bluuebunny/crossref_metadata_2025 huggingface dataset:
Lactone polymers. VIII. Dynamic mechanical properties of ϵ‐caprolactone and γ‐(tert‐butyl)‐ϵ‐caprolactone copolymers
Authors: Seefried C. G. , Koleske J. V. , Critchfield F. E.
Published: April 2003

The temperature dependencies of dynamic mechanical properties have been determined with a torsional pendulum for copolymers of ϵ‐caprolactone and γ‐(tert‐butyl)‐ϵ‐caprolactone over the entire composition range. Copolymers containing at least 25 mol % (33 wt %) of γ‐(tert‐butyl)‐ϵ‐caprolactone units are amorphous in nature. The experimentally obtained glass transition temperatures of the copolymers and poly(γ‐(tert‐butyl)‐ϵ‐caprolactone) were used to calculate the glass transition temperature of amorphous of poly(ϵ‐caprolactone) according to the Fox relation. This value of −70°C is in excellent agreement with values obtained from similar calculations based on compatible blends of poly(ϵ‐caprolactone) with other homopolymers.
The nature and origin of structural defects in polymeric sulfur nitride
Authors: Baughman R. H. , Chance R. R.
Published: April 2003

Defect structures in (SN)x crystals obtained by solid‐state polymerization are so numerous and varied that they are likely to conceal inherent property aspects of the defect‐free polymer. In addition to frequent macroscopic twinning, three different kinds of defect sites are observed. These sites are related to the disruption of molecular orientational order about the chain axis direction and the sequencing of chain types in the periodic phase. The origin of these defects is explained by the nonuniqueness of solid‐state polymerization and recrystallization processes, which transform the initial dimer phase to the final polymer phase. The orientational relationship between the dimer and polymer phase is predicted from the observed twinning mode and the structural relationship between these phases. The change from dimer phase (at zero and at intermediate conversions involving solid solution formation) to polymer phase can be described by a shear transformation on the (001) dimer plane. This observation suggests an analogy with known martensitic reactions and a method for improving the perfection of (SN)x.
The hydrodynamic properties of the cellodextrin alditols
Authors: Tostevin James E. , Swenson Harold A.
Published: April 2003

Diffusion coefficients of cellodextrin alditols from DP 1 to 5 in 0.32 molar NaOH are found to be 22% less than in water. Slightly lower diffusion rates and higher friction coefficients and Einstein–Stokes hydrodynamic radii are also reported for the alditols as compared to cellodextrins in water. Considered as ellipsoids based on diffusion rates, the length‐to‐width ratio for the alditols, only slightly greater than for the cellodextrins in water, increase by about 100% in alkali. A similar increase in axial ratio is shown for cellodextrins in the highly alkaline solvent cadoxene as for the alditols in alkali. It is suggested that creation of the large frictional envelope occurs in alkali prior to complexing with the common cellulose solvents in which complexing with copper, cadmium, and iron in divalent from are involved. The possible nature of the enlarged frictional domain is discussed.
Surface energies of chain molecules from homogeneous nucleation
Authors: Calvert P. D.
Published: April 2003

A model for the interpretation of homogeneous nucleation data for chain molecules is presented. The two surface energies σs and σe are related to interchain and intrachain bonding. Surface energies calculated from experimental data on n‐alkanes from octane to dotriacontane and polyethylene agree with estimated values. The results are discussed in relation to surface energies measured from spherulite growth rates in polymers but these values are not known with sufficient reliability to provide a good basis for comparison.
Mechanical relaxations in some ionene polymers. I. Effect of Ion concentration
Authors: Tsutsui Tetsuo , Tanaka Ryuichi , Tanaka Takehide
Published: April 2003

Dynamic mechanical properties of m,n‐ionenes, the structure of which are shown in Figure 1, were examined by torsional braid analysis. Three relaxations designated as α,β and γ were found. The α relaxation, ascribed to the primary relaxation due to an amorphous phase, was observed at 70–130°C, the temperature increasing with an increase of the ion concentration along the polymer chains. The β relaxation at around 0°C was related to the ionic portions of the polymers. The γ relaxation at around–120°C was a so‐called local mode relaxation. The γ relaxation peak was split into two peaks in the very slowly cooled 12,10‐ionene sample and the formation of an inhomogeneous structure in the amorphous phase is proposed.
Dielectric relaxations in a series of vinyl aromatic polymers: Poly(2‐vinyl‐N‐ethylcarbazole), poly(3‐vinyl‐N‐ethylcarbazole), poly(2‐vinylanthracene), and poly(α‐methyl‐2‐vinylanthracene)
Authors: Pochan J. M. , Hinman D. F.
Published: April 2003

Two dielectric relaxations have been studied on poly(2‐vinyl‐N‐ethylcarbazole) (P2VK) and poly(3‐vinyl‐N‐ethylcarbazole)(P3VK), poly(2‐vinylanthracene) (P2VA) and poly(α‐methyl‐2‐vinylanthracene) (PMe2VA). The relaxations in P2VK and P3VK occur in the temperature regions 220°C and −150°C. Evidence for a third relaxation in both polymers at ca. 120°C has been found; and, for this reason, the relaxations studied (220°C and −150°C) are labeled α and β, respectively, and have been attributed toTgand carbazole rotational libration about the bond connecting the carbazole moiety to the polymer backbone. Additionally β (ca. 20°C) and γ(ca. −150°C) relaxations in P2VA and MeP2VA have been observed and assigned, respectively, to wagging motion and rotational libration of the pendant anthracene moiety.
Dynamics of macromolecular chains. V. Interpretation of the dielectric relaxation data
Authors: Gény F. , Monnerie L.
Published: April 2003

The autocorrelation function of orientations, derived for the model of conformational jumps in a chain described in a tetrahedral lattice, has been tentatively applied to dielectric relaxation data. The complex dielectric relaxation of polymers can be interpreted by the aid of only two relaxation processes. In the case of poly(p‐chlorostyrene) in solution, the characteristic times that we have calculated agree favorably with the fluorescence‐depolarization results. The model has been shown to be consistent with the empirical decay function exp[− (t/τ)β] proposed by Williams.
The study of domain structure in polyurethanes by nuclear magnetic resonance
Authors: Assink R. A.
Published: April 2003

Polyurethanes are block copolymers composed of hard and soft segments which often undergo microphase separation with the resultant formation of hard and soft domains. The nuclear‐magnetic‐free induction decay of such systems is shown to consist of a fast Gaussian component corresponding to glassy domains and a slow exponential component corresponding to rubbery domains. Thus, by being sensitive to the microscopic mobility of a material, nuclear magnetic resonance (NMR) has the potential to determine when a polyurethane has separated into domains and the relative amounts of material in each domain. After annealing the free‐induction decay of a linear polyurethane showed a distribution of relaxation times indicating that mixing of the domains had taken place and a continuum of compositions exist in the material. The free‐induction decay of a cross‐linked polyurethane was unaffected by annealing, confirming the results of an earlier study.
On‐line viscometry combined with gel permeation chromatography. I. Instrumental calibration and testing with linear polymers
Authors: Park Won S. , Graessley William W.
Published: April 2003

Gel permeation chromatography (GPC) was combined with flow time measurements on the eluent to provide both the distribution of hydrodynamic volumes and the distribution of intrinsic viscosities in linear polymers. Standard polystyrene samples were used to establish a universal hydrodynamic volume calibration as well as the zone spreading and viscometer transfer line tailing parameters. Viscometry data are particularly helpful in establishing the zone spreading parameters and the calibration curve at very high molecular weights. The results were applied to measurements on samples of linear polybutadiene and polyvinyl acetate. Agreement between values of Mw from GPC with those obtained by light scattering confirmed the universal calibration principle.
Inhomogeneous polymer solutions: Theory of the interfacial free energy and the composition profile near the consolute point
Authors: Vrij A. , Roebersen G. J.
Published: April 2003

The Flory–Huggins formulation of the combinatorial entropy, supplemented with residual free energy, is applied locally to obtain the interfacial free energy and the concentration profile of polymer in the interface between two demixed polymer solution phases. Two choices were investigated for the residual free energy: a “regular solution” formulation and an empirical formulation of Koningsveld for polystyrene in cyclohexane. Asymptotic, analytical solutions of the equations near the critical solution point and solutions obtained by numerical calculations are given as a function of temperature for several molecular weights. At temperatures farther below the critical temperature the equations have no solutions. The reason for this is not entirely clear. The local formulation of the free energy used here is an improved version of a previous one, which gave wrong results for asymmetric systems (polymer in a low molecular weight solvent). This newer version is consistent with our theory of critical opalescence and gives a relation between the interface “thickness” and the correlation range of the concentration fluctuations. The calculated correlation ranges were in good accord with those found experimentally by Debye, Chu, and Woerman. That the newer version of our equations for an interface gives no acceptable solutions at lower temperatures could be caused by a “collapse” of a diffuse to a sharp interface as suggested by Nose.
Studies of the polymerization of diallyl compounds. XXV. Gel point in the polymerization of diallyl esters of aromatic dicarboxylic acids
Authors: Matsumoto Akira , Yokoyama Shigeyuki , Khono Tetsuro , Oiwa Masayoshi
Published: April 2003

Studies on gelation in the radical polymerization of diallyl dicarboxylates have been conducted by Simpson,9,11 Gordon,10 and Oiwa.13 However, the results obtained have not always been consistent and are still far from full elucidations. In this paper, the gel point in the polymerization of diallyl aromatic dicarboxylates, including diallyl phthalate (DAP), diallyl isophthalate (DAI), and diallyl terephthalate (DAT) is experimentally reexamined in detail and discussed according to Gordon's theory; the discrepancy between actual and theoretical gel point conversion was quite large and was enhanced in the order DAT > DAI > DAP. Moreover, from detailed inquiry into the primary chain length of the prepolymer it is suggested that the intramolecular chain transfer reaction plays an important role in the polymerization of diallyl ester accompanying the intramolecular cyclization reaction. The polydispersity coefficient (Pw,0/Pn,0) of the initial prepolymer of DAP is also estimated to be 2.0 from the extrapolation of Pw/Pn to zero conversion.
Phase‐separation phenomena in solutions of poly(2,6‐dimethyl‐1,4 phenylene oxide). II. Differential scanning calorimetry of solutions in toluene
Authors: Koenhen D. M. , Smolders C. A.
Published: April 2003

The phase‐separation phenomena observed in solutions of poly(2,6 dimethyl‐1,4 phenylene oxide) in toluene have been investigated by differential scanning calorimetry. These measurements supplement the experimental evidence in favor of the concept that the phase transitions observed are crystallization and melting phenomena. The experiments suggest that two kinds of crystals can develop and that a seeded crystallization is possible.
Four‐center photopolymerization in the crystalline state. VIII. X‐ray crystallographic study of the polymerization of some diolefinic compounds
Authors: Nakanishi Hachiro , Hasegawa Masaki , Sasada Yoshio
Published: April 2003

The four‐center photopolymerization of five diolefinic compounds has been investigated by x‐ray crystal analysis. A common packing feature is found for the photopolymerizable crystals and all polymers are three‐dimensionally oriented. Topotaxies observed are classified according to the coincidence of space group and the three crystal axes, between monomer and polymer. The polymerization mechanism is discussed on the basis of the topotaxies and it is concluded that the polymerization is lattice controlled over the whole reaction process.
Thermally stimulated discharge current studies on the effect of thermal treatment on the strength of polycarbonate
Authors: Aoki Y. , Brittain J. O.
Published: April 2003

It is well known that polycarbonate annealed at 80–130°C undergoes gradual changes in mechanical properties. Annealing below Tg (ca. 150°C) results in a decrease in impact resistance and an increase in strength. Polycarbonate has three single relaxation processes and some distributed relaxation processes in the temperature range between 100 and 250°K (the β transition region). The effect of thermal pretreatment on the relaxation has been investigated by the thermally stimulated discharge current technique. Partial heating, peak cleaning, and theoretical fitting have also been performed and the activation parameters associated with the relaxation processes have also been calculated to assist in the analysis of the relationship between effects of annealing and structural motions in polycarbonate.
Analysis of anomalous X‐ray diffraction effects of isotactic polystyrene gels and its implications for chain conformation and isomeric homogeneity
Authors: Atkins E. D. T. , Isaac D. H. , Keller A. , Miyasaka K.
Published: April 2003

Oriented gels, obtained by high supercoolings of isotactic polystyrene solutions, exhibit unexpected “fiber‐type” x‐ray diffraction patterns. In particular a pronounced meridional reflection at a spacing of 0.51 nm, together with its successive orders, requires an extended, or nearly extended, chain conformation which appears irreconcilable with the stereochemistry of isotactic polystyrene. Furthermore, the value of 0.51 nm correlates directly with the axial projected repeat expected for two styrene monomer units. Two possible stereosequences merit atention: syndiotactic and syncephalic (head‐to‐head, tail‐to‐tail). In addition to the 0.51 nm meridional reflection, layer lines are observed with spacing 3.06 nm (6 × 0.51) which equate with 24 carbon–carbon bonds in the backbone. Cylindrically averaged Fourier transform calculations for the various models are compared with the observed x‐ray results and the best fit is obtained for a 24/11 helix of isolactic polystyrene with the syncephalic stereosequence. This conclusion, however, clashes with the 13CNMR evidence which indicates that the polymer is essentially isotactic. The implications of these novel results in relation to gel crystallization are discussed.
Acoustic absorption and dynamic compressibility studies of dilute and concentrated solutions of polystyrene in toluene and cyclohexane
Authors: Dunbar Janice I. , North Alastair M. , Pethrick Richard A. , Steinhauer Daniel B.
Published: April 2003

Acoustic absorption and adiabatic compressibility measurements are reported on solutions of polystyrene (Mn = 89,000) in toluene and cyclohexane. The data in toluene cover a temperature range from 293 to 343°K and a concentration range of 10–400 Kg m−3 (1–40 wt%). The dependence of acoustic absorption on concentration was found to be linear up to 100 kg m−3, which corresponds to the concentration at which polymer–polymer interactions cause significant changes in the specific viscosity‐concentration relationship. Up to 200 kg m−3 the data could be fitted to computations based on an artificial separation of the dispersion into contributions from viscoelastic and segmental processes, using parameters obtained from a study of narrow molecular weight distribution samples at 25 kg m−3. However, neither approach was capable of describing dispersions in the 300, 400 kg m−3 solutions. The modification of the relaxation spectrum observed at the highest concentrations is ascribed to volume and entropy changes associated with alterations of the local environment around a segment of the polymer chain. These changes have their origin in interchain penetration and polymer–polymer contacts, and indicate that ‘entanglement’ is primarily entropic in effect.

The adiabatic compressibility exhibited similar deviations from a simple concentration dependence, and allowed estimation of an incompressible volume increment associated with polymer–polymer interactions in the high‐concentration entangled matrix. However, the adiabatic compressibilities of solutions of polystyrene, 10–15 kg m−3, in cyclohexane showed no deviations from simple behavior in the region of the theta temperature. Measurements of the adiabatic compressibility of polystyrene in mixtures of cyclohexane‐toluene have been used to obtain the relative magnitude of solvent and polymer contributions to the excess compressibility.
Automated light‐scattering apparatus for studying polymer films
Authors: Chu W. H. , Horne D. E.
Published: April 2003

The design and operation of an automated light‐scattering apparatus for studying structures in polymer films are described. The apparatus has angular resolution of 0.02 and 1.0° in radial and azimuthal angles, respectively. The radial scan can be made over the range of 0.5 (or less) to 90° and the azimuthal scan covers 180°. Time resolution is in the order of milliseconds. The operation, data collection, and reduction are fully automatic. Illustrative data on the crystallization of a low density polyethylene are described.
Photoelectret state in poly(vinylcarbazole)
Authors: Pillai P. K. C. , Agarwal S. K. , Nair P. K.
Published: April 2003

The photoelectret charge in the aluminum–poly(vinylcarbazole) (PVK) conducting‐glass (NESA), sandwich cell configuration has been observed to decrease with voltage above some critical voltage, depending on the intensity of illumination. This critical voltage corresponds to the value at which a time‐independent photocurrent is observed and also to the “knee‐point” voltage in the current voltage plot. The results are explained on the basis of field‐assisted detrapping setting in at high field.
Diffusion in polymer–solvent systems. III. Construction of Deborah number diagrams
Authors: Vrentas J. S. , Duda J. L.
Published: April 2003

A method is presented for anticipating condition under which anomalous diffusion effects can be expected for amorphous polymer–solvent systems. The diffusion process is characterized by a dimensionless group called the diffusion Deborah number, and a method for calculating this dimensionless number is presented. Deborah number diagrams are constructed for the unsteady diffusion of ethylbenzene and polystyrene in thin films, and observed diffusion phenomena are discussed on the basis of these diagrams.
Properties of cellulose acetate in solution. II. Light scattering and elasticity measurements on gels in benzyl alcohol
Authors: Goebel K. D. , Berry G. C.
Published: April 2003

Kinetic studies are reported for the light scattering and elasticity of thermally reversible gels of cellulose acetate in benzyl alcohol over a range of temperature and polymer concentration. The small‐angle light scattering data are found to be described by exponential correlation functions, and it is concluded that the scattering has its origin in the nonrandom character of the crosslinking in the gels studied. The elasticity is discussed in terms of the density of crosslinks in the gels. Thus, the kinetics studied by light scattering and elasticity measurements are independently related to temperature and polymer concentration.
Dielectric relaxations in linear aliphatic polyesters
Authors: Ito M. , Nakatani S. , Gokan A. , Tanaka K.
Published: April 2003

Molecular motions in a series of linear aliphatic polyesters [poly(ethylene adipate), poly(ethylene sebacate), poly(hexamethylene sebacate), and poly(decamethylene 1,16‐hexadecanedicarboxylate)] were studied by dielectric measurements. Two loss maxima were observed for each polymer in the temperature range from −196 to about 60°C and in the frequency range from 110 to 105 Hz. The loss maxima of these polyesters, lying between −17 and −38°C at 110 Hz (β‐relaxation), are due to the micro‐Brownian motions of amorphous main chains. It was found that these β‐relaxations are well described by the WLF equation. The loss maxima in the range from −88 to −109°C at 110 Hz (γ‐relaxation), are attributed both to local mode motions of main chains in the amorphous region and to motions of the polar groups involved at the chain ends. For the β‐relaxation, no simple relation between the methylene sequence length and the loss peak temperature was found. Furthermore, as the methylene sequence length decreased, the effective dipole moment of the polyesters increased gradually. These facts were explained in terms of interchain dipole attraction.
Aspects of plastic scintillators. II. Energy transfer studies in polymerizing media
Authors: Neilson R. D. M. , Soutar I. , Steedman W.
Published: April 2003

Changes in scintillation efficiency during formation of plastic scintillator compositions have been studied. The separate roles of energy transfer and solute fluorescence efficiencies in the determination of the observed luminescence output of the systems were elucidated. Bis‐1,4‐2‐(5‐phenyloxazolyl)benzene(POPOP); 1,1′,4,4′‐tetraphenylbutadiene(TPB), and 9‐methyl anthracene (MAN) were employed as scintillator solutes. The increased scintillation yield of polymerizing solutions of POPOP is primarily a consequence of increased energy transfer efficiency from solvent to solute. Solutions of TPB exhibit enormous increases in luminescence output upon formation of polymers. The major contributor to the overall effect is the great enhancement of the fluorescence efficiency of TPB which occurs when the microviscosity of the medium is increased. MAN solutions exhibit a decreasing luminescence yield upon polymerization despite increasing energy transfer efficiency. Structural rearrangements of the fluor, consequent upon involvement in the polymerization kinetic chain, are responsible for the decreased scintillation efficiency.
Internal viscosity in the dynamics of polymer molecules. II. A new model for the Lamb–Matheson–Philippoff increment
Authors: Macinnes D. A.
Published: April 2003

We propose a new model for the Lamb–Matheson–Philippoff (LMP) increment in the dynamical viscosity of polystyrene solutions. The crucial difference between the new model and the currently accepted models is that our model predicts that at least a large part of the LMP increment relaxes at a particular frequency, whereas the conventional models predict a nonrelaxing increment. In order to derive our model, we reformulate the internal viscosity (IV) concept, for a fluid undergoing shear, in such a way that the shear filed appears explicitly in the IV resistance. Since the derivation of this IV model is nonrigorous and produces a result which may be surprising, we rederive the dynamical viscosity using a correlation function technique, into which the flow field does not enter explicitly. We show that our model predicts the principal experimental results on the LMP increment as well as the conventional models do, but that our model gives a result which is more in line with current thinking (i.e., that the increment might be expected to undergo relaxation). We also show that our model accurately predicts an “anomalous” result obtained recently on the viscoelastic absorption spectrum of poly(propylene glycol) melts, the description of which is quite outside the scope of the Rouse–Zimm model or the currently accepted IV model.
Effects of diluent on molecular motion and glass transitions in polymers. III. The system poly(vinyl acetate)–toluene
Authors: Adachi Keiichiro , Hattori Mitsuhiro , Ishida Yoichi
Published: April 2003

Dielectric measurements, differential thermal analyses (DTA), and broad‐line proton magnetic resonance (NMR) measurements are reported on the system poly(vinyl acetate)–toluene. Four dielectric relaxations were observed between 80 and 400°K. From proton NMR measurements on solutions in toluene and in deuterated toluene, the relaxation processes can be assigned, respectively, to segmental motion of poly(vinyl acetate), α; motion of side group, β′ rotation of toluene, β; local motions of poly(vinyl acetate) and toluene, γ, in order of appearance with decreasing temperature. Two stepwise changes in DTA traces have been observed and can be assigned as glass transition points TgI and TgII. Comparison of these glass transition points with temperatures at which dielectric relaxation times for the α and β processes are 100 sec, indicate that segmental motion of poly(vinyl acetate) and rotation of toluene are frozen‐in at TgI and TgII, respectively. Activation plots for the α process conform to the Vogel–Tamman equation. In terms of the parameters A, B, and T0 of the equation, TgI can be represented by an expression of the form TgI ≈ T0 + B/(A + 3). In the range of concentration above 50% by weight, A and B are almost independent of concentration but T0 varies strongly. The nature of the secondary dispersions is also discussed.
A new method for the study of molecular motion in polymeric solids: Thermally stimulated creep
Authors: Monpagens J. C. , Chatain D. G. , Lacabanne C. , Gautier P. G.
Published: April 2003

We propose a new method for the investigation of molecular motion in polymeric solids. In a mechanical step‐function experiment, we thermally stimulate the response to a constant stress. The high resolving power of this technique permits detailed study of the complex retardation modes observed in polymers. As an example, we consider the thermally stimulated creep of low density polyethylene. The experimental resolution of the thermally stimulated creep spectra shows the existence of elementary processes well fitted by the assumption of single retardation times.
Structural changes on hot‐rolling of polyethylene. I. Crystallite orientation and lamellar deformation
Authors: Yoda Osamu , Kuriyama Isamu
Published: April 2003

The crystallite orientation and lamellar deformation produced by hot‐rolling in polyethylene have been investigated. In the lightly rolled stage, the [110]* axis of polyethylene crystals orientates in the plane perpendicular to the rolling direction and the c axis becomes aligned with the rolling direction. In the heavily rolled stage the a, b, and c axes coincide with the macroscopic directions in the sample. These orientational changes are interpreted in terms of a slip mechanism. Small‐angle x‐ray scattering (SAXS) investigations of hot‐rolled polyethylene show the following. (1) There are two kinds of lamellar structures; one in which inclined lamellae give a four‐point diagram in the SAXS photograph and another in which lamellar normals are oriented around the rolling direction even at the lightly rolled stage. The latter structure is attributed to the mechanism of unfolding and recrystallization. (2) The chain‐fold length in the original structure remains unchanged in the lamellae up to a roll ratio of four although the apparent long period decreases. This is explained by inclination of polymer chains in the lamellae. Further rolling aligns the polymer chains with the rolling direction and the fold length decreases.
Effect of drawing on the melting point and heat of fusion of polyethylene
Authors: Sumita Masao , Miyasaka Keizo , Ishikawa Kinzo
Published: April 2003

The melting point and the heat of fusion were measured by differential scanning calorimetry (DSC) as a function of draw ratio for linear polyethylene. Both the melting point and the heat of fusion increased with an increase in draw ratio. The plot of the heat of fusion against the melting point was approximately linear. The linear relation is explained theoretically using the assumption that the increases in the melting point and the heat of fusion are due to the orientation of the amorphous phase caused by drawing. The excess free energy of the amorphous phase derived from the orientation increases the melting point, and the amorphous phase absorbs heat for its randomization at the melting point. Hence for drawn samples having an oriented amorphous phase not only the crystal phase but also the amorphous phase contribute to the heat of fusion.
General properties of secondary relaxations in polymers as determined by the thermally stimulated current method
Authors: Vanderschueren J.
Published: April 2003

The method of thermally stimulated current (TSC) has been used to study the low‐temperature dielectric β relaxations of several polymers including especially poly(vinyl chloride), poly(vinyl acetate), polyamide 6, 6,6,poly(t‐butyl acrylate), poly(methyl methacrylate), poly(ethyl methacrylate), poly(phenyl methacrylate), and poly(t‐butyl methacrylate). The distribution characteristics of the relaxation processes have been determined from the corresponding TSC peaks by a fractional polarization technique which consists of applying the electric field in several discrete steps during a slow cooling. Several common features have been found in all the polymers investigated: the β peaks are characterized by a distribution of relaxation times resulting from a distribution in activation energy and this distribution is quasisymmetrical and continuous. These facts are in agreement with the hypothesis of a relaxation involving local motions of small polar groups undergoing various interactions with the environment. Some discrepancy remains, however, between our calculated values of the mean activation energy and those obtained from the dielectric loss.
Dielectric study on copolymers in dilute solution. Relaxation behavior of methyl methacrylate–styrene and methyl methacrylate–α‐methylstyrene copolymers
Authors: Iwasa Yasuo , Chiba Akio
Published: April 2003

Dielectric measurements were made on some methyl methacrylate (MMA)‐related polymers in dilute solution, in the frequency range of 1–150 MHz. Effects of the solvent viscosity upon the relaxation behavior were carefully examined. The dielectric relaxation of MMA–styrene copolymers with a high content of MMA units as well as that of the MMA–α‐methylstyrene copolymer was little affected by the solvent viscosity. With the aid of Kramers'rate constant for small friction, it was found that their dipolar relaxation is very similar to that caused by the internal rotation of a flexible side‐chain. On the other hand, MMA–styrene copolymer with a low content of MMA units showed a diffusion‐controlled relaxation process, which can be interpreted in terms of Kramers' theory for large friction. In the latter case, the dipolar relaxation appears to reflect a molecular motion such as sweeping out solvent molecules. These results indicate that it is not the dipole itself but its environment, or rather the local molecular structure containing dipoles, that principally controls the relaxation process. On this basis, we propose a criterion, for quantitatively distinguishing the two relaxation mechanisms from each other.
Hydrogen catalysis of alkyl radical decay in single crystalline polyethylene
Authors: Patel V. M. , Dole Malcolm
Published: April 2003

Although hydrogen gas is about tenfold more soluble in hot‐filtered mats of polyethylene (PE) single crystals (SC) than in bulk linear PE, we found that no hydrogen solubility at all could be measured in freeze‐dried SC. Despite this, hydrogen gas still exerts a catalytic effect on alkyl radical decay on both the fast and slow first‐order decay reactions in the freeze‐dried samples. Above 40°C the first‐order decay constants of the slowly decaying component decrease with increasing fold period.
Study of the viscoelastic behavior of uncrosslinked (gum) rubbers in moderately large deformations
Authors: Chang W. V. , Bloch R. , Tschoegl N. W.
Published: April 2003

Two models, one for materials possessing a well‐defined reference state (solid‐like behavior, model S), the other for materials lacking such reference (liquid‐like behavior, model L) were tested with the aid of experimental data obtained in various strain histories in simple tension on an uncrosslinked styrene–butadiene rubber (SBR) gum rubber over the temperature range from −20 to 23°C.

The models resulted from the introduction of the nonlinear n‐measure of strain into the Boltzmann superposition integral. Both gave excellent predictions of the response of the SBR to step and to ramp functions of strain. Published data on the response of polyisobutylene to an exponential stretch ratio excitation were in similarly good agreement with both models. Sensitive tests in which small deformations were superposed on a finite stretch allowed a distinction to be made in favor of model S.

In uncrosslinked materials the strain parameter n was found to be small (typically about 0.5) and sensibly independent of temperature in the range investigated. By contrast, in crosslinked rubbers, n is typically between 1 and 2 at room temperature and generally decreases with temperature. The dependence of n on the nature of the material, crosslink density, temperature, and crosslinking conditions was examined.
Plastic fracture
Authors: Cornes P. L. , Smith K. , Haward R. N.
Published: April 2003

It has been previously shown that when rigid poly(vinyl chloride) is extended by fully necking the test‐piece, subsequent fracture takes place by a novel mechanism. Surface crazes grow into “diamond” ‐shaped cavities which slowly expand while retaining their shape. We have now found that this new mechanism is of general applicability to a wide range of plastics which fracture after yielding. Examples are given from polycarbonate, poly(ether sulfone), and poly(methyl methacrylate) broken at elevated temperatures. The form of the diamond cavity is determined by the continuation of plastic deformation in the whole test‐piece while the diamond grows bigger. After fracture a characteristic cavity is left behind on the fracture surface which demarcates the zone of slow growth. At a given point, which is generally easily observable on the fracture surface, the crack speeds up. This change is believed to correspond to a situation where enough elastic energy is available to propagate a crack. It is favored, not only by the increase in size of the diamond in the test‐piece but also by an increase in the average energy stored per unit volume of material.
Thermoluminescence of irradiated poly(methyl methacrylate)
Authors: Radhakrishna S. , Murthy M. Rama Krishna
Published: April 2003

Thermoluminescence of poly(methyl methacrylate) (PMMA) irradiated with x rays, has been studied in the temperature range 100 to 460°K. Two glow peaks with maxima at 136 and 368°K have been observed. These are analyzed by three methods and the results are compared. Both curves obey second order kinetics and correspond to activation energies of 0.17 and 0.88 eV, respectively. It is possible to identify the centers responsible for the two peaks by correlation with electron spin resonance and optical data obtained for the same samples irradiated under the same conditions. Spectral studies of the emission show that the low temperature peak has its maximum at 365 nm while the high temperature peak has its maximum at 480 nm.
The effect of molecular weight heterogeneity on the second virial coefficient of linear polymers in good solvents
Authors: Noda Ichiro , Kitano Toshiaki , Nagasawa Mitsuru
Published: April 2003

The effect of molecular weight heterogeneity on the second virial coefficient A2 in good solvents is studied for binary mixtures of monodisperse poly(α‐methylstyrenes). It is concluded that A2 for polymer mixtures passes through a maximum with variation of the mixing ration. From comparison with the data, it is concluded that no available theory quantitatively explains both the molecular weight dependence of A2 of monodisperse polymer and the variation of A2 of mixtures with the mixing ratio. The interpenetration function for two polymer coils with different molecular weights is discussed on the assumption that the thermodynamic interaction between two polymer coils in good solvents can be approximated by a hard‐sphere model.
A fourier transform infrared spectroscopic investigation of polyethylene single crystals. II. Fine structure of the CH2 rocking mode
Authors: Painter P. C. , Havens J. , Hart W. W. , Koenig J. L.
Published: April 2003

The application of the spectral subtraction routine to an analysis of the CH2 rocking mode of polyethylene single crystals is discussed. A difference band at 716 cm−1 characteristic of a local monoclinic arrangement of chains is detected. Oxidation of crystal mats by nitric acid indicates that these defect structures are located inside the crystal and are not associated with the fold surface.
Thermoluminescence of irradiated polystyrene
Authors: Radhakrishna S. , Murthy M. Rama Krishna
Published: April 2003

Thermoluminescence of irradiated polystyrene has been studied in the temperature range 100 to 440°K. Three glow peaks with maximum at 160, 221, and 378°K have been observed. These peaks are analyzed by different methods and the activation energies which were obtained are compared. The activation energies are found to be 0.22, 0.48, and 1.45 eV for the peaks with maxima at 160, 221, and 378°K, respectively. Second‐order kinetics is appropriate to all these cases. The glow peaks are attributed to the decay of the free radicals formed on irradiation and subsequent thermal stimulation. The peak with the maximum at 160°K is attributed to electron trapping by the carbonyl groups or peroxy radicals formed on irradiation. The curve with the peak at 221°K is attributed to the cyclohexadienyl radical, and the curve with the peak at 378°K is attributed to the chain radical CH2C (C6H5)CH2. The centers responsible for the observed thermoluminescence are identified by correlation with electron spin resonance (ESR) data obtained on the same samples.
Crystallization of bisphenol‐A polycarbonate. II. Melting behavior and equilibrium melting temperature of the plasticized polymer
Authors: Legras R. , Mercier J. P.
Published: April 2003

The melting behavior of bisphenol‐A polycarbonate samples plasticized by tritolyl phosphate (TTP), pentaerythritol tetranonanoate (PETN), and trimellitic acid–tridecyloctyl ester (TMDO) has been investigated and discussed on the basis of current theories. Using the Hoffman and Weeks approach modified for finite chain length, the variation of the equilibrium melting temperature has been determined as a function of the plasticizer concentration. Extrapolation of these data yields an equilibrium melting temperature of 317°C for the pure polycarbonate of infinite molecular weight. This figure greacly exceeds the value so far reported in previous publications. It is also shown that the compatibility of the plasticizer affects the melting temperature just as it controls the glass transition. The cryoscopic effect observed, however, is much more pronounced than anticipated on the basis of the Flory–Huggins theory.
Solid‐state relaxations in poly(ethylene oxide). I. Study using the differential scanning calorimetry method
Authors: Lang M. C. , Noël C. , Legrand A. P.
Published: April 2003

Differential scanning calorimetry (DSC) studies show that poly(ethylene oxide) (PEO) exhibits three transition regions below its melting point. The effects of annealing on the intensity and temperature of these transitions enable us to locate T < Tg (Tγ) Tg, and Tα at about 130–140. 190–240, and 263–313°K, respectively. Our results argue for a small transition Tg (L) at 190–200°K with a second Tg (U) above 233°K, the temperature of which increases on annealing. The shape of DSC derivative curves reveals that T < Tg and Tα are complex and suggests the possibility of two steps in these processes. In addition, a splitting of Tα is observed every time a multiple melting endotherm appears as a result of annealing. Up to three separate melting endotherms can be observed. One of them is related to the normal primary crystallization process. Its peak temperature increases linearly with the annealing temperature, yielding an extrapolated value for the equilibrium melting temperature T of 347°K as found before.
Fluorine magnetic relaxation in poly(p‐fluorostyrene) and poly(m‐fluorostyrene)
Authors: Matsuo Keizo , Kuhlmann K. F. , Yang H. W.‐H. , Gény F. , Stockmayer W. H. , Jones Alan Anthony
Published: April 2003

The spin‐lattice relaxation time and the nuclear Overhauser enhancement (NOE) of 19F nuclei in dilute solutions of poly(p‐fluorostyrene) and poly(m‐fluorostyrene) were measured as a function of molecular weight, concentration, temperature, solvent, and field strength. Models for local motion of the chain backbone based on independent internal rotations or on one‐dimensional defect diffusion failed to provide a quantitative description of both T1 and the NOE. A model based on three‐bond crankshaft motions and a cutoff of coupling along the backbone gives a consistent account of these results as well as 13C nuclear magnetic resonance (NMR) relaxation data on polystyrene from the literature. The model provides a finite set of exponential correlation times to describe local motion, the center of the distribution lying in the nanosecond region for dilute solutions of polystyrenes in normal solvents. The apparent activation energy for the backbone motion obtained from the temperature dependence of the average correlation time based on NMR data is about 20 kJ mole−1. The local correlation times based on NMR are appreciably shorter than those determined by dielectric relaxation. This discrepancy points to the existence of several different local motions which make different contributions depending upon the experimental technique employed.
Thermally induced conformational changes in poly(vinyl chloride)
Authors: Koenig J. L. , Antoon M. K.
Published: April 2003

Fourier transform infrared spectroscopy has been used for the detection of thermally induced conformational changes in atactic poly(vinyl chloride) (PVC). Difference spectra emphasize changes in the distribution of gauche defects in the chains as functions of temperature and annealing. Specific bands in the ν(CCl) and δ(CH2) regions varied with inverse temperature, allowing a calculation of the activation energies of the rotamer species. Conformational changes were also detected in quenched PVC films as a result of annealing below the glass transition temperature, Tg.
Monomer distributions and number‐average sequence lengths in hydrogenated butadiene–styrene copolymers from carbon‐13 nuclear magnetic resonance
Authors: Randall James C.
Published: April 2003

Monomer distributions and number‐average sequence lengths are determined from 13C nuclear magnetic resonance (NMR) data for 1,4‐ and 1,2‐butadiene additions and styrene additions in a series of four hydrogenated butadiene–styrene copolymers. The monomer distribution is expressed in terms of the six unique days from which it is possible to calculate the number‐average sequence length of each monomer type. Carbon‐13 NMR spectral assignments are given and the techniques for making the assignments are discussed. The method presented could, in principle, be applied to any copolymer or terpolymer. Limitations that are encountered in the analysis of hydrogenated butadiene–styrene copolymers high in 1,2 additions are discussed.
Solution grown isotactic polystyrene crystals. I. Degree and distribution of crystallinity; thermal stability
Authors: Overbergh N. , Girolamo M. , Keller A.
Published: April 2003

The subject of this paper is the degree of crystallinity and annealing behavior of solution grown single crystals of isotactic polystyrene (IPS) in relation to the fold length, an enquiry which acquires special significance in view of the fact that previously the fold length had been found to be identical over a wide range of crystallization temperatures (Tc). It was found that both crystallinity and thermal stability increase with Tc even over the range of constant fold length thus invalidating the usual assumption that the fold length and crystal properties are uniquely correlated. Further, the crystallinity figures as measured by conventional calorimetry are very low (<50% throughout) which by conventional ideas would require an unrealistically thick amorphous surface layer. However, the “linear crystallinity” (crystal core thickness as determined from x‐ray linewidths) is much larger, commensurate with crystallinities in single crystals from other materials. It is suggested that this is the more relevant figure for the subdivision of the lamellas into crystal core and surface layer. The additional amorphous content being otherwise accommodated. Further, this “linear crystallinity” is broadly unaffected by fold length changes induced by heat annealing. The thermal stability (including annealing ability) of the crystals differs markedly whether Tc is above or below ∼60°C, a Tc value which is in the range where the fold length is constant, but corresponds to a maximum in the crystallization rate. Possible connections between crystallization conditions and the stability of the resulting crystals (fold length considerations apart) are pointed out.
Melting of constrained drawn nylon 6 yarns
Authors: Todoki Minoru , Kawaguchi Tatsuro
Published: April 2003

A differential scanning calorimeter (DSC) was used to study the melting behavior of drawn nylon 6 yarns which were prevented from shrinking during heating. The DSC curves exhibit a single melting peak at a higher temperature instead of the double peaks which, as reported previously, were observed in the unconstrained state. The curve is explained quantitatively in terms of the perfecting of the original crystals followed by monotonic melting of these crystals during heating. The single peak results from the absence of the partial melting–recrystallization process which plays an important role in the appearance of double peaks. The temperature of the melting peak for the constrained sample increases linearly with draw ratio, and is unaffected by drawing temperature and by annealing at constant length after drawing. The elevation of the melting temperature is discussed on the basis of the entropy effects predicted theoretically by Zachmann. Thermal analysis of constrained samples has proved to be useful for detecting oriented crystals which coexist with unoriented ones.
Fourier‐transform infrared study of polyethylene single crystals in suspension
Authors: Painter P. C. , Runt J. , Coleman M. M. , Harrison I. R.
Published: April 2003

The infrared spectra of polyethylene single crystals suspended in liquid are reported and compared to dried mats of the same material. In order to observe the polyethylene bands, liquids with partial windows in complementary regions of the spectra were chosen. Any remaining bands of the suspending media were removed by substraction of the spectrum of the pure liquid. The crystalline bands of suspended polyethylene are much sharper than those of the dried material, indicating a decrease in lateral crystalline order upon drying. Drying also results in a change in the type and distribution of conformations associated with amorphous and fold structures, as determined by the observed frequencies of the methylene wagging mode.
Oriented crystallization of biphenyl in low‐density polyethylene with a single texture
Authors: Dosière M. , Point J. J.
Published: April 2003

Doubly oriented specimens with a single texture can be obtained by unidirectional rolling of a sheet of low‐density polyethylene. Swelling of the oriented samples with liquid biphenyl and in situ crystallization of the biphenyl give indirect information about the morphology of the polymer. In such samples, annealed a few degrees below the melting temperature, the orientation of the biphenyl crystals is a consequence of the interaction of the two crystalline lattices. The (001) biphenyl planes are parallel to the (h01) limiting planes of the lamellar polymer crystals. Theoretical considerations show that the epitaxial conditions are best fulfilled when the limiting planes of the lamellas are parallel to (201) planes. The experimental value of h is 3.