Showing papers in "Polymer Journal in 1971"

Thermally Stimulated Discharge of Polymer Electrets

Abstract: A special form of depolarization of polymer electrets is described: the thermally stimulated discharge (TSD). After reviewing its principles and exposing its mathematical analysis, results are presented which show that TSD is a powerful method to gain insight into the molecular mechanisms of the electret effect. In fact, TSD reveals all low-frequency molecular motions. It enables one to determine, e.g., the glass-rubber transition of polymers. Its merits are compared with those of isothermal dielectric, and mechanical methods of investigation.

Infrared Spectra of Poly(acetylene)

Abstract: The infrared spectra of poly(acetylene), poly(acetylene-d2), copoly(acety+acetylene-d2), and copoly(acetylene+acetylene-d1+acetylene-d2) prepared by the Ti(OC4H9)4–Al(C2H5)3 system over a wide temperature range (ca. −100 to 180°C) are reported. A tentative assignment of the observed spectra is made on the basis of model structures in which infinite planar chains of all trans, all trans–cisoid, and all cis–transoid configurations are assumed. The spectral data are best interpreted on the basis of an all cis-transoid (or an all trans-cisoid) structure for the polymers prepared at temperatures lower than −78°C, and an all trans structure for the polymers prepared at temperatures higher than 150°C.Simplified calculations of the C-H and C-D out-of-plane deformation frequencies are made for various model chains. It has been concluded from a comparison of the observed and calculated frequencies that the cis-opening of the triple bond occurs in a polymerization reaction with the Ti(OC4H9)4–Al(C2H5)3 catalyst system at low temperatures.

Structural Studies of Polyesters. IV. Molecular and Crystal Structures of Poly(ethylene succinate) and Poly(ethylene oxalate)

Abstract: In the course of structural studies of aliphatic polyesters of the type [–O–(CH2)x–O–CO–(CH2)y–CO–]n, the molecular and crystal structures of polyethylene succinate) (x=2, y=2) and poly(ethylene oxalate) (x=2, y=0) were determined by interpretation of X-ray diffraction patterns and complementary study of infrared spectra.The crystallographic data are:Poly(ethylene succinate); a=7.60 A, b=10.75 A, c (fiber axis)=8.33 A, orthorhombic space group Pbnb-D2h10, four molecular chains pass through the unit cell.Poly(ethylene oxalate); a=6.44 A, b=6.22 A, c (fiber axis)=11.93 A, orthorhombic space group Pbcn-D2h14, two molecular chains pass through the unit cell.The chain conformation of poly(ethylene succinate) is T3GT3G, in which the two C(H2)–C(H2) bonds in the chemical repeating unit are G or G, where T means trans form and G and G are used to discriminate right-handed and left-handed gauche forms, respectively. The chain conformation of poly(ethylene oxalate) is T5GT5G, in which the C(H2)–C(H2) bond is G or G. There are some close similarities between the molecular and crystal structures of poly(ethylene succinate) and poly(ethylene oxalate), and their structures are quite different from polyethylene-like structures for the higher members (x=2, y≥4) of the ethylene glycol series. The high melting points of poly(ethylene succinate) and poly(ethylene oxalate) among the homologous polymers may be related to these molecular and crystal structures.

Piezoelectricity in Polarized Poly(vinylidene fluoride) Films

Abstract: Piezoelectric films of poly(vinylidene fluoride) were prepared by applying a static electric field of about 500 kV/cm to seven-times elongated films at 80°C for a few hours. The tensile stress T produced the polarization P normal to the surface of the film. The real and imaginary components of the complex piezoelectric strainconstant d=d′−id″=P/T were determined at temperatures from −140 to +160°C. The relation between the piezoelectric constant d′ and the angle θ between the direction of stress and the orientation axis is given by d′=d31′cos2θ+d32′sin2θ, where the 1-axis and 2-axis are parallel and perpendicular to the direction of orientation and the 3-axis is normal to the film plane. The values of d31′ and d32′ at room temperature were approximately 6×10−8 and 1.5×10−8 cgs esu, respectively. The piezoelectric dispersions occurred at four temperatures at which the elastic dispersions also took place.

More on the Analysis of Dilute Solution Data: Polystyrenes Prepared Anionically in Tetrahydrofuran

Abstract: Further comments on the analysis of dilute solution data are provided. Light-scattering and intrinsic-viscosity data used for this purpose are those obtained for monodisperse polystyrenes, prepared anionically in tetrahydrofuran, in benzene, toluene, and dichloroethane at 30°C and in cyclohexane at temperatures ranging from 32.2 to 60.1°C. The value of [η]θ/M1/2 is somewhat greater than the corresponding value for Berry’s polystyrenes prepared anionically in benzene, where [η]θ is the intrinsic viscosity at the theta temperature and M is the polymer molecular weight. This suggests that the two types of samples differ in microstructure, though the precise difference is unknown. However, it is shown that the two-parameter relationships established experimentally in the previous papers are well reproduced in the present data. The relationships are different from those determined by Kato, et al., for monodisperse poly(α-methylstyrene) prepared anionically. Since there is shown to be no essential difference between our and their methods of determining mean-square radii, it seems unlikely that the difference is related to measurements and subsequent treatments. It is suggested rather that the problem is related to Kato’s samples.

Stress Relaxation of Polymer Solutions under Large Strain

Abstract: Shear relaxation moduli G(t, s) were measured for various strains s with a relaxometer of the cone-plate type for concentrated solutions of polystyrene in chlorinated biphenyl. The strain was varied from 0.34 to 25 shear units. The time—temperature reduction method was applicable to the shear-dependent relaxation moduli over the temperature range studied (20—50°C) and the shift factor aT was independent of s. When s was very large, logG(t, s) decreased very rapidly with increasing time in two regions of t (two-step relaxation) while logG(t, s) for small s dropped rapidly only at long times (one-step relaxation). The relative rate of decrease of G(t, s) with increasing s was independent of t when t was larger than a certain time, τk. The maximum relaxation time τm was independent of s while the corresponding strength of relaxation Gm was proportional to ID−0.83 when s was large. Here ID is the first invariant of strain.

Light-Scattering Patterns from Collagen Films in Relation to the Texture of a Random Assembly of Anisotropic Rods in Three Dimensions

Abstract: Polarized light scattering from several types of collagen films cast from an acid soluble collagen and solubilized collagens by proteolitic enzyme (except callagenase) and from denatured films under various conditions, was observed under Hv and Vv polarization conditions.The scattering patterns from the collagen films were different from those from spherulitic films of polyalphaolefins. The patterns were analyzed in terms of a three-dimentional random assembly model of anisotropic rods resulting in the following conclusions. The polar angle of orientation of scattering elements with respect to the rod axis ranged from 50 to 70°, depending on the type of collagen film. The value of p, which is defined by (α⊥−αs)/(α||−α⊥), changes from very positive in the air-dried state to less positive, zero, or even slightly negative in the swollen state in saline, also depending on the types of collagen film.On the other hand, the characteristic Hv patterns were diminished in intensity with denaturation while the Vv patterns–as well as the wide angle X-ray diffraction pattern–were not changed to the same extent. This suggests that the light scattering from denatured films arises mainly from correlation in density fluctuations rather than that of orientation of local anisotropy; that is, it is suggested that denaturation causes disintegration of the crystalline superstructure rather than of the crystallites. These crystallites are too small in their correlation distance of the orientation fluctuation to give Hv scattering at such small scattering angles as several degrees only.

13C–{1H} Nuclear Magnetic Resonance Spectroscopy of Poly(methyl methacrylate)

Abstract: The 13C–{1H} high-resolution nuclear magnetic resonance spectra were measured for poly(methyl methacrylate). The spectra clearly split corresponding to dyad, triad, tetrad, and pentad placements. The relative intensity of every peak for the spectrum of a polymer prepared with 9-fluorenyllithium in tetrahydrofuran/toluene (80/20) at −23°C was reasonably interpreted by the Bernoulli trial model.The nuclear Overhauser effect due to total proton decoupling did not affect the relative intensities among the peaks assigned to chemically equivalent carbons except for the difference in stereochemical configuration. This was confirmed by comparison between the relative intensities of the above-mentioned polymer and by comparison between those of 13C–{1H} and of 1H resonance of the polymer.The microtacticity determined by 13C–{1H} spectra of a polymer prepared with 9-fluorenyllithium in tetrahydrofuran/toluene (4/96) was fairly well interpreted by the stereoblend model, but by neither first-order nor second-order Markovian model.

Thermal Study of Blended Systems of Poly(methyl methacrylate) and Poly(vinyl acetate)

Abstract: Heats of solution of blended and non-blended systems of poly(methyl methacrylate) and poly (vinyl acetate) were measured at 28°C. From the difference between them the heat of blending was estimated according to Hess’s law. The absolute value for the blend prepared by freeze drying, which is thought to be molecularly mixed, was smaller than that for the blend, which shows partial phase separation. This unexpected result is explained by the differences of specific heat behaviour between the systems.

Viscoelastk Properties of Polymer Solutions in High-Viscosity Solvents and Limiting High-Frequency Behavior. I. Polystyrene and Poly(α-methylstyreste)

Abstract: Storage (G′) and loss (G″) moduli were measured for dilute solutions of polystyrene (PS) and poly(α-methylstyrene) (PMS) in Aroclor (chlorinated diphenyl) with the modified Birnboim transducer. The molecular weights (M) were 5.1×104, 8.2×104, and 2.67×105 for PS and 3.55×105 and 8.7×105 for PMS, and the ranges of concentration (c) were 1.5×10−2 to 7.6×10−2 g/ml for PS and 1.5×10−2 to 4.6×10−2 for PMS, respectively. The solvent viscosity ηs varied from 5000 to 9.3 poise over the temperature range of 10 to 35°C employed. The frequency range was 0.02 to 630 Hz. The limiting value of the dynamic viscosity at high frequency η∞′ is described by an equation ln(η∞′/ηs)=[η′]∞c over the whole range of concentration, where [η′]∞ is a constant independent of M and is 14.3 and 22.2 ml/g for PS and PMS, respectively. The limiting value of G′ at high frequency is approximately proportional to c. The time–temperature reduction rule was successfully applied to G′ and G″−ωηs and the shapes of frequency dependence curves of the reduced moduli were described well by the theory of Peterlin.

Thermodynamic Studies on the Glass Transition and the Glassy State of Polymers. I. Pressure Dependence of the Glass Transition Temperature and Its Relation to Other Thermodynamic Properties of Polystyrene

Abstract: The pressure dependence of the glass transition temperature, Tg, and the coefficients of thermal expansion, α, and the compressibility, β, of polystyrene were measured. For the same sample, DSC measurement was also carried out, to obtain specific heat, Cp. From the results, it was confirmed that the relation (∂Tg/∂P)≅TVΔα/ΔCp<Δβ/Δα was valid, in accordance with our theory based on a hole model for polymer liquids and glasses with an assumption of iso-configurational entropy at Tg. Changes of specific heats at Tg associated with intrasegmental interactions and inter-segmental ones were calculated separately by the use of the theory, and ΔCpintra=0.041 and ΔCpintra=0.036 cal/gK were obatined.

Excluded-Volume Effect on Dipole Moments of Polymer Chains

Abstract: The excluded-volume effect on dipole moments of linear polymer chains is investigated by the perturbation method. Fixman’s formulation is followed here except for molecular models. In place of the multi-Gaussian-subchain model a more realistic model is adopted. The expansion factor αu for the dipole moment is found, up to the term in z3, to be αu2=1+(C1z+C2z2+C3z3+···)(‹r·u›02/‹r2›0‹u2›0) where r and u are the end-to-end and dipole-moment vectors, αu2=‹u2›/‹u2›0, the averages without and with the subscript 0 refer to those in the presence and in the absence of the excluded volume, and C’s and z are the familiar quantities in the similar expression for the end-to-end distance, αr2=1+C1z+C2z2+C3z3+···. This result strongly suggests αu2−1=(‹r·u›02/‹r2›0‹u2›0)(ατ2−1) An expression for ‹r·u›0 is given on the basis of the rotational-isomeric-state approximation for skeletal-bond rotations. From a structural symmetry consideration it is concluded that ‹r·u›0=0 and hence the excluded volume has no effect on dipole moments for polymers with no distinguishable direction along chain contours.

Pressure–Strain and Pressure–Volume Relationships in the Crystal Lattice of Polyethylene at 293°K

Abstract: Pressure–Strain and Pressure–Volume Relationships in the Crystal Lattice of Polyethylene at 293°K

Stable Conformations of 1,4-Polybutadiene Chains and Their Model Compound Molecules

Abstract: Rotational isomerism in model compounds of cis- and trans-1,4-polybutadienes was studied. Infrared spectra in the region 600–300 cm−1 were measured for cis- and trans-2-butenes, 1-butene, 1-pentene, 1-hexene, cis- and trans-2-pentenes, cis- and trans-4-methyl-2-pentenes, cis- and trans-3-hexene, cis-2-hexene, and 1,5-hexene. Normal frequencies were calculated for the low frequency vibrations of rotational isomers. From changes in the spectra in the gaseous, liquid, and solid states, it was concluded that the cis and skew conformations are stable for C–C bond neighbouring the trans C=C bond, and only the skew conformation is stable for the C–C bond neighbouring the cis C=C bond.The stable conformations of cis- and trans-1,4-polybutadiene chains are discussed, taking into account the infrared spectra of these polymers and the stable conformations of the model compound molecules.

Electron Spin Resonance Study of Polyethylene Irradiated with Ultraviolet Light

Abstract: ESR Spectrum of polyethylene irradiated with ultraviolet light at −196°C was composed of a superposition of two six line spectra, whose total widths were about 155 and 110 gauss, respectively. Free radicals responsible for these two spectra are –CH2–CH–CH2– and –CH2–CH2. The latter radicals were very reactive and abstracted hydrogen atoms from other parts of polymers to produce former radicals. During the warm-up process, a sharp singlet spectrum appeared at about −125°C, which was assigned to acyl radicals . On further warming allylic free radicals were observed at the temperatures above nearly −30°C. An increase of signal intensity was observed during the warm up process.The primary process of photo-induced reactions in UV-irradiated polyethylene at −196°C was thought to be a Norrish-type I reaction of the carbonyl group, and a production mechanism of free radicals is proposed.The absorption spectrum of polyethylene film in O2 showed greater absorbance than that in N2, which could be attributed to the formation of charge-transfer complexes of polyethylene with oxygen molecules. It was also shown that the charge-transfer complexes participated in radical formation. Photo-induced conversions of acyl radicals and peroxy radicals were also reported.

Thermal Conductivity of Cross-linked Polymers

Abstract: Thermal conductivity of cross-linked polymers was studied theoretically. A theory derived from the network model, which consists of thermal conduction through van der Waals and primary bonds, predicts that the thermal conductivity increases with an increasing degree of cross-linking. Calculations for estimating the effect of cross-linking on the thermal conductivity were made for polystyrene and poly(methyl methacrylate). Thermal conduction through the van der Waals and primary bonds was also discussed using the Debye formula for the thermal conductivity of low molecular crystals.

Effects of Catalysts on Dielectric Properties and D. C. Conduction in Poly(ethylene terephthalate)

Abstract: Effects of Catalysts on Dielectric Properties and D. C. Conduction in Poly(ethylene terephthalate)

Dilute Solution Properties of Randomly Branched Poly(methyl methacrylate). II.

Abstract: Randomly branched polydisperse polymers prepared by copolymerization of methyl methacrylate with ethylene dimethacrylate were fractionated by the fractional solution technique. Light scattering, viscosity, osmotic pressure, and sedimentation measurements were carried out on the fractionated samples. It was found that in the theta state the intrinsic viscosity of a branched molecule obeyed Zimm and Kilb’s g1/2-rule, but in a good solvent it showed some deviation if the sample had many branch points. It was also found that the sedimentation constant of a branched molecule agreed with the theoretical value derived by Kurata and Fukatsu if the sample had a narrow molecular weight distribution.

A Hole Theory of Polymer Liquids and Glasses. I. Partition Function and Equation of State for Polymer Liquids

Abstract: A Hole Theory of Polymer Liquids and Glasses I Partition Function and Equation of State for Polymer Liquids

cis -Vinyl-1:1 Polymer of Butadiene

Abstract: With the catalyst system, Co(acac)3–AlEt3–H2O, cis-1,4–1,2-equimolar binary polybutadiene was obtained. The gas-chromatographic analysis of the ozonolysis product of the polymers showed that the sequence distribution was of the random but not alternating type. The preference of microstructure in polymerization is discussed briefly under the consideration of monomer coordination on the catalyst complex and the stability of the growing chain-end.

The Effect of Counteranions in the Polymerization of Isobutyl Vinyl Ether Initiated by Triphenylmethyl Cation

Abstract: The cationic polymerization of isobutyl vinyl ether was carried out at −75°C by using triphenylmethyl salts (Ph3C+X−, X−=BF4−, AlCl4−, AlBr4−, SbCl6− and SnCl5−) as initiator. The polymer was shown to contain the triphenylmethyl group. The extent of chain transfer, determined from the content of the triphenylmethyl group, was 0–4.4 in all the systems studied. These values are much smaller than those reported with BF3OEt2. The steric structure of the polymer was inferred from the precipitation temperature of the polymer in methyl ethyl ketone, Tp, as suggested by Okamura et al. Tp decreased with increasing polarity of polymerization solvents. In less polar media, Tp decreased in the following orderSnCl5−>SbCl6−∼AlBr4−>AlCl4−>BF4−.The observed order of Tp agreed with that of anion sizes, except for SnCl5−. Thus it is suggested that the steric effect of the counteranion is an important factor in deciding the steric course of propagation for tight ion-pairs. These results were explained within the framework of the steric course of the cationic propagation which we had proposed previously.

Thermal Conductivity of Cross-linked Polymers. A Comparison between Measured and Calculated Thermal Conductivities

Abstract: The thermal conductivity of the following cross-linked polymers was studied: (1) polystyrene cross-linked with divinylbenzene, (2) poly(methyl methacrylate) cross-linked with triallylcyanurate, (3) irradiated high-pressure polyethylene, and (4) epoxy resin cured with aliphatic amine. The thermal conductivity was found to increase with an increasing degree of cross-linking. The results were compared with calculated values obtained previously on the basis of the theory. The temperature dependence of the thermal conductivity was also discussed using the derived theory.

Thermodynamic Studies on the Glass Transition and the Glassy State of Polymers. II. Enthalpies and Specific Heats of Polystyrene Glasses of Different Thermal Histories

Abstract: Thermodynamic Studies on the Glass Transition and the Glassy State of Polymers. II. Enthalpies and Specific Heats of Polystyrene Glasses of Different Thermal Histories

Stereospecific Polymerization of Methyl α-Phenylacrylate

Abstract: The polymerization of methyl α-phenylacrylate was carried out in toluene by n-BuLi at −78∼30°C. The yield of the polymer was highest at −45°C and then decreased with increasing the temperature. No polymer was obtained above 0°C. The polymer obtained at −78°C was rich in isotacticity. By increasing the polymerization temperature the fraction of isotactic triads decreased in association with the increases in the fracrions of heterotactic and syndiotactic triads. Above −45°C, the proportion, I:H:S of the polymer obtained was close to 1:2:1, suggesting the random stereoregulation in the propagating step. The random polymer was also obtained by n-BuLi in polar solvent such as THF at low temperature as well as by AIBN. The addition of a small amount of methanol to the polymerization system by n-BuLi in toluene increased the yield, isotacticity, and molecular weight of the polymer, and the maximum values were obtained at CH3OH/n-BuLi=0.83. The polymerization by (iso-Bu)2AlNPh2 in toluene at −78°C gave a syndiotactic polymer in low yield. The reactivity of methyl α-phenylacrylate in anionic polymerization is briefly discussed in comparison with those of some other methyl α-alkylacrylates.

Stereoregularities of Ring-containing Polymethacrylates Obtained by Radical Polymerization

Abstract: Phenyl, 2-naphthyl(2-Np-MA), 1-naphthyl(1-Np-MA), 9-fluorenyl, 5,6,7, 8-tetrahydro-1-naphthyl, cyclohexyl(CH-MA), cyclopentyl(CP-MA), and decahydro-2-naphthyl(D-MA) methacrylates were polymerized in bulk, benzene, and n-hexane by radical initiators. The polymers were converted into poly (methyl methacrylate)(PMMA) by hydrolysis followed by methylation. The tacticities of the polymers were studied by comparing the IR and NMR spectra of the derived PMMA’s. The polymers containing aromatic substituents were more isotactic than conventional PMMA, and especially poly(2-Np-MA) prepared in n-hexane and poly(1-Np-MA)’s were considerably isotactic. On the other hand, tacticities of poly(CH-MA)’s, poly(CP-MA)’s, and poly(D-MA)’s were nearly the same as those of conventional PMMA. These results suggest that aromatic rings of the methacrylates seem to promote the formation of isotactic sequence and this effect is enhanced with naphthyl groups, but the aliphatic rings have little effect on such stereoregulation.

The Effect of Counteranions on the Polymer Steric Structure in the Cationic Polymerization of α-Methylstyrene

Abstract: The cationic polymerization of α-methylstyrene was carried out at −78°C by using Lewis acids and triphenylmethyl salts as initiator. The polymerization with triphenylmethyl salts was much slower than that with Lewis acids. The triad tacticity data of the polymer determined by NMR spectroscopy fitted the theoretical curve of one parameter (Bovey’s σ value). The σ value, though almost independent of the initiator used in CH2Cl2–CH3CN (σ≅0.04), increased with decreasing polarity of polymerization solvents and varied moderately (0.07–0.34) with the initiator in nonpolar solvents. In the case of triphenylmethyl salt initiators, the order of counteranions with increasing σ value (SnCl5−≳SbCl6−>AlBr4−> AlCl4−>BF4−) was the same as that observed for the isotactic propagation of isobutyl vinyl ether. These results were interpreted within the framework of the cationic propagation scheme proposed by us earlier. The steric influence of counteranions was discussed, and the unusual effect of SnCl5− was considered in connection with its coordination state. The variation of the σ value with Lewis acids (SnCl4 excluded) was much smaller than that with triphenylmethyl salts.

Comparison between the Conformations of Short Broken Chains and Stiff Chains

Abstract: A comparison is made of the second and the fourth moments of the end-to-end distances of several broken chain models with those of continous stiff chains. A shift factor f is introduced in such a way that n=fLD, where n is the degree of polymerization in the broken chain, L is the contour length and L/D is the mean square end-to-end distance in the limit of the long stiff chain. A single f-value is found to yield a good coincidence of both the second and the fourth moments of the end-to-end distance of the broken chain with those of the stiff chain. Values of the shift factor f which make the best coincidence of the conformations of the broken chains and the stiff chain are 1.66 for the freely rotating chain, 10.49 for the polymethylene chain and 9.18 for the chain with independent hindrance-potentials of the polymethylene type.

Effect of 1,2-Glycol Structure and Stereoregularity of Poly(vinyl alcohol) on Poly(vinyl alcohol)–Iodine Reactions

Abstract: Effect of 1,2-Glycol Structure and Stereoregularity of Poly(vinyl alcohol) on Poly(vinyl alcohol)–Iodine Reactions

Copolymerization of Carbon Dioxide with Optically Active Propylene Oxide

Abstract: Alternate copolymerization of carbon dioxide with optically active propylene oxide using a diethylzinc–water system as catalyst was investigated. The hydrolysis of the copolymer, poly(propylene carbonate), followed by subsequent treatment with p-nitrobenzoyl chloride, transformed the epoxide unit of the copolymer into the form of propylene glycol bis-p-nitrobenzoate. The determination of the optical activity of this ester led to the conclusion that the ring opening of propylene oxide takes place predominantly at the methylene–Oxygen linkage in the copolymerization, which suggests the anionic nature of the reaction. The optical rotatory behavior of the copolymer is also described.