Showing papers in "Polymer Journal in 1986"

Living and Highly Isotactic Polymerization of Methyl Methacrylate by t-C4H9MgBr in Toluene

Abstract: Highly isotactic PMMAs with narrow molecular weight distribution (Mw/Mn<1.2) have been prepared by the polymerization of MMA in toluene at −78°C initiated by t-C4H9MgBr prepared in diethyl ether. The polymerization proceeded in a “living” manner, in which the initiation reaction was fast and quantitative whereas the propagation was slow. The ether solution of t-C4H9MgBr used as the initiator contained almost equal amounts of MgBr2 produced by an Wurtz type coupling during the preparation. It has been found from 1H NMR analyses that the excess amount of MgBr2 contributes to form the initiating species of homogeneous activity and stereospecificity. Polymerizations of MMA by n-, iso-, and s-C4H9MgBr were also investigated in toluene at −78°C. With an increase in the bulkiness of the alkyl group the isotacticity of the polymer increased and the molecular weight distribution became narrower. The addition of MgBr2 also increased the isotacticity of the polymer. The results of block copolymerizations of MMA and MMA-d8 or ethyl methacrylate are also described.

Highly transparent and conducting polypyrrole-poly(vinyl alcohol) composite films prepared by gas state polymerization.

Abstract: Highly Transparent and Conducting Polypyrrole–Poly(vinyl alcohol) Composite Films Prepared by Gas State Polymerization

Ionic conductivity of network polymers from poly(ethylene oxide) containing lithium perchlorate.

Abstract: The structure-conductivity relationships were investigated on the network polymers from poly(ethylene oxide)(PEO) containing lithium perchlorate (LiClO4), in contrast to the polymer complex formed by linear PEO and LiClO4. The crosslinked structure caused a considerable decrease in the degree of the crystallinity of the resulting PEO–LiClO4 complexes, which contributed to high ionic conductivity. Li+ ions were demonstrated as mobile species in these polymer complexes, while ClO4− ions contributed somewhat to ionic conductivity. The high ionic conductivity of the order of 10−5 Scm1 at 30°C was attained by a crosslinked PEO–LiClO4 complex of [LiClO4]/[EO unit] =0.02.

Molecular Weight Dependence on the Morphological Properties of Polyethylene Gels

Abstract: Polyethylene gels were prepared by gelation/crystallization from dilute decalin solutions using five kinds of polyethylenes with different molecular weights and degrees of branching. The decalin was allowed to evaporate from the gels under ambient condition in order to prepare dry gels. The dry gel of ultra-high molecular weight polyethylene (UHMWP) of Mw=6×106 forms a film but the other low molecular weight polyethylenes (LMWP) with molecular weight lower than 3×105 do not form a film. In order to investigate such a difference, the morphological properties of five kinds of dry gels were investigated by scanning electron microscopy, polarized microscopy, small angle light scattering, and small angle X-ray scattering. Within LMWP dry gels, observation reveals spherulitic textures whose crystal lamellae are rotated around a radial direction. In contrast, within the dry gels of UHMWP, there exists rodlike textures as assemblies of large lamellar crystals which are highly oriented with their flat faces parallel to the film surface. To assure ultradrawing up to consistently high draw ratio, a suitable number of entanglements should be formed by tie molecules which connect the crystal lamellae.

Apparatus to measure small-angle light scattering profiles of polymers under shear flow.

Abstract: The apparatus and the principle to measure flow small-angle light scattering (“flow-SALS”) are presented as one of the rheo-optical techniques. The flow-SALS technique presented here enables one to investigate small-angle light scattering profiles and rheological properties of polymer solutions, liquids, and mixtures, as well as polymer liquid crystals under various types of shearing, i.e., steady-state shear flow, oscillatory shear flow, and shear recovery after the cessation of steady-state flow. This technique may be useful to investigate the flow-induced formation, dissolution, and deformation of supermolecular structure with spatial correlation length of a few microns, and also their effect on rheological properties. In order to demonstrate the prospect of its use, some preliminary results on flow-SALS from the lyotropic polymer liquid crystal [20 wt% poly(γ-methyl-d-glutamate) in m-cresol] are presented.

UCST and LCST Behavior in Polymer Blends and Its Thermodynamic Interpretation

Abstract: A pair of dissimilar polymers with high molecular weights, poly(acrylonitrile-co-styrene) poly(acrylonitrile-co-butadiene), was found to exhibit both UCST (upper critical solution temperature) and LCST (lower critical solution temperature) behavior. This phase behavior is interpreted by combining the solubility parameter theory involving the free volume term and the recent idea of “miscibility window” for the polymer blends including random copolymers.

Dynamic Mechanical Absorptions Observed for Regenerated Cellulose Solids in the Temperature Range from 280 to 600 K

Abstract: An attempt was made to establish the mechanism of the dynamic mechanical absorption phenomena of regenerated cellulose solids observed in the temperature range between 280 and 600 K at a frequency of 110 Hz. For the purpose, isochronal dynamic viscoelasticities of regenerated cellulose fibers and membranes were measured by dynamic modulus, loss modulus, and dynamic loss tangent in air at a heating rate of 12 K min−1 or in various kinds of liquid medium at 3 K min−1. Three absorption peaks, α1, α2, and αH2O, and one absorption shoulder, αsh, were observed near 573, 513, 303, and 393 K, respectively. The content of water absorbed in the sample was closely related to the appearance of the αH2O absorption which was due to the cooperative motion of polymer segment and absorbed water molecules. The dependence of the viscoelasticity on temperature and frequency revealed that the α2 absorption consisted of two αa absorptions, α2,1 and α2,2, whose apparent activation energies were 289 and 209 kJmol−1, respectively. All of the α1, α2,1, α2,2, and αsh absorptions originated from the micro-Brownian motion of polymer segments in the amorphous region. The temperatures of these four absorptions were dominated by the segmental environment such as the density of intermolecular hydrogen bonding.

Studies on p - and m -Vinylbenzylmagnesium Chlorides as Initiators and Monomers—Preparations of Macromers and Poly(Grignard reagent)

Abstract: p- and m-Vinylbenzylmagnesium chlorides (VBzMgCl) were prepared in diethyl ether from the corresponding chloromethylstyrenes, and used as initiators in the polymerizations of MMA and styrene. PMMAs with a variety of tacticities were obtained in toluene and THF by these initiators, and highly syndiotactic (S>96%) PMMA of low polydispersity (Mw/Mn=1.19) could be prepared with m-VBzMgCl in THF at −110°C. It was found by the totally deuterated monomer technique that the polymer molecule thus obtained had one vinylbenzyl group at the beginning of the chain (α-end). The PMMAs could be used as macromers, which were polymerized and copolymerized with styrene by a radical initiator. p-VBzMgCl polymerized styrene in THF at 0°C, and the resulting polystyrene can also be used as a macromer. m-VBzMgCl and benzylmagnesium chloride did not give polystyrene. Spontaneous polymerizations of VBzMgCls to poly(Grignard reagent)s were also studied.

Ultradrawing of isotactic polypropylene films produced by gelation/crystallization from solutions.

Abstract: Films of ultra-high molecular weight isotactic polypropylene (4.4×106) were produced by gelation/crystallization from dilute solutions according to the method of Smith and Lemstra. The dried gel films could be readily stretched to a maximum draw ratio of 100 in a hot oven at 165—17 °C. For a draw ratio of 100, tensile strength and the Young’s modulus attained the maximum values of 1.56 and 40.4 GPa, respectively, at 20°C. These values are among the highest reported for polypropylene. The tensile strength was beyond the theoretical value reported by Samuels and the Young’s modulus is close to the theoretical value measured by X-ray diffraction.

Studies on the Radical Polymerization of Methyl Methacrylate in Bulk and in Benzene Using Totally Deuterated Monomer Technique

Abstract: Studies on the Radical Polymerization of Methyl Methacrylate in Bulk and in Benzene Using Totally Deuterated Monomer Technique

Structure and properties of fatigued segmented poly (urethaneurea) s. I: Segment orientation mechanism due to fatigue

Abstract: Structure and Properties of Fatigued Segmented Poly(urethaneurea) I. Segment Orientation Mechanism due to Fatigue

Linear Viscoelastic Properties of Polybutadiene. A Comparison with Molecular Theories

Abstract: The linear viscoelastic properties of a series of linear entangled polybutadienes were studied. It is found that the melt viscosity ηo∝M3.38 and the plateau modulus GNo∝Mo. The zero-shear recoverable compliance Jeo decreases slightly with increasing MW above 40,000. One high MW polybutadiene was diluted with a low MW (≍1800) polybutadiene. For these mixtures it is found that ηo∝φ3.35 and GNo∝φ2, where φ is the volume fraction of the high MW component. Jeo of the mixtures depends somewhat more strongly on φ than according to φ−2. Both the MW and φ dependence of ηo and Jeo are in agreement with Doi’s modification of the reptation model that includes contour-length fluctuations. Experimental values of Jeo are in quantitative agreement with the theory. The experimental loss (G″), and storage (G′) moduli-frequency curves can be fitted with a high degree of precision to Doi’s theory.

An Odd–Even Effect in the Mesophasic Behavior of Dimer Liquid Crystals Due to the Bond Orientation of a Phenylene Unit Incorporated in the Flexible Spacer

Abstract: An Odd–Even Effect in the Mesophasic Behavior of Dimer Liquid Crystals Due to the Bond Orientation of a Phenylene Unit Incorporated in the Flexible Spacer

Dielectric and Piezoelectric Properties of Nylon 9 and Nylon 11

Abstract: Various specimens of nylon 9 and nylon 11 were prepared, and their crystalline structures, the temperature and frequency dependences of electric properties were investigated. Dielectric constants (at 10 Hz).of various specimens were about 2.5—3 in the temperature range from −160°C to room temperature, and they began to increase near Tg and reached above 30 at about 100°C. They showed three dielectric loss peaks due to two types of local mode motion and the glass transition. Piezoelectric behavior of the α form specimen obtained by slow cooling of melts and that of the γ form specimen obtained by casting from its trifluoroacetic acid solution were almost the same, but a mixture of α and γ forms obtained by quenching of the melts into liquid nitrogen had a larger piezoelectric constant than the above two. From these results it may be considered that the lower regularity in the dipole orientation within the mixture makes it relatively easier to rearrange the dipoles in parallel to the electric field in the poling process. Nylon 9 had a larger piezoelectric constant than nylon 11, which may be due to the higher dipole density of nylon 9. The piezoelectric stress constant of the stretched film was larger than the unstretched one, but the piezoelectric strain constant of both were similar. The largest piezoelectric stress constant of 2.1 mCm−2 (at 25°C) was obtained from a stretched nylon 9 specimen and the largest piezoelectric strain constant of 1.1 pCN−1 (at 25°C) was obtained for nylon 9 specimen which was a mixture of α and γ forms.

Preparation and characterization of poly(2-vinylpyridine)s with narrow molecular weight distributions.

Abstract: Anionic polymerization of 2-vinylpyridine was carried out in tetrahydrofuran at −78-°C with four kinds of initiators, i.e., n-butyllithium, tritylsodium, cumylpotassium and cumylcesium. It was confirmed that the polymerizations with all these initiators proceeded on a living mechanism and the polymers obtained had narrow molecular weight distributions. The triad isotactic contents of the polymers prepared were almost identical, independently of counter ions. The intrinsic viscosity-molecular weight relationships were determined in two good solvents and in a θ-solvent From those relationships, it was concluded that poly(2-vinylpyridine) has almost the same chain flexibility as ordinary vinyl polymers.

Polymerization by Phase Transfer Catalysis IV. Polythiocarbonates by Polymerization of Diphenols with Thiophosgene

Abstract: Polymerization by Phase Transfer Catalysis IV. Polythiocarbonates by Polymerization of Diphenols with Thiophosgene

Thermotropic Main Chain Polyesters with Polymethylene Spacers and Their Low Molecular Weight Model Compounds—Odd-Even Effect of Polymethylene Spacers

Abstract: A series of main-chain thermotropic polyesters which have an alternating sequence of mesogenic units and polymethylene spacers as well as their model compounds with two terminal mesogenic units and central spacers were prepared. Their liquid crystalline behavior, especially their thermal transition properties and nature of mesophases were compared with each other. The polymers and the low molecular weight model compounds exhibited in their transition temperatures distinctive odd-even dependence on the number of methylene units in the spacer. All of them formed nematic mesophases in melts. The liquid crystalline properties of the polymers and the model compounds were studied by differential scanning calorimetry and on the hot-stage of a polarizing microscope.

The Role of p -Oligosiloxane Substituents of Polystyrene in Selective Oxygen Permeation through the Polymer Film

Abstract: Selective oxygen permeation through the films of p-(oligosiloxanylstyrene) was investigated, and the role of the oligosiloxane substituents is discussed based on a dissolution-diffusion mechanism. The oligosiloxane side chains were found to play an important role to enhance the diffusion of oxygen.

Rheology, DSC and Volume or Weight Change Induced by Immersion in Solvents for Agarose and Kappa-Carrageenan Gels

Abstract: In order to study the gelling ability of kappa-carrageenan and agarose, measurements of dynamic viscoelasticity, differential scanning calorimetry (DSC) and volume or weight change induced by immersion in organic solvents have been made at the range of concentration from 2 to 8% (w/w). The results obtained are as follows; (1) The value of dynamic Young’s modulus E′ for agarose gels increases with increasing temperature up to about 35°C, while it decreases rapidly with increasing temperature above about 35°C. On the other hand, the value of E′ for kappa-carrageenan gels decreases with increasing temperature. (2) DSC curves show one endothermic peak which is caused by the melting of gels. The temperature of the endothermic peak accompanying the melting of agarose gels is independent of concentrations, and that of carrageenan gels shifts to higher temperatures with increasing concentrations. (3) The weight or volume change by immersion in dimethyl sulfoxide (DMSO)–water or in ethanol is far more remarkable in kappa-carrageenan gels than in agarose gels. The difference of these kinds of behaviour between agarose and kappa-carrageenan gels is understood mainly by the quantity and position of sulfate side groups in molecules.

Further Study on the Distribution of Substituent Group in Cellulose Acetate by 13C{1H}NMR Analysis: Assignment of Carbonyl Carbon Peaks

Abstract: An attempt was made to determine an unsolved problem in peak assignment of carbonyl carbon region in 13C NMR spectra for cellulose acetate. For this purpose, Kamide and Okajima’s method for determination of the distribution of acetyl group among three hydroxyl groups in a glucopyranose unit was reexamined carefully using a 200 MHz FT-NMR spectrometer, adequate and the most reasonable assignment at present was made on the carbonyl carbon peaks in NMR spectra, applying a low-power selective decoupling method to acetyl methyl proton located at specific carbon position. All three NMR peaks in the carbonyl carbon region were assigned to be attributed to the acetyl groups located at C6, C3, and C2 positions, from the low magnetic field side. The previous Kamide and Okajima’s assignment on C3 and C2 peaks was found to be erroneoulsy made by neglecting an overlapping of the three peaks due to low resolving power in the 1H and 13C NMR spectrometer used by them. The new and complete assignments were in good agreement with those by Miyamoto et al. The method of Miyamoto et al. was examined in detail in the light of the validity of the assignment of carbonyl carbon peaks for not fully substituted cellulose acetate.

Studies of styrene and 2-vinylpyridine block copolymers; Preparation and characterization.

Abstract: Preparation of di- and triblock copolymers of styrene-h8, styrene-d8, and 2- vinylpyridine by anionic polymerization was carried out for the purpose of obtaining block copolymer samples containing a poly(styrene-d8) part and having well defined molecular characteristics. The block copolymerization proceeded successfully when the polymerization was carried out in the order of styrene-h8, styrene-d8, and 2-vinylpyridine or of styrene-d8, styrene-h8, and 2-vinylpyridine, whereas it was not successful when the polymerization was started from 2-vinylpyridine. All block copolymer samples polymerized in the order of styrene and 2-vinylpyridine were found to have narrow molecular weight distributions with respect to each component.

Enhanced oxygen permeation through surface modified blend films containing polydimethylsiloxane graft copolymers.

Abstract: Enhanced Oxygen Permeation through Surface Modified Blend Films Containing Polydimethylsiloxane Graft Copolymers

Proton Spin Lattice Relaxation in Vinylidene Fluoride/Trifluoroethylene Copolymer I. Vinylidene Fluoride 72 mol% Copolymer

Abstract: The proton spin lattice relaxation times T1 of drawn films of a VDF/TrFE copolymer (VDF 72 mol%) were measured for various values of γ, which was the angle between the magnetic field and the draw direction of the film, and for different Larmor frequencies ω, over a temperature range from −23 to 130°C. Three kinds of T1 relaxation processes were observed below the Curie temperature (Tc), around Tc, and at a certain temperature in the paraelectric phase. The curve of ln T1 against reciprocal temperature 1/T was linear for the relaxation process in the paraelectric phase. The T1 became larger as the frequency ω and the angle γ increased.The formulation of T1 in the paraelectric phase for the oriented copolymer was derived, using the non-exponential correlation function which describes a one dimensional diffusion motion of conformational defects along the chain. The existence of the 1-D diffusion motion of the conformation defect was confirmed by a reasonable agreement between the theoretical and experimental results.

Effects of the Degree of Hydration of Water Swollen Poly(vinyl alcohol) Films on Their Iodine Complexation

Abstract: PVA films with a wide span of hydration (swelling) were soaked at different temperatures in iodine aqueous solutions to make the iodine–PVA complex, with a particular concern for the effects of the degree of hydration (D.H.) on the complex formation. The visible absorption maximum λmax increased with D.H., while it decreased with temperature. The equilibrium amount of the complex increased with D.H. at a given concentration of iodine below 20-°C. However, the effects of D. H. on the amount of complex deteriorated with increasing temperature and at 45-°C became reversed to those at low temperature. When the samples soaked at 5-°C were heated in the solution, the amount of complex suddenly began to decrease at 20-°C; this corresponded to the sudden stress relaxation of water swollen PVA films. This transition seems to have great effect on the complexation.

Glass transition temperatures in polymer mixtures

Abstract: A fluid-lattice theory of fluid mixtures is combined with the Gibbs-DiMarzio approach of zero configurational entropy at glass transition in order to correlate and predict the composition dependence of glass transition temperature, Tg, in one-phase polymer mixtures. Such a combination allows an independent quantitative estimation of the significance to Tg of both equation-of-state terms and chain flexibility terms. The model is tested against experimental data on Tg’s for three polymer mixtures known to be compatible in the complete range of composition. The effect of the various binary parameters on glass transition is discussed along with the effect of chain flexibility change upon mixing. It is shown that chain flexibility terms are predominant in determining Tg. Two possible ways of taking into account chain flexibility change are proposed.

The sol-gel transition and the liquid-liquid phase separation in poly (vinyl chloride) solutions

Abstract: The dynamics of the sol-gel transition in poly(vinyl chloride) γ-butyrolactone system was investigated by light scattering. The dynamical studies confirmed that this system has an UCST (upper critical solution temperature). In the phase diagram, temperature vs. concentration, the spinodal curve crosses the sol-gel transition curve. This situation has been predicted by Coniglio et al. as a result of the site-bond correlated-percolation problem. The gelation takes place both above and under the spinodal curve, suggesting two modes of gelation: one is accompanied by a spinodal decomposition and the other takes place without liquid-liquid phase separation. In the former case, the dynamics of phase separation at an early stage of gelation is well described within the framework of Cahn’s linearized spinodal decomposition theory. It is noted that, in order to understand the entire mechanism of sol-gel transition, one should clarify the three dynamical aspects on the liquid-liquid phase separation, percolation-type association, and liquid-solid transition.

Liquid-Liquid Phase Separation and Gelation in the Poly(vinyl alcohol)-Poly(ethylene glycol)–Water System. Dependence on Molecular Weight of Poly(ethylene glycol)

Abstract: Liquid-Liquid Phase Separation and Gelation in the Poly(vinyl alcohol)-Poly(ethylene glycol)–Water System. Dependence on Molecular Weight of Poly(ethylene glycol)

Poly[oligo(oxyethylene) methacrylate-co-sodium methacrylate] as a Polymeric Solid Electrolyte with Sodium Ionic Conduction

Abstract: Poly[oligo(oxyethylene) methacrylate- co -sodium methacrylate] as a Polymeric Solid Electrolyte with Sodium Ionic Conduction

Studies on the polymerization of methyl methacrylate with butylmagnesium chloride by the aid of totally deuterated monomer ― structures of polymerization products and fate of initiator

Abstract: Totally deuterated methyl methacrylate (MMA-d8) was polymerized by C4H9MgCl in toluene at −78°C, and the resulting polymer and oligomer were analyzed by 1H NMR spectroscopy. The polymer and oligomer was found to contain butyl pentadeuteroisopropenyl ketone (BIPK-d5) units. The ketone was formed by the addition of the initiator onto the carbonyl group of the monomer. The content of BIPK-d5 units in the polymer and oligomer was found to be 0.3 and 0.4 per chain, respectively. FD- and EI-mass spectra of the fractionated oligo(MMA)s indicated that most of the BIPK units were located at their terminating chain ends. Structures which were produced by intramolecular cyclization and by carbonyl addition of propagating anions onto MMA or BIPK were found at the end of the oligomer chain, but the amounts of these structures were at most 10% of the chain. The fate of the initiator during the polymerization was clarified for the most part. From the results, the mechanism of polymerization is discussed in some detail.