Showing papers in "Polymer Bulletin in 1981"
TL;DR: The glass transition temperature Tg and to some extent the melting temperature Tm of collagen, cellulose, polyamide 6 and 66, and of the statistical copolyamide 6/66 were investigated with the differential scanning calorimeter after equilibration of the specimens at various humidities at 295K as discussed by the authors.
Abstract: The glass transition temperature Tg and to some extent the melting temperature Tm of collagen, cellulose, polyamide 6 and 66, and of the statistical copolyamide 6/66 were investigated with the differential scanning calorimeter after equilibration of the specimens at various humidities at 295K. The results showed that smaller amounts of absorbed water cause a pronounced shift of Tg to lower temperatures due to the breaking of hydrogen bonds and the reduction of the cohesive energy between the polymer chains. Additional water molecules form clusters with previously absorbed water and Tg decreases are less pronounced. The plasticizing effect of water on natural polymers exceeds by far the effect on synthetic polyamides, as does its influence on Tm in the case of collagen.
113 citations
TL;DR: An ion exchange membrane containing carboxyl groups, insoluble in acidic and alkaline aqueous solutions, was prepared from poly(isobutylene-alternating co-maleic anhydride) and poly(vinyl alcohol).
Abstract: An ion exchange membrane containing carboxyl groups, insoluble in acidic and alkaline aqueous solutions, was prepared from poly(isobutylene-alternating co-maleic anhydride) and poly(vinyl alcohol). Using the membrane in a diaphragm cell, one side being adjusted to be acidic and the other alkaline, it was possible to transport actively and selectively alkali metal ions through the membrane from the alkaline side to the acidic side.
96 citations
TL;DR: In this paper, three-arm telechelic liquid polyisobutylenes carrying exactly three -C(CH3)2Cl endgroups have been synthesized and characterized, and the tertiary chlorine endgroups were quantitatively converted to terminal olefins and these in turn to primary alcohols.
Abstract: Three-arm star telechelic liquid polyisobutylenes carrying exactly three -C(CH3)2Cl endgroups have been synthesized and characterized. Subsequently the tertiary chlorine endgroups have been quantitatively converted to terminal olefins and these in turn to primary alcohols. These terminally trifunctional oligomers are most valuable intermediates for the preparation of networks.
86 citations
TL;DR: The authors showed that temperature affects the stability of commercial polyacrylamide solutions in two different ways: increasing the anionic character of polymers is responsible for the viscosity loss in the presence of monovalent salts and for eventual precipitation in the case of divalent salts even if the molecular weight is not changed.
Abstract: The above reported data show that temperature affects the stability of commercial polyacrylamide solutions in two different ways:
The first process that increases the anionic character of polymers is responsible for the viscosity loss in the presence of monovalent salts and for eventual precipitation in the presence of divalent salts even if the molecular weight is not changed.Such a process will be governed by pH and temperature of oil reservoirs. The second process also leading to decreased viscosity values (even if the extent of hydrolysis is not changed) can be avoided or limited by appropriate precautions (excluding oxygen,adding stabilizers) .
72 citations
TL;DR: In this paper, high-resolution silicon-29 NMR is used to study the microstructure of organosiloxane chain copolymers and three-dimensional cross-linked silicone resins.
Abstract: High resolution silicon-29 NMR is used to study the microstructure of organosiloxane chain copolymers and three-dimensional cross-linked silicone resins. The signal splittings of the Si-29 NMR spectra of methy1-pheny1 siloxane copolymers have been assigned to monomer sequences up to the pentad level and the quantitative microstructure parameters have been estimated. It is shown that Si-29 NMR offers valuable information on the polymer framework of silicone resins both in the liquid and in the solid state.
65 citations
TL;DR: In this paper, aqueous solutions of the polyelectrolytic polysaccharide Xanthan at a concentration of 7.5 % (vol/vol) have long range order very similar to cholesteric liquid crystals.
Abstract: Measurements of birefringence, optical rotation and laser light diffraction show that aqueous solutions of the polyelectrolytic polysaccharide Xanthan at a concentration of 7.5 % (vol/vol) have long range order very similar to cholesteric liquid crystals. The cholesteric screw is left handed implying a rod-like conformation and right handed helicity of individual molecules. The cholesteric phase separates from a less concentrated isotropic solution and spherolites are formed.
60 citations
TL;DR: The acid and enzymic hydrolysis of Kappa carrageenan and the gel permeation chromatography of the charged oligosaccharides are described and the results obtained are compared to previous studies on Na6(CO3)(SO4)2, Na2SO4, and Na2CO3.
Abstract: This paper describes the acid and enzymic hydrolysis of Kappa carrageenan and the gel permeation chromatography of the charged oligosaccharides.
56 citations
TL;DR: In this article, the effect of size, shape and phase volume on the shear storage and loss moduli of a model system of glass filled gelatin gels has been investigated by using well characterised samples of glass spheres, rods and irregular pieces of intermediate shape.
Abstract: Small deformation mechanical measurements were performed on the model system of glass filled gelatin gels. By using well characterised samples of glass spheres, rods and irregular pieces of intermediate shape, e.g. plates at varying phase volume of filler, the effect of size, shape and phase volume on the shear storage and loss moduli could be investigated.
53 citations
TL;DR: In this article, the charge distribution in the thickness direction of 10 to 100 μm thick polymer electrets can be determined with a new method utilizing a <1 ns laser pulse to launch a pressure pulse in the sample.
Abstract: The charge distribution in the thickness direction of 10 to 100 μm thick polymer electrets can be determined with a new method utilizing a <1 ns laser pulse to launch a pressure pulse in the sample. Propagation of the pressure pulse through the film causes electrode currents which yield the charge distribution. The method has been applied to electron-beam charged PETP and FEP samples.
51 citations
TL;DR: In this paper, the authors measured the 13C NMR spectra with respect to the secondary structure and found that the peak areas are proportional to the mole ratios of the different secondary structures and neither a mismatch of the Hartmann-Hahn conditions nor variations of the mixing time or the pulse interval have a significant influence on the intensity ratios.
Abstract: 75.46 MHz 13C-NMR CP/MAS spectra of solid poly(1-alanines) with various degrees of polymerization were measured. The signals of all three carbons are split into two peaks. One peak presents the α-helix structure and one the pleated sheet form. Equimolar mixtures of helical poly(L-alanine) with poly(glycine) and poly(L-valine) were measured under various conditions. It was found that the peak areas are proportional to the mole ratios of the different secondary structures and neither a mismatch of the Hartmann-Hahn conditions nor variations of the mixing time or the pulse interval (relaxation delay) have a significant influence on the intensity ratios. Hence, a quantitative evaluation of the 13C NMR spectra with respect to the secondary structure is feasible.
41 citations
TL;DR: In this paper, the conformation of single chains in bulk polymer materials can be evaluated from coherent neutron scattering on mixtures of normal and deuterated polymers, and it is shown that the single-chain structure factor can be also obtained from measurements of highly concentrated mixtures.
Abstract: The conformation of single chains in bulk polymer materials can be evaluated from coherent neutron scattering on mixtures of normal and deuterated polymers. It is shown that the single-chain structure factor can be also obtained from measurements of highly concentrated mixtures and the procedure of evaluation is described. The application to amorphous polycarbonate demonstrates the advantages of the method.
TL;DR: In this paper, the tensile strength at break of polyethylene fibers was investigated at room temperature under vacuum by means of 60Co γ-radiation and it was concluded that stressed chains break preferentially upon irradiation.
Abstract: Ultra-high strength polyethylene fibers, with a tensile strength at break varying from 1.6 up to 3.5 GPa, were irradiated, at room temperature under vacuum by means of 60Co γ-radiation. Sol-gel analysis showed a ratio of crosslinking to main-chain scissioning of about 1. The tensile strength at break decreased upon irradiation. The decrease of tensile strength at break depended on initial fiber strength and could be attributed to main-chain scissioning. It was concluded that stressed chains break preferentially upon irradiation. “Fiber” networks exhibited a deformation ratio of 16 during stress-strain measurements.
TL;DR: In this paper, a macromonomer and sebacic acid were condensed with diamines by triphenylphosphitepyridine system, and graft copolyamides of well-defined structure and composition were readily prepared.
Abstract: Dicarboxyl-terminated macromolecular monomers (macromonomers) were synthesized by radical polymerization of methyl methacrylate in the presence of thiomalic acid as a chain transfer agent. This macromonomer and sebacic acid were condensed with diamines (p,p′-diaminodiphenyl ether, p,p′-diaminodiphenylmethane and m-phenylenediamine) by triphenylphosphitepyridine system. Thus, graft copolyamides of well-defined structure and composition were readily prepared. This is the first example of the polycondensation reactions of macromonomers.
TL;DR: In this article, the transformation of the β-modification into α -modification in isotactic polypropylene was investigated by WAXS, DSC and dilatometric methods.
Abstract: The transformation of the β-modification into α-modification in isotactic polypropylene was investigated by WAXS, DSC and dilatometric methods. The temperature and time dependent WAXS spectra were made by using high-intensity synchrotron radiation. The β -α transformation was followed by short time exposures. The transformation of the β-modification was found to act toward the increase in the total crystallinity.
TL;DR: In this article, the effect of temperature on the chemical and thermal stability of polyacrylamide solutions was investigated using viscosity and light scattering data, and it was shown that no polymer degradation due to oxygen contamination results from heating polymer solutions although higher temperature is responsible for hydrolysis of amide groups.
Abstract: We have investigated the effect of temperature on the chemical (hydrolysis) and thermal (molecular weight) stability of purified polyacrylamide solution.From viscosity and light scattering data we show that no polymer degradation due to oxygen contamination results from heating polymer solutions although higher temperature is responsible for hydrolysis of amide groups.
TL;DR: In this paper, a copolymerization of ethylene with propylene was conducted over the thermally reduced γ-Al2O3-supported TiCl4 catalyst both in the absence or presence of AlEt3.
Abstract: Copolymerization of ethylene with propylene was conducted over the thermally-reduced γ-Al2O3-supported TiCl4 catalyst both in the absence or presence of AlEt3 (or AlEt2Cl). It was found that the structure of the polymer drastically changed from a random copolymer to polyethylene with an increase in the concentration of AlEt3. A plausible mechanism was proposed for the copolymerization.
TL;DR: In this article, the activation process of this secondary relaxation obeys to an Arrhenius-type dependence and an activation energy of 30.5 Kcal/mole is calculated.
Abstract: Halato-telechelic polymers (HTP) resulting from the neutralization of carboxy telechelic polymers behave as useful ion-containing model compounds. Carboxy telechelic polybutadiene (\(\overline {Mn} :4,600\)) neutralized by magnesium methoxide exhibits a secondary relaxation mechanism characteristic of the ionic component. The activation process of this secondary relaxation obeys to an Arrhenius-type dependence and an activation energy of 30.5 Kcal/mole is calculated.
TL;DR: In this article, the melting behavior of acrylic copolymers in the wet and dry state is explained in terms of the Eby model of a polymer crystal whereby the non-crystallizable comonomers enter the crystal lattice as defects.
Abstract: An unconventional thermal analytical technique has been developed for acrylic polymers. By adding water to the polymer the melting point is depressed well below the onset temperature of cyclic thermal degradation. This addition of water depresses the melting point of polyacrylonitrile from 320°C to 185°C. The melting behavior of acrylic copolymers in the wet and dry state is explained in terms of the Eby model of a polymer crystal whereby the non-crystallizable comonomers enter the crystal lattice as defects. The melting point and heat of fusion are interpreted as a measure of the regularity and strength of the intermolecular dipolar bonding that stabilizes the lattice.
TL;DR: In this article, the molecular architecture of linear and threearm star polyisobutylenes prepared by the use of bi- and trifunctional inifers (binifers and trinifers), respectively, has been analyzed.
Abstract: SummaryThe molecular architecture of linear and threearm star polyisobutylenes prepared by the use of bi- and trifunctional inifers (binifers and trinifers), respectively, has been analyzed. In particular, the number of polyisobutylene arms emanating from the central aromatic inifer residue and their molecular weights ¯Mn have been determined. The analytical technique developed for this purpose consists of a selective and quantitative oxidative degradation of the central aromatic inifer residue with CF3COOH-H2O2 mixtures in conjunction with ¯Mn determinations before and after degradation.
TL;DR: For the first time, a living living lactam polymerization was proved by choosing the proper type of polymerization, lactam, growth center as well as initiator.
Abstract: For the first time, a living lactam polymerization was proved by choosing the proper type of polymerization, lactam, growth center as well as initiator. The anionic polymerization of the disubstituted four-membered lactam (I) initiated with its lithium salt in the presence of the N-pivaloyl derivative of I acting as the growth center yielded almost monodisperse polymers of I. Subsequent additions of monomer I increased the molecular weight proportionally without appreciable changes of the MWD and number of polymer molecules.
TL;DR: In this article, the 1.13C spin-lattice relaxation rate of solid PMMA has been measured with CP MAS NMR and isotactic, atactic, syndiotactic, and 1∶2 i-s PMMA complex were measured, along with atactic samples containing bisdioxan or the monomer as a plasticizer.
Abstract: 13C spin-lattice relaxation rates R1 in samples of solid PMMA have been measured with CP MAS NMR. Isotactic, atactic, syndiotactic, and the 1∶2 i-s PMMA complex were measured, along with atactic samples containing bisdioxan or the monomer as a plasticizer. The reorientation of the α-methyl protons is the dominant relaxation source for the methylene, α-methyl and quarternary carbon nuclei. Increased mobility of the polymer in the presence of a plasticizer is not reflected in significant changes in R1.
TL;DR: In this paper, the 300 MHz pmr spectrum of poly(2-vinyl thiophene), poly-2-VT, is presented and analyzed, and the aliphatic proton resonance of this polymer is very similar to that of polystyrene, but the aromatic proton Resonance is rather well defined.
Abstract: The 300 MHz pmr spectrum of poly(2-vinyl thiophene), poly-2-VT, is presented and analyzed. The aliphatic proton resonance of this polymer is very similar to that of polystyrene, but the aromatic proton resonance is rather well defined, especially that of protons in the 3-position of the thiophene ring. The resonance of such protons occurs as a three peak pattern that has been interpreted in terms of pentad stereosequences. Based on the assignments made in this paper, poly-2-VT prepared by free radical initiated polymerization seems to be atactic.
TL;DR: In this paper, a graftcopolymerization of methyl methacrylate macromonomer with perfluoroalkyl acrylate was performed to improve water repellent surfaces.
Abstract: Well-defined graftcopolymers were prepared by radical copolymerization of methyl methacrylate macromonomer with perfluoroalkyl acrylate Contact angle of the solvent cast films of poly(methyl methacrylate) containing various amount of the graftcopolymer was measured against water droplet Addition of 02 wt% of the graftcopolymer was sufficient to improve the polymer films to water repellent surfaces, while 10 wt% was necessary to modify the polymer surfaces to the same level of water repellency
TL;DR: In this article, the active species (aziridinium ion) of living poly(1-tert.butyl aziridine) by methacrylic acid leads to the corresponding polyamine-methacrylate ester macromer.
Abstract: Desactivation of the active species (aziridinium ion) of living poly(1-tert.butyl aziridine) by methacrylic acid leads to the corresponding polyamine-methacrylate ester macromer. Macromers of different molecular weights were characterized by gel permeation chromatography and by 360 MHz 1H NMR spectroscopy.
TL;DR: In this article, the microstructure sensitive fluorescence polarization method was used to measure the segmental density of styrene-divinylbenzene copolymerization in pre-and post-gel state at various degrees of conversion depending on the initial composition of reaction mixture.
Abstract: If styrene-divinylbenzene copolymerization is performed at certain conditions of network formation, regions of relative high segmental density may occur. The segmental density can be monitored directly by the microstructure sensitive fluorescence polarization method. Measurements were made in the pre- and post-gel state at various degrees of conversion depending on the initial composition of the reaction mixture. The results, particularly in situations of high crosslinker content support the currently used models of network formation mechanisms during crosslinking copolymerization.
TL;DR: Experimental evidence is presented indicating that intermolecular oligomerization of CN groups takes place, and possibly has an even greater importance than the intramolecular reaction (leading to "ladder polymer" as discussed by the authors ).
Abstract: Experimental evidence is presented indicating that intermolecular oligomerization of CN groups (leading to crosslinked structures) takes place, and possibly has an even greater importance than the intramolecular reaction (leading to “ladder polymer”), at higher temperatures. The easy, quasi “built-in” crosslinking upon heat treatment is considered the most significant single feature with regard to making polyacrylonitrile and its copolymers unique among synthetic polymers as a carbon fiber precursor.
IBM1
TL;DR: In this paper, the rotational isomeric state model satisfactorily accounts for IANS and chain dimensions of polycarbonate in the amorphous state and provides compelling evidence that adjacent re-entry is rare.
Abstract: Molecular scattering functions at intermediate scattering vectors, of μ=(4π/λ sinϑ/2) in the range 0.03 to 1.0A−1, are found to be extremely sensitive to the local configurations of polymer chains in both semicrystalline and amorphous states. Available experimental results of intermediate angle neutron scattering (IANS) from melt-crystallized polyethylene and isotactic polypropylene provide compelling evidence that adjacent re-entry is rare. The rotational isomeric state model satisfactorily accounts for IANS and chain dimensions of polycarbonate in the amorphous state.
TL;DR: In this paper, the substitution reaction with NaSC6H5 was studied for two samples of PVC having very different tacticities, and it was concluded that the observed very fast initial period of the reaction involves selectively a small fraction of isotactic and heterotactic triads, and such triads are likely to be considered as labile structures in PVC.
Abstract: The substitution reaction with NaSC6H5 is studied for two samples of PVC having very different tacticities. From both the kinetic results and the thermal degradation of the modified polymers it is concluded that the observed very fast initial period of the reaction involves selectively a small fraction of isotactic and heterotactic triads, and that such triads are likely to be considered as labile structures in PVC. The results are therefore a contribution to the understanding of the thermal instability of PVC.
TL;DR: In this paper, a Brillouin spectrometer has been used to show that transition-like phenomena exist in the melt of low molecular weight polyethylene (Mn=2230), and the sound velocity gradient is a constant above and below Tu=436 K in a wide temperature range, but is discontinuous at Tu.
Abstract: A new type of Brillouin spectrometer has been used to show that transition-like phenomena exist in the melt of low molecular weight Polyethylene (Mn=2230). Because of the enhanced accuracy of the new spectrometer it could be shown that the sound velocity gradient is a constant above and below Tu=436 K in a wide temperature range, but is discontinuous at Tu. The same hypersonic behaviour has been found for MBBA at the nematic-isotropic-transition. NMR investigations have confirmed the existence of Tu previously reported for n-Tetracosane (C24H50).
TL;DR: In this paper, a SiO2-supported CoCl2 catalyst was prepared by supporting the complex of CoCl 2 2C5H5N on SiO 2 in n-heptane, followed by evacuating at room temperature.
Abstract: A highly dispersed SiO2-supported CoCl2 catalyst was prepared by supporting the complex of CoCl2 2C5H5N on SiO2 in n-heptane, followed by evacuating at room temperature. The catalyst combined with AlEt2Cl showed a very high activity for the polymerization of isoprene.