Showing papers in "Polymer Bulletin in 1982"
TL;DR: In this paper, a broad multiplicities of the C-4 and C-6 resonance lines in a similar manner as those of native cellulose samples such as cotton and ramie were investigated.
Abstract: CP/DD/MASS 13C-NMR spectra have been obtained for regenerated cellulose samples with different crystallinities as well as for cotton, β-D-glucose, β-D-cellobiose, and cellopentaose. The spectra of the regenerated cellulose samples exhibit broad multiplicities of the C-4 and C-6 resonance lines in a similar manner as those of native cellulose samples such as cotton and ramie, and, in addition, another broad tailing of the C-1 resonance. Since these multiplicities change linearly with crystallinity, it is concluded that they are ascribed to the contributions from the crystalline and noncrystalline components. Effects of hydrogen bonds and conformations of the β-1,4-glycosidic linkage on the chemical shifts are also discussed.
116 citations
TL;DR: In this article, a living radical mechanism was proposed for photopolymerization of styrene (St) with diphenyl disulfide (DPD), tetraethyl thiuram disulfides (TD), benzyl diethyldithiocarbamate (BDC), and 2-phenylethyl diethyl diethiocarbamide (PEDC) as photoiniferters.
Abstract: Some examples for living radical polymerization in homogeneous solution by four organic sulfides as photoiniferters have been proposed. In the photopolymerization of styrene (St) with diphenyl disulfide (DPD), tetraethyl thiuram disulfide (TD), benzyl diethyldithiocarbamate (BDC) and 2-phenylethyl diethyldithiocarbamate (PEDC), both the yields and the average-molecular weights of the polymers were found to increase as a function of the reaction time. The results obtained suggested that these polymerizations proceeded via a living radical mechanism. When these photoiniferters except DPD were used, the propagating polymer chain end was confirmed to be always the diethyldithiocarbamate [(C2 H5)2NCSS] group, which can further photodissociate into a reactive propagating radical and a less reactive small radical[(C2H5)2NCSS·] in order to result in successive insertion of monomer molecules into the dissociated bond.
94 citations
TL;DR: In this paper, a scheme has been proposed which shows the sequence of reactions leading to indane skeletons, and the structure of the indane derivatives has been characterized by 1H NMR spectroscopy.
Abstract: The possibility of undesirable intramolecular cycloalkylation exists in the polymerization of iso-butylene induced by the p-dicumyl chloride/BCl3 inifer system. A scheme has been proposed which shows the sequence of reactions leading to indane skeletons. The structure of the indane derivatives has been characterized by 1H NMR spectroscopy. Systematic experiments have been carried out using low isobutylene and high p-dicumyl chloride concentrations leading to polyisobutylene oligomers needed for accurate endgroup analysis. The effect of temperature, solvent composition (polar/nonpolar) , isobutylene and BCl3 concentration on the extent of indane skeleton formation has been investigated. Indane skeleton formation can be completely suppressed by the use of relatively non-polar media, e.g., 1∶1 mixture of CH2Cl2 :n-C6H14, at or below −40°C, and conditions under which symmetrical telechelic polyisobutylenes can be obtained have been defined.
89 citations
TL;DR: A quantitative product analysis has shown that these inhibitors react by hydrogen abstraction from a thermally generated styrene dimer (1phenyl-1,2,3,9-tetrahydronaphthalene) and to a minor extent by addition to the double bond of styrene monomer as mentioned in this paper.
Abstract: The efficient free radical scavengers 1,1,3,3-tetramethylisoindolinyl 2-oxy and 2,2,6,6-tetramethylpiperidinyl-1-oxy (nitroxides) disappear in styrene at 100°C with near zero order kinetics but at rates which are some 20 times higher than the known rate of initiation of thermal polymerization in the absence of scavenger A quantitative product analysis has shown that these inhibitors react by hydrogen abstraction from a thermally generated styrene dimer (1-phenyl-1,2,3,9-tetrahydronaphthalene) and to a minor extent by addition to the double bond of styrene monomer
84 citations
TL;DR: In this paper, the electric field induced cooperative structure transition of a liquid crystalline poly(poly{1]-6-[4-N-(4-cyanophenyl)iminomethylphenoxy] hexyloxycarbonyl] ethylene was investigated.
Abstract: SummaryElectro-optical behaviour of a liquid crystalline polymer- poly{1-[6-[4-N-(4-cyanophenyl)iminomethylphenoxy] hexyloxycarbonyl] ethylene}- is studied A sharp change of the optical properties measufred in crossed polarizers under the cooling of the preliminary oriented sample in an electric field is observed. The effect is explained from the viewpoint of the electric field induced cooperative structure transition.
70 citations
TL;DR: In this paper, the base catalyzed reaction between epoxide and carboxyl groups was studied using a simple model system phenylglycidyl ether-caproic acid in the presence of triethylamine.
Abstract: The base catalyzed reaction between epoxide and carboxyl groups was studied using a simple model system phenylglycidyl ether-caproic acid in the presence of triethylamine. The reaction was investigated by mass spectrometry and GPC which provide an overall qualitative and quantitative survey of all the forming reaction products. The addition esterification is followed by etherification and condensation esterification and the main reaction product, monoester, is disproportionated yielding diester and diol. In a polyfunctional system, the latter reaction may cause splitting of the polymer chain and formation of new crosslinks.
66 citations
TL;DR: In this article, the effect of concentration of the crosslinking agent on the swelling equilibrium and mechanical behaviour of poly(acrylamide) gels with a low content of sodium methacrylate (molar fraction xMNa = 0.012) was investigated in acetone-water mixtures.
Abstract: The effect of concentration of the crosslinking agent on the swelling equilibrium and mechanical behaviour of poly(acrylamide) gels with a low content of sodium methacrylate (molar fraction xMNa = 0.012) was investigated in acetone-water mixtures. The increasing concentration of the crosslinking agent suppresses the extent of phase transition Δ (determined by a change in the gel volume) and decreases the critical value of the interaction parameter χc (given by the composition of the acetone-water mixture) at which the collapse takes place; these dependences are in a semiquantitative agreement with the recent molecular theory which describes the swelling equilibria of polyelectrolyte networks.
63 citations
TL;DR: In this paper, a strong multiphase elastomeric siloxane-urea copolymers were synthesized from MDI and α, ω-bis(aminopropyl)polydimethylsiloxane of different molecular weights by solution polymerization, using 2-ethoxyethyl ether as the solvent.
Abstract: Siloxane-urea copolymers were synthesized from MDI and α, ω-bis(aminopropyl)polydimethylsiloxane of different molecular weights by solution polymerization, using 2-ethoxyethyl ether as the solvent. Chain extenders were also employed in some reactions. Formation of urea linkages were followed by FTIR spectroscopy. The products were characterized by GPC chromatography and intrinsic viscosity measurements. Thermal (DSC) and thermomechanical (TMA) characterization of the products were also carried out. The results indicate the formation of novel, strong multiphase elastomeric siloxane-urea copolymers.
60 citations
TL;DR: In this article, the homopolymerization of ethylene, propylene, 1-hexene and 1,3-butadiene was conducted over the SiO2-supported TiCl4 catalyst using either AlEt2Cl or alEt3 as a reducing reagent.
Abstract: Both the homopolymerization of ethylene, propylene, 1-hexene and 1,3-butadiene and the copolymerization of ethylene with these monomers were conducted over the SiO2-supported TiCl4 catalyst using AlEt2Cl or AlEt3 as a reducing reagent. With an increase in the concentration of AlEt3, the polymerization activities except for ethylene markedly decreased and the structures of the copolymers drastically changed to polyethylene. From these results, a correlation was established between the oxidation states of titanium and the polymerization activities for these monomers.
52 citations
TL;DR: In this article, anionic living polymerization of oxirane was shown to be efficient for the synthesis of polyethylene oxide macromers, which were characterized carefully to establish quantitatively the presence of the end-standing double bond.
Abstract: Anionic “living” polymerization of oxirane was shown to be efficient for the synthesis of polyethylene oxide macromers. The double bond at chainend was introduced either upon initiation or upon deactivation. The macromers obtained were characterized carefully to establish quantitatively the presence of the end-standing double bond. The species are well defined and of narrow molecular weight distribution.
51 citations
TL;DR: In this paper, the properties of low and high-molecular-weight liquid crystals are combined in a single polymer, and this opens up new prospects for their use by significantly extending the number of liquid-crystalline compounds.
Abstract: Investigators in the field of physical chemistry of macromolecular compounds have recently turned to problems in the creation and study of polymeric liquid-crystalline (LC) systems [1–25]. The great interest in these systems is due to the significant advances in the study and practical application of low-molecular-weight liquid-crystals in such new fields of technology as electronics, electrooptics, holography, etc., as well as in medicine, chemistry, and biology [26–32]. On the other hand, the interest in this field is also due to the possibility of creating polymer systems which successfully combine the unique properties of low-molecular-weight liquid crystals and low-molecular-weight compounds, which allows for the preparation of films, fibers, and coatings with unusual properties. The use of low-molecular-weight thermotropic liquid crystals in most cases involves the creation of special hermetic membranes (electro-optical cells, microcapsules, etc.) which form the required shape and protect the LC compound from external effects. In the case of thermotropic LC polymers, the creation of these shapes can be and is optional, since the properties of low-and high-molecular-weight liquid crystals are combined in a single polymer, and this opens up new prospects for their use by significantly extending the number of LC compounds.
TL;DR: In this article, it was found that the three-phase heterogeneous reaction of propane sultone with macroporous glycidylmethacrylate copolymers in an aqueous alkaline medium proceeds to a higher degree in presence of phase transfer catalyst.
Abstract: SummaryIt has been found that the three-phase heterogeneous reaction of propane sultone with hydrolyzed macroporous glycidylmethacrylate copolymers in an aqueous alkaline medium proceeds to a higher degree in presence of phase transfer catalyst. The best results were obtained using tetra(n-butyl)ammonium hydroxide. An important finding is the increase in the degree of transformation of the reaction in flow arrangement compared with the batch procedure. The influence of phase transfer catalyst is also more effective. The reaction is discussed with respect to the properties of the products, i.e. of the overall and surface contents of groups introduced into the reaction, of the specific surface area and specific pore volume of sulfopropylated copolymers.
TL;DR: In this paper, cross-polarization spectra of solid polymers can be misleading when the material exhibits proton spinlattice relaxation in the rotating frame which cannot be represented by a single exponential.
Abstract: Cross-polarization spectra of solid polymers can be misleading when the material exhibits proton spinlattice relaxation in the rotating frame which cannot be represented by a single exponential. Quantitative and qualitative demonstrations of the problem are given. The use of two experimental procedures for alleviating the difficulties is suggested, and examples for polyalkenes and for polyethylene terephthalate are illustrated.
TL;DR: In this paper, a living radical mechanism was proposed to synthesize block copolymers with the polymers obtained by tetraethyl thiuram disulfide(TD) as polymeric photoiniferters.
Abstract: To synthesize efficiently block copolymers, the radical polymerization of vinyl monomers with the polymers obtained by tetraethyl thiuram disulfide(TD) as polymeric photoiniferters has been investigated. These photopolymerizations were found to proceed via a living radical mechanism, i.e. both the whole polymer yields and the average molecular weight of the block copolymers increased with increasing of the polymerization time. By applying these living radical polymerizations, various block copolymers consisting of two, three and four component blocks were obtained in good yields, suggesting that these techniques are effective and useful for synthesizing multi component block copolymers through radical polymerizations of polar vinyl monomers.
TL;DR: In this article, the authors found that a steep increase takes place in an ordinary Mooney-Rivlin plot not only for natural rubber but also for non-crystallizable rubbers such as SBR, NBR, EPDM and polyurethane.
Abstract: The rubber elasticity increases in general at very large elongation and sometimes it is ascribed to the strain-induced crystallization. However, the authors found that a steep increase takes place in an ordinary Mooney-Rivlin plot not only for natural rubber but also for non-crystallizable rubbers such as SBR, NBR, EPDM and polyurethane, and the upturn for non-crystallizable rubbers disappears if data are examined with the theoretical equation derived taking the limited extensibility of chains into consideration. In the ordinary Mooney-Rivlin plot the elongation inducing the stress upturn due to the limited extensibility of chains increases with decreasing degree of vulcanization and sometimes it does not appear before the upturn of the rubber of low degree of vulcanization. The strain-induced crystallization can bring about the steep increase of elastic force, but it is not always adequate to ascribe the upturn to the strain-induced crystallization. The upturn also occurs due to the limitation of extensibility of chains.
TL;DR: In this article, the validity of the copolymerization of macromers with small monomers for the preparation of graft copolymers has been examined, and the reactivity ratios of high molecular weight macromer r1 cannot be determined experimentally with sufficient accuracy whereas those of small monomer r2 may be calculated by r2=ln(1-p2)/ ln( 1-p1) where p1 and p2 are the respective conversions of the macrommer and small-monomer.
Abstract: The validity of the copolymer composition equation for the copolymerization of macromers with small monomers for the preparation of graft copolymers has been examined. The reactivity ratios of high molecular weight macromers r1 cannot be determined experimentally with sufficient accuracy whereas those of small monomers r2 may be calculated by r2=ln(1-p2)/ ln(1-p1), where p1 and p2 are the respective conversions of the macromer and small monomer. A single experimental datum obtained even at high conversions may be used. The error of the method can be readily calculated.
TL;DR: In this article, the effect of hydrogen on the molecular weight of propylene was examined with the soluble and insoluble fractions in boiling n-heptane, and it was found that the chain transfer reaction of the atactic and isotactic polymers took place via an atomic hydrogen and a molecular hydrogen, respectively.
Abstract: Polymerization of propylene was conducted at 40 °C with the catalytic system of TiCl4/MgCl2/ Al (C2H5)3/ethyl benzoate using hydrogen as a chain transfer agent, and the effect of hydrogen on the molecular weight was examined separately with the soluble and insoluble fractions in boiling n-heptane. It was found that the chain transfer reaction of the atactic and isotactic polymers took place via an atomic hydrogen and a molecular hydrogen, respectively. The result strongly supports the previous mechanism that there exist two types of polymerization centers, one having two vacancies which gives the atactic polymer and the other having one vacancy which gives the isotactic polymer.
TL;DR: In this paper, the synthesis of these glycidyl ethers involved quantitative condensation of epichlorohydrin with phenol-capped linear or three-arm star polyisobylenes.
Abstract: SummaryGlycidyl ethers of bisphenol- and trisphenol-polyisobutylenes have been prepared, characterized, and cured with amines to new flexible epoxy resins. The synthesis of these glycidyl ethers involved quantitative condensation of epichlorohydrin with phenol-capped linear or three-arm star polyisobutylenes. Proton NMR analysis of the model compound monoglycidyl ether of 2,4,4-trimethyl-2(p-hydroxyphenyl)pentane and the corresponding glycidyl ethers of phenol-capped polyisobutylenes showed the presence of epoxy end groups. According to 1H NMR spectroscopy and titration data the number-average terminal epoxy functionality is close to the theory, i.e., two or three, for the linear and three-arm star products. Curing these new epoxides with triethylene tetramine resulted in transparent, non-tacky flexible films.
TL;DR: In this article, a polyisobutylene-based polyurethane network was synthesized by crosslinking polyisometylene glycols with tri-phenylmethane triisocyanate and their gas permeability, water absorption, hydrolytic stability, and air oven aging characteristics was examined by ASTM methods.
Abstract: Polyisobutylene-based polyurethane networks have been synthesized by crosslinking polyisobutylene glycols with tri-phenylmethane triisocyanate and their gas permeability, water absorption, hydrolytic stability, and air oven aging characteristics was examined by ASTM methods. The preparation of the polyurethane sheets is described. The oxygen permeability of polyisobutylene-based polyurethanes is lower than that of vulcanized butyl rubber and their water absorption is negligible. The hydrolytic stability of these new polyurethanes is outstanding and their mechanical properties (tensile strength, modulus, elongation) remain practically unchanged after four days of exposure to 85° steam. Similarly, air aging for two days at 128° affects little mechanical properties.
TL;DR: In this article, the synthesis and quantitative end group characterization of bisphenol- and trisphenolate-polyisobutylenes are described, which are obtained by quantitative Friedel-Crafts alkylation of phenol by olefin-and/or tert.-chlorine-telechelic PIB's and involved 1H NMR, UV and GPC techniques.
Abstract: SummaryThe synthesis and quantitative end group characterization of bisphenol- and trisphenol-polyisobutylenes are described. These new telechelic prepolymers consist of a linear or a threearm star polyisobutylene (PIB) carrying exactly two or three phenol termini, respectively. The syntheses were accomplished by quantitative Friedel-Crafts alkylation of phenol by olefin- and/or tert.-chlorine-telechelic PIB's and characterization involved 1H NMR, UV and GPC techniques. These materials combine the chemical versatility of the- C(CH3)2C6H4OH end group with the attractive physical-chemical properties of the rubbery PIB chain.
TL;DR: In this paper, the melting and crystallization of PAN and acrylonitrile-vinyl acetate copolymers are studied as a function of water content. And the latter relationships are examined in terms of the acrylic polymer morphology and the possibility that the water molecules become associated with the nitrile group during the melting process.
Abstract: Water is known to strongly depress the melting point of polyacrylonitrile (PAN) and acrylic copolymers. A scanning calorimetric technique has been developed that utilizes this melting point depression in probing the structure of acrylic fibers. In this report the melting and crystallization of PAN and acrylonitrile-vinyl acetate copolymers is studied as a function of water content. Addition of water continually depresses the polymer melting point until a critical water level is reached where the molten polymer separates from the water and no further reduction in the melting point is observed. Both the minimum melting point and the critical amount of water required for phase separation decreases as the level of vinyl acetate comonomer is increased. The latter relationships are examined in terms of the acrylic polymer morphology and the possibility that the water molecules become associated with the nitrile group during the melting process.
TL;DR: In this paper, changes in the size and broadening distribution of linear polyethylene fractions were studied using low frequency Raman spectroscopy (LAM) for isothermal crystallization.
Abstract: Changes in the crystallite size distribution during the isothermal crystallization of linear polyethylene fractions were studied using low frequency Raman spectroscopy (LAM). Increases in the crystallite size and broadening distributions were observed as a function of time for all molecular weights studied. Large increases in size occurred even after most of the isothermal crystallinity had formed. The rate of increase was faster for higher crystallization temperatures, while the process was retarded for the higher molecular weights. Similar results were obtained for an unfractionated polymer except for complications that are likely due to molecular weight fractionation.
TL;DR: The crystallization of cyclic oligomers occurs in commercial films of poly(ethyleneterephthalate) upon annealing the films above 100°C or exposing to solvent vapor as discussed by the authors.
Abstract: The crystallization of cyclic oligomers occurs in commercial films of poly(ethyleneterephthalate) upon annealing the films above 100°C or exposing to solvent vapor. The size of the crystals increase with time and temperature of annealing. The crystals obtained on annealing are in the form of hexagonal prisms whereas they are in the form of cylindrical prisms on exposure to solvent vapor.
TL;DR: In this article, the number average molecular weights (¯Mn's) of tri-arm polyisobutylene based ionomers were varied from 8,300 to 34,000.
Abstract: Mechanical properties of tri-arm polyisobutylene based ionomers have been investigated. Number average molecular weights (¯Mn's) of the polymers were varied from 8,300 to 34,000. The ionomer of lowest ¯Mn (8,300) exhibits very low extension at break (∼ 150%) while the others with ¯Mn's of 11,000, 14,000 and 34,000 show very high extensions, often exceeding 1,000%, and display relatively low permanent set and low hysteresis behavior. Since the ionic bonding is located exclusively at the chain ends, end-linked pseudo networks are formed due to coulombic attractions.At higher temperatures the coulombic interactions are weakened and the networks can be compression molded (∼150°C).
TL;DR: In this article, the results of a physico-chemical characterization by means of XRD (cristallinity index) and DSC techniques are related to the microstructure of the polymers, as determined by 19F NMR.
Abstract: Hexafluoropropene (HFP) — 1,1-difluoroethene (VDF) copolymers have been synthesized in the 0–16 mole % HFP range and the results of a physico-chemical characterization by means of XRD (cristallinity index) and DSC techniques are related to the microstructure of the polymers, as determined by 19F NMR. The addition of a small percentage of the HFP comonomer does not affect the polymorphism of poly(vinyl-idenefluoride).
TL;DR: In this paper, the statistical theory of branching processes has been used in an analysis of gelation in the system diepoxide-cyclic anhydride-tert.-amine in step and initiated reaction mechanisms.
Abstract: The statistical theory of branching processes has been used in an analysis of gelation in the system diepoxide-cyclic anhydride-tert.-amine in step and initiated reaction mechanisms. Experimental data indicate that critical conversion depends on the concentration of tert.-amine, which suggests that a mechanism with initiation is operative.
TL;DR: In this paper, a dihydroxyl-terminated macromonomer and 1,4-butanediol were added to diisocyanate to produce tailor-made graft copolymers.
Abstract: Polyurethane-poly(methyl methacrylate) graft copolymers of well-defined structure and composition were synthesized by macromonomer method. Dihydroxyl-terminated macromonomer was prepared by radical polymerization of methyl methacrylate in the presence of α-thioglycerol as a chain transfer agent. This dihydroxyl-terminated macromonomer and 1,4-butanediol were added to diisocyanate (hexamethylene diisocyanate or toluene-2,4-diisocyanate) catalyzed by di-n-butyltin dilaurate to produce tailor-made graft copolymers.
TL;DR: The interaction of γ-cyclodextrin (γ-CD) with sodium 1-pyrenesulfonate (PS) was studied spectrophotometrically and it was found to cause much larger decrease in the absorption maxima of PS than β-CD.
Abstract: The interaction of γ-cyclodextrin(γ-CD) with sodium 1-pyrenesulfonate(PS) was studied spectrophotometrically. γ-CD was found to cause much larger decrease in the absorption maxima of PS than β-CD. The fluorescence spectra of PS in the presence of γ-CD showed excimer emission, while those of PS with β-CD showed only monomer emission, indicating that γ-CD forms 1∶2 (γ-CD∶PS) complexes in which two PS molecules are included in the γ-CD cavity in a face-to-face fashion. The binding isotherm showed a sigmoidal curve. The association constants were estimated by computer simulation of the binding curve. The 1∶2 (CD∶PS) complex was found to be much more stable (K=106 M−1) than the 1∶1 complex (K=1 M−1). At high concentration of γ-CD another γ-CD cooperates in binding two PS molecules, resulting in the formation of a 2∶2 complex.
TL;DR: In this paper, a new method for determining copolymerization reactivity ratios by using high resolution gel permation chromatography was described, which involves a macromer and the separation of each monomer, copolymers and solvent allows calculation of concentration of reactants and products.
Abstract: In this paper is decribed a new method for determining copolymerization reactivity ratios r by using high resolution gel permation chromatography. The system of monomers is a new one involving a macromer. Separation of each monomer, copolymer and solvent allows calculation of concentration of reactants and products, so as the copolymer molecular weight distribution.