Showing papers in "Polymer Journal in 1982"

Statistical Thermodynamics of r -Mer Fluids and Their Mixtures

Abstract: A modified fluid-lattice theory of fluids considering a finite quasi-lattice coordination number and a constant lattice site volume for all r-mers is developed. The theory is tested against experimental information on specific volumes, vapor pressures, orthobaric densities and heats of vaporization of pure components. Some common polymers and some typical polymer solvents have been chosen for testing the theory. The theoretical treatment has been extended to mixtures and tested against experimental data on volumes of mixing, heats of mixing, and χ interaction parameters of polymer solutions. Results have been compared with those obtained with a two-parameter new Flory theory and with the three-parameter new Huggins theory. Both for pure components and for mixtures, the effect of introducing a non-random quasi-chemical correction is discussed.

Excluded-Volume Effects in Dilute Polymer Solutions. XIII. Effects of Chain Stiffness

Abstract: The chain length dependence of mean-square radius of gyration ‹S2› for several polymers, stiff or flexible, in dilute solution is compared with that for the Kratky–Porod (KP) wormlike chain, using representative literature data. In the region of nK, the number of Kuhn’s statistical segments, below about 50, ‹S2› for all polymers examined is accurately described by Benoit–Doty’s expression for the KP chain. Upward deviations from this expression occur at nK of about 50, regardless of the chain stiffness. Thus, the critical chain length Lc for the onset of excluded-volume effect on the average dimensions of a polymer is approximately proportional to q, the persistence length of the polymer, with a proportionality factor of about 100. The value of Lc estimated from this relation is at least one order of magnitude larger than that predicted theoretically by Yamakawa and Stockmayer.

Liquid Crystal Polymers. V. Thermotropic Polyesters with Either Dyad or Triad Aromatic Ester Mesogenic Units and Flexible Polymethylene Spacers in the Main Chain

Abstract: The thermal properties of two new series of thermotropic, liquid crystalline polyesters were studied by differential scanning calorimetry and on a hot-stage of a polarizing microscope. The first series contained an aromatic ester triad with a central terephthaloyl and two terminal oxybenzoyl units connected by a flexible polymethylene spacer containing from two to ten methylene units. The second series contained a head-to-head tail-to-tail aromatic ester dyad with one terephthaloyl and one oxybenzoyl unit and either a dimethylene or hexamethylene spacer. The melting temperatures and the transition temperatures for conversion from the mesophase to the isotropic phase (the clearing temperature) of the polyesters in the first series initially decreased in a zig-zag manner for polymers with up to nine methylene units but increased for the decamethylene polymer. The temperature ranges over which the mesophase formation occurred were generally broader for polymers containing an odd number of methylene units than for those with an even number of units. Most, if not all, of the polymers in both series formed nematic states on melting. The enthalpy and entropy changes for the clearing transition both increased with the length of the polymethylene spacer. Polymers of the second series possessed lower transition temperatures and narrower temperature ranges for mesophase formation, as would be expected for the shorter mesogenic unit.

Volume and enthalpy relaxation in polystyrene.

Abstract: A study was carried out on the effects of thermal aging on specific volume V and specific enthalpy H of polystyrene below the glass transition temperature. The dependence of V and H on annealing time was similar. No significant effect of the distribution of molecular weight on the relaxation behavior was found. The behavior of V and H reaching a maximum after a double-step temperature-jump was also investigated. The time for the maximum V and H varied in proportion to the period of pre-annealing. The time for the maximum volume was slightly longer than that for the maximum enthalpy. These facts indicate that the dependence of V and H on the order parameters specifying the glassy state are similar but not exactly the same. From the enthalpy and volume relaxation curves, the enthalpy required for creating free volumes in polystyrene was calculated to be 2.0 kJ cm−3. The behavior of the volume relaxation was discussed by assuming a wide distribution of relaxation time.

Study on Polysaccharide by the Fluorescence Method. II. Micro-Brownian Motion and Conformational Change of Amylose in Aqueous Solution

Abstract: The segmental motion of amylose in aqueous solution and the conformational transition with temperature and pH were studied by the fluorescence polarization method. We prepared two types of fluorescent conjugates of amylose: amylose conjugated with fluorescein randomly throughout chain (F-Amylose) and amylose conjugated locally on a terminal segment (t-F-Amylose). The value of the rotational relaxation time for t-F-Amylose was much smaller than that for F-Amylose. This result suggests that a terminal segment undergoes a more rapid micro-Brownian motion than interior segments. Polarization curves of these conjugates gradually departed from the Perrin equation when the temperature was raised. F-Amylose showed a gradual departure above 45°C but t-F-Amylose showed a departure at room temperature. This indicates that the conformational transition occurs first in terminal segments and then extends to the interior segments with increasing temperature. The effect of pH on the polarization was also examined. When measured as a function of pH, fluorescence depolarization increased pronouncedly in the alkaline region. In contrast to changing temperature, depolarization began to increase at the same pH for the two amylose conjugates.

Thermal Behavior of n-Alkanes from n-C32H66 to n-C80H162, Synthesized with Attention Paid to High Purity

Abstract: The general principle for synthesizing higher n-alkanes of the highest purity is described briefly. Thermal behavior of the synthesized n-alkanes from n-C32H66 to n-C80H162 were examined by means of DSC, small- and wide-angle X-ray scattering and optical microscopy. All the crystalline n-alkanes except for n-C80H162, when crystallized from solution, showed transitions to high-temperature monoclinic modifications (Mh01, h=1 or 2) before the rotator transition or the melting, irrespective of the number of carbon atoms (n) being odd or even and the difference in room-temperature modifications of even n-alkane. One feature of the transition was its irreversibility. The odd n-alkanes of n-C33H68, n-C37H76, and n-C45H92 showed also another type of solid-solid transition below the transition mentioned above. Both types of the transitions were thermally proved to be of the first-order. Although no simple functional forms were generally given to the relationships between the transition temperature and n, the temperatures for the transition of orthorhombic higher n-alkanes to the Mh01 phase increased with n, reaching about 90°C for n-C69H140. The transition to Mh01 was accompanied by a morphological change on the crystal surface, in the form of characteristic striations parallel to the bs subcell axis. This suggests that the solid-solid transition proceeds successively from a nucleating site with a staggering of molecules in the chain direction. If the slow rate of the process and complicated behavior of the Mh01 phase are taken into account, the kinetical view point of the phase transition leads to the working hypothesis that the molecular motion of the long chains in the n-alkane crystals, which consists of rotational and longitudinal motions or a flip-flop motion, takes place only in this transformation process.

Phase Separation Process in Polymer Systems. I. Light Scattering Studies on a Polystyrene and Poly(methylphenylsiloxane) Mixture

Abstract: Early stages of phase separation in liquid mixtures of polystyrene (PS) and poly(methylphenylsiloxane) were studied by light scattering. Measurements were made at four concentrations less than 60 wt% PS and at several temperatures in the two-phase region. The time (t) dependence of maximum intensity of scattered light Im and the corresponding wave number km did not obey the Cahn theory but could be represented by power-laws: Im∝tθ and km∝tφ with θ=0.69 (±0.17) and φ=−0.29 (±0.05). These values of θ and φ agree well with those predicted by recent theories of Langer et al. and Binder et al. for spinodal decomposition, and also with the experimental values for binary mixtures of small molecules. It was concluded that there is no essential difference in the mechanism of phase separation between mixtures of small molecules and polymer blends.

Polymerization of Methylpentynes by Transition Metal Catalysts: Monomer Structure, Reactivity, and Polymer Properties

Abstract: Polymerization of Methylpentynes by Transition Metal Catalysts: Monomer Structure, Reactivity, and Polymer Properties

Studies on Chitin. VI. Preparation and Properties of Alkyl-Chitin Fibers

Abstract: Alkali-chitin was prepared by a simple procedure which included a freezing process in a sodium hydroxide-sodium dodecylsulfate system. Its alkylations were achieved with various alkyl halides of different chain lengths and bulkiness. The affinity toward water or formic acid was remarkably enhanced by the alkylations in spite of the low degree of substitution. The increase in hydrophilicity was considered to be result from the partial destruction of crystalline structure in the chitin molecule. The alkyl-chitin fibers were successfully prepared by spinning the solution of alkyl-chitin in formic acid-dichloroacetic acid mixture into ethyl acetate. The extent of swelling with water was found to correspond both to the chain length and the bulkiness of the alkyl group. The hydroxyl group at the C6 position is considered to be substituted prior to that of C3 position, according to a 13C NMR study. 1H NMR and elemental analysis proved useful in estimting the degree of alkylation even in the case of low degree of substitution.

Melting and transformation behavior of .GAMMA. form nylon 6 under high pressure.

Abstract: Thermal behavior under high pressure of the γ form nylon 6 obtained by iodine treatment was investigated by means of a high pressure differential thermal analysis. The crystalline structures which resulted in the endo- and exo-thermic peaks in the thermogram were examined with the wide angle X-ray diffraction measurement. Under relatively low pressure (170—2000 kg cm−2), two endothermic peaks were found. With increasing pressure, the lower temperature side endotherm due to the melting of the γ form crystal became small, while the higher one due to the melting of the converted a form crystal became large. Under high pressure (above 2000 kg cm−2) an endotherm due to the melting of the converted α form crystal and an exotherm were observed. This exotherm is attributed to the γ to α form transformation. In this case, the transformation occurred without melting the γ form crystal, in contrast to the situation at atmospheric pressure. The pressure dependences of the melting peak temperatures of the α form and the γ form were almost the same and equal to 18°C per 1000 kg cm−2.

Dynamic viscoelastic properties of ABS polymers in the molten state IV. Effect of rubber particle size.

Abstract: Dynamic viscoelastic behavior of molten ABS polymers in which dispersed rubber particles are narrow in size distribution and hardly agglomerate were investigated as a function of the rubber content and the rubber particle size over wide ranges of temperature and frequency. The relaxation of the matrix AS copolymer associated with chain entanglement shifted the relaxation spectra of ABS to a longer time in proportion to the volume fraction of the dispersed phase. On the other hand, the long time relaxation spectra associated with particle-particle interactions depended strongly on both rubber content and particle size. With an increase in the rubber content and also a decrease in the rubber particle size, the spectra became higher. This may be explained as a result of a decrease in the surface distance between neighboring rubber particles.

Separation of Benzene–Cyclohexane Azeotropic Mixture through Polymeric Membranes with Microphase Separated Structures

Abstract: Separation of Benzene–Cyclohexane Azeotropic Mixture through Polymeric Membranes with Microphase Separated Structures

Molecular Aggregation and Gelation in Poly(y-benzyl L -glutamate) Solutions

Abstract: Poly(γ-benzyl L-glutamate) forms a thermoreversible gel in benzyl alcohol. The network comprises fairly crystalline fibrillar aggregates. There are two types of complex structures depending on the gelation temperature, in which the interchain distances are independent of concentration and the volume fraction of polymer is roughly 0.77. The two complexes have different melting points in the range of 60—70°C, which are almost constant over a wide range of concentration. The gel rigidity depends on polymer concentration and molecular weight in the following way. There is a critical concentration, Co, around 0.5 wt%. For C>C0, the shear modulus is proportional to C1.3 and independent of molecular weight. For C

Ionic conductivity of polymeric solid electrolytes based on poly(propylene oxide) or poly(tetramethylene oxide).

Abstract: Ionic Conductivity of Polymeric Solid Electrolytes Based on Poly(propylene oxide) or Poly(tetramethylene oxide)

Phase Separation Process in Polymer Systems III. Spinodal Decomposition in the Critical Mixture of Polystyrene and Poly(methylphenylsiloxane) and Scaling Analysis

Abstract: Phase Separation Process in Polymer Systems III. Spinodal Decomposition in the Critical Mixture of Polystyrene and Poly(methylphenylsiloxane) and Scaling Analysis

Structural Changes during Mechanical Mixing in Carbon Black-Natural Rubber Systems Studied by Pulsed NMR

Abstract: Structural Changes during Mechanical Mixing in Carbon Black-Natural Rubber Systems Studied by Pulsed NMR

Relaxation Spectroscopy of the Dielectric β-Relaxation in Poly( n -alkyl methacrylate)s by Absorption–Current Measurements. I. Dielectric Relaxation Spectra for Atactic Polymers

Abstract: Relaxation Spectroscopy of the Dielectric β-Relaxation in Poly( n -alkyl methacrylate)s by Absorption–Current Measurements. I. Dielectric Relaxation Spectra for Atactic Polymers

Electron Exchange Phenomena of Polymers Containing Nitroxyl Radicals

Abstract: The influence of electron exchange on the physical properties of polymers containing nitroxyl radical in their side chains has been studied by ESR, magnetic susceptibility measurement and cyclic voltammetry. ESR study shows that the electron exchange interaction between free radicals bound to a polymer chain is more effective than that between the corresponding monomeric radicals. Magnetic susceptibility (XM) was measured at temperatures between 4K and 273 K. The values of XM for the polymers obey the Curie-Weise Law (XM=c/(T−θ)), where magnetic moments obtained from XM show the presence of antiferromagnetic interaction between the nitroxyls of a polymer chain, although the interaction is not large enough to bring about long range ordering in the spin orientation of the nitroxyls. In the corresponding monomers, no antiferromagnetic interaction was observed. Cyclic voltammetry in DMF shows that the electrode process in polymer system is a reversible multiple-electron transfer reaction, where the number of the transfer (np) is 60% of the total free radicals per molecule. A comparison of the shape of the voltammetric response curve in the polymers with that in the corresponding monomers suggests that the interaction between nitroxyl radicals in the polymer is too weak to be reflected in electrochemical behavior.

Synthesis of amphiphilic graftcopolymers from polystyrene macromonomer.

Abstract: Graftcopolymers of well-defined structure and composition were prepared by the radical copolymerization of polystyrene macromonomers with functional comonomers. The macromonomer was prepared by the polymerization of styrene in the presence of monoiodoacetic acid as a chain transfer agent, followed by an end-capping reaction with glycidyl methacrylate. In the case of 2-hydroxyethyl methacrylate as a comonomer, hydrophilic graftcopolymer soluble in polar solvent was obtained and characterized by thin layer chromatography. In the case of perfluoroalkyl acrylate as a comonomer, hydrophobic graftcopolymer soluble in ordinary solvent was obtained.

Isotropic-Liquid Crystal Phase Equilibrium in Aqueous Solutions of a Triple-Helical Polysaccharide Schizophyllan

Abstract: A polysaccharide schizophyllan known to have a rodlike shape in solution was investigated. The system schizophyllan + water exhibited an equilibrium between isotropic and cholesteric phases. The temperature-concentration phase diagram in a temperature range 5—80°C and a concentration range 0—38.8 polymer wt% was determined. The phase diagram determined is characterized by a narrow biphasic region separating the isotropic phase from the cholesteric phase and resembles those reported by Miller and coworkers for polypeptide solutions, except that it has no broad biphasic region at low temperature. The experimental results for schizophyllan appear to favor the Flory–Ronca theory of rodlike molecules, but the data are not sufficiently detailed to draw definite conclusions.

Phase Separation Process in Polymer Systems. II. Microscopic Studies on a Polystyrene and Diisodecyl Phthalate Mixture

Abstract: Late stages of phase separation in liquid mixtures of polystyrene (PS) and diisodecyl phthalate were investigated by microscopic observation. Droplet structures were observed in the matrix. Average droplet diameters d for mixtures of 5.7 and 16.6 wt% PS varied with the period of phase separation t according to a power-law, d∝tφ, with φ=0.30 (±0.09) being independent of quench depth. This value of φ agreed well with 1/3, theoretically predicted on the basis of the coalescence mechanism and the Ostwald Ripening mechanism. For a blend of PS and poly(methylphenylsiloxane), we investigated the relation between the average droplet diameter and the wave length at the maximum intensity of scattered light observed in the early stage.

Polymerization of t-Butylacetylene by Group 6 Transition Metal Catalysts: Geometric Structure Control by Reaction Conditions

Abstract: The geometric structure of poly(t-butylacetylene) could be controlled by the choice of suitable polymerization conditions (solvents and catalysts): t-Butylacetylene was polymerized in high yield by MoCl5 and WCl6 in oxygen- or nitrogen-containing solvents (e.g., anisole, acetophenone, benzonitrile and nitrobenzene). The molecular weights of the polymers formed were as high as 5×104—2×105. According to 13C NMR, polymers prepared in nonpolar solvents like toluene comprised comparable amounts of cis and trans structures. On the other hand, polymers obtained with MoCl5 in oxygen- or nitrogen-containing solvents possessed the cis structure exclusively. The mechanism of geometric structure control was discussed.

Urethane Substituted Polydiacetylene: Synthesis and Characterization of Poly[4,6-decadiyn-1,10-diol-bis( n -butoxy-carbonyl-methyl-urethane)]

Abstract: Urethane Substituted Polydiacetylene: Synthesis and Characterization of Poly[4,6-decadiyn-1,10-diol-bis( n -butoxy-carbonyl-methyl-urethane)]

X-Ray Study of Thermal Expansion and Transition of Crystalline Cellulose

Abstract: For the cellulose crystals I and II, the spacings and intensities of some typical X-ray reflections were measured over a range of temperature from room temperature to 200°C. The spacing vs. temperature curve for each reflection exhibited a distinct break at about 150°C for Cell I and at about 100°C for Cell II. The thermal expansion coefficients estimated from this curve for the (101) reflection of Cell I were 5.1×10−5 K−1 below 150°C and 1.6×10−4 K−1 above 150°C. The intensity vs. temperature curve for each reflection also exhibited a break at the same temperature as that for the break of the corresponding spacing vs. temperature curve. The reason for the appearance of these breaks is not yet clear.

Thermodynamic and Hydrodynamic Properties of Cellulose Diacetate–Dimethylacetamide Solutions

Abstract: Viscometric and light scattering investigations were carried out on cellulose diacetate (degree of substitution, DS=2.46) in dimethylacetamide (DMAc) at 25°C. The following molecular weight dependence of limiting viscosity number [η], radius of gyration ‹S2›z1/2 and Flory’s viscosity parameter Φ were obtained: [η]=1.34×10−2 Mw0.82 (cm3 g−1), ‹S2›z1/2=0.68×10−8 Mw0.53 (cm), and Φ=5.15×1021 Mw0.23. Draining effect was not negligible for this system. The unperturbed chain dimension A was determined by methods 2B, 2C, 2E, 2F, and 2G proposed previously [K. Kamide and Y. Miyazaki, Polym. J., 10, 409 (1978)]. The A values obtained by methods 2B, 2C, and 2G were in good agreement with each other and the most probable A value was found to be 1.98×10−8 (cm). The variation in [η], ‹S2›z1/2, and A with solvent is discussed in terms of the dielectric constant of the solvent and also the chemical shifts of the O-acetyl methyl and hydroxyl groups.