analytical aspects
Authors: Dobinson B. , Green G. E. , Hinton I. G. , Hope P. , Martin R. J. , Stark B. P. , Waterhouse J. S. , Young E. W. 
Published: April 2003

AbstractThe modification of epoxy resins by reactions involving their hydroxyl groups is described. For example, reactions with enol ethers, acrylonitrile, ethyl acetoacetate and certain other carboxylic esters, or triethyl orthoformate, gave products which had reduced reactivities towards various hardeners, and which therefore gave lower peak temperatures on cure and/or longer usable lives. Suitable modification of epoxy resins with various other reagents(certain acid anhydrides, epichlorohydrin, or N‐hydroxymethylacrylamide) introduces additional useful functional groups. The uses of a diisocyanate and of α‐naphthyl isocyanate to modify epoxy resins or their mixtures prior to GPC analysis are also mentioned.
Versuche zur modifizierung von poly(9,10‐anthrylen)
Authors: Hinterhofer Otto 
Published: April 2003

AbstractAttempts were made to obtain fusible or soluble derivatives of poly(9,10‐anthrylene) by incorporation of intermediate links in 9‐ and 10‐position, i.e., by preparing a polyester and a polyanhydride of 9,10‐anthracenedicarboxylic acid as well as a polycarbonate of 9,10‐anthrahydroquinone. The results showed that the preparation of the polyester is very difficult and that its thermal resistance is very low (m.p. 140°C, decomposition). The polyanhydride could be obtained in good yields, but it is insoluble and decomposes at the melting point. The polycarbonate could easily be prepared, but it decomposes in a strongly exothermic reaction at 185°C and forms anthraquinone.
Helix‐coil transition in polypeptides having linear alkyl side‐chain and ester group, and some conformational aspects observed by 13C NMR
Authors: Suzuki Yasuyuki , Inoue Yoshio , Chûjô Riichirô 
Published: April 2003

Abstract13C NMR has been used to study the helix‐coil transition induced in polypeptides by trifluoroacetic acid. An attempt is made to separate the influences of conformational change and direct solvent interaction. For poly(γ‐methyl‐L‐glutamate), interactions between trifluoroacetic acid and the ester group of the side chain occur in the helical region. Poly(L‐norvaline) and poly(L‐norleucine) are in the form of “partially distorted helical conformation”. Conformational change and the interaction between trifluoroacetic acid and the peptide group which accompany the helix‐coil transition, affect the chemical shift difference up to Cδ or Cβ of poly(L‐norvaline) and poly(L‐norleucine), On the contrary, in the case of polyglutamates and polyaspartate, these effects are minor for the carbons in the ester portion. The chemical shift differences of these polypeptides can be well interpreted qualitatively by the results for some butyrates, poly(L‐norvaline), and poly(L‐norleucine).
Induced 13C shifts by coil‐supporting solvents observed in oligopeptides as model compounds of polypeptides
Authors: Suzuki Yasuyuki , Inoue Yoshio , Chûjô Riichirô 
Published: April 2003

AbstractThe origin of the chemical shift differences of carbons in polypeptides which accompany the helix‐coil transition has been investigated by using oligopeptides, benzyloxycarbonyl‐γ‐ethyl‐L‐glutamyl‐diethyl‐L‐glutamate and benzyloxycarbonyl‐di‐(γ‐ethyl‐L‐glutamyl)‐diethyl‐L‐glutamate, as models of the backbone of polypeptides. Structures of aggregates in deuterated chloroform were proposed for these oligopeptides on the basis of concentration dependence and temperature dependence of the chemical shifts of protons and carbons, and spin‐lattice relaxation times. Antiparallel and/or parallel “in‐register” structures for extended forms and “out‐of‐register” network of extended forms are coexisting in deuterated chloroform solution for these oligopeptides. From the shift for the carbons of the oligopeptides induced by organic acids, it was in ferred that down‐field shifts are induced at α and amide carbons in polypeptides by organic acids. By comparing the induced shift of the carbons in the peptides with the chemical shift differences of the carbons in polypeptides which accompany the helix‐coil transitions, it was found that the conformational changes play a predominant role in the origin of the chemical shift differences of the carbons in polypeptides which accompany the helix‐coil transitions, it was found that the conformational changes play a predominnant role in the orgin of the chemical shift differences of amide, α, β, and γ carbons in polypeptides.
The copolymerization of methacrylaldehyde with hydrophilic monomers
Authors: Schauer Jan , Houska Milan , Kálal Jaroslav 
Published: April 2003

AbstractCopolymers of methacrylaldehyde with hydrophilic monomers — 2‐hydroxyethyl methacrylate, 5‐hydroxy‐3‐oxapentyl methacrylate, 8‐hydroxy‐3,6‐dioxaoctyl methacrylate, N‐ethylmethacrylamide, N,N‐diethylacrylamide, and N,N‐diethylmethacrylamide — were prepared by solution polymerization in N,N‐dimethylformamide initiated with 2,2′‐azodiisobutyronitrile. In the copolymer of methacrylaldehyde (1) with 2‐hydroxyethyl methacrylate (2) (r1 = 0,77, r2 = 0,36) and in the copolymer of methacrylaldehyde with N,N‐diethylacrylamide (r1 = 3,79, r2 = 0,14) the content of CHO groups corresponds to that ot methacrylaldehyde units in the triads comonomer — methacrylaldehyde — comonomer; in the copolymer of methacrylaldehyde with N‐ethylmethacrylamide (r1 = 4,07, r2 = 0,14) both comonomers react with each other and the content of CHO groups is very low, while in the copolymer of methacrylaldehyde with 5‐hydroxy‐3‐oxapentyl methacrylate (r1 = 1,48, r2 = 0,34) the majority of methacrylaldehyde units contain an unreacted CHO group.
Radiation‐induced, solid‐state polymerization of derivatives of methacrylic acid, 10. Polymerizability of barium methacrylate anhydrate
Authors: O'Donnell James H. , Pomery Peter J. , Sothman Robert D. 
Published: April 2003

AbstractWhereas the radiation‐induced polymerization of crystalline barium methacrylate monohydrate has been well established there have been conflicting reports concerning barium methacrylate anhydrate. We have now shown that the yields of high molecular weight polymer are negligible if adequate precautions are taken to prevent polymerization occurring during the separation of polymer from residual monomer. However, monomer losses of up to 80% have been observed by titration of CC bonds with bromine and confirmed by decreases in the appropriate infrared absorptions. X‐ray diffraction studies showed that the crystalline lattice was largely destroyed during the reaction. ESR spectra indicate that initial trapped radicals are converted into propagating radicals with a different conformation than has been reported for the monohydrate.
15N NMR spectroscopy, 22. Influence of shift reagents and paramagnetic ions on the spectra of peptides and polyamides
Authors: Kricheldorf Hans R. , Hull William E. 
Published: April 2003

AbstractThe influence of Eu(dpm)3 and Dy(fod)3 on the 15N NMR spectra of Z‐Gly‐Leu‐Leu‐OMe or Z‐Ala‐Leu‐Leu‐OMe was investigated; however, solvent effects were found to be more useful than shift reagents to improve the spectroscopic structure analysis of peptides. Furthermore, the influence of manganese and copper ions on the Nuclear Overhauser Effect and on the line width of benzyloxycarbonylglycine, polysarcosine, polyglycine and poly(β‐alanine) was investigated in various solvents. The nature of the solvent was found to have a strong influence on the relaxation efficiency of the paramagnetic ions. Manganese ions can be used to shorten the pulse interval without risk of line broadening, when the measurements are carried out under the conditions of “inverse‐gated‐decoupling”.