bluuebunny/crossref_metadata_2025 huggingface dataset:
Calorimetric study of mixtures of butyl methacrylate oligomers with methanol
Authors: Pouchlý J. , Máša Z. , Biroš J. , Živný A. , Trekoval J.
Published: April 2003

Heats of mixing of methanol with butyl isobutyrate and with oligomers of butyl methacrylate (monomer to tetramer) having a butoxyl group on one chain end have been measured. To discuss the effect of hydrogen bonding on the heat values, it is appropriate to correlate the heat per mole of binding sites with the binding site fraction. This dependence can be described by a single curve for all oligomers studied, in contrast to the results obtained in a previous paper for the same oligomers with chloroform. This fact suggests that the binding parameters for methanol are not influenced by the degree of polymerization.
Radical formation during tensile deformation of highly drawn crystalline poly[p‐(2‐hydroxyethoxy)benzoic acid] fibers
Authors: Nagamura Toshihiko , Fukitani Kazunori , Takayanagi Motowo
Published: April 2003

The micromechanism of tensile deformation of poly[p‐(2‐hydroxyethoxy)benzoic acid] fibers is discussed on the basis of a detailed esr study of radical formation. The concentration of primary phenoxy radicals, which were detected during deformation at room temperature as a direct indicator of main‐chain rupture, was determined by extrapolating the radical decay curves at various strains to zero time. The relation between the initial radical concentration and the strain is well expressed by the cumulative normal distribution curve. By use of this relation and a model of fiber structure, the distribution of the contour length of tie chains was determined. No radicals were detected during a second stretching cycle until the maximum strain in the first run was exceeded. The deformation model which includes alternating crystalline and amorphous regions connected by tie chains, a distribution of contour lengths of tie chains, and a phase transformation of molecular chains in the crystalline region accounted fairly well for the observed stress–strain behavior of monofilaments in first and second stretching cycles. The comparison between the observed and the calculated radical concentration suggests that statistical factors and other deformation mechanisms have to be taken into account.
Excluded volume study of a sulfonate‐containing polyelectrolyte in salt solutions
Authors: Tan J. S. , Gasper S. P.
Published: April 2003

Chain characteristics of a linear sulfonate‐containing homopolymer, sodium poly(3‐methacryloyloxypropane‐1‐sulfonate), in aqueous salt solutions (ionic strength, Cs = 0.01N to 5N NaCl) have been investigated by light scattering and intrinsic viscosity. The molecular weight (M̄w)–viscosity relation can be well described by the Mark–Houwink and the Stockmayer–Fixman equations. The coil is highly expanded even in the most concentrated NaCl solution (6N), and no 1:1 electrolyte was found to precipitate this polymer.

A linear relation was observed between the viscosity expansion factor, α3η, and (M̄w/Cs)1/2. Examination of the data in terms of theories for excluded volume and hydrodynamic interaction suggests that the coil experiences dominant hydrodynamic interaction, corresponding to a nondraining coil, and the second virial coefficient and coil expansion at high Cs can be correlated by the Flory–Krigbaum–Orofino equation. Results for this polymer are compared with those for other polyelectrolytes, and are discussed in terms of chain structure, flexibility, and hydrophobicity.
Mechanisms of frequency shifting in the infrared spectrum of stressed polymer
Authors: Wool Richard P.
Published: April 2003

In the vibrational spectrum of a polymer obtained under tensile stress loading conditions, several modes of molecular deformation can lead to different mechanisms of frequency shifting and asymmetric band deformation. Theoretically and experimentally it has been observed that quasielastic deformations (reduction of force constants due to bond weakening under stress), pure elastic bond stretching and angle bending, conformational variations, and several types of chain defects can cause linear shifts in frequency and infrared band distortion. A detailed study of the deformation spectra of isotactic polypropylene and polyphenyl‐p‐sulfide indicated that quasielastic and elastic mechanisms are the major contributors to frequency shifting, principally affecting stretching and bending vibrational modes. Conformational mechanisms can affect torsional modes whereas the defect mechanism, when present, can cause random distortion of an infrared band. The latter mechanism is difficult to quantize. The extent to which each mechanism contributes to the total spectral deformation can be a function of morphology, macroscopic loading conditions, thermal and strain histories.
Deformation and microstructure of extended‐chain polydiacetylene crystals
Authors: Baughman R. H. , Gleiter H. , Sendfeld N.
Published: April 2003

The mechanical properties (Young's modulus, ultimate tensile strength, deformation processes) of extended‐chain polydiacetylene crystals are investigated. The properties observed are similar to those of metal and ceramic whiskers. The elastic modulus is strain‐dependent and the ultimate tensile strength increases with decreasing crystal size. The maximum tensile strength observed was 1700 Nmm−2. The ultimate tensile strength seems to be controlled by the presence of a small number of defects near the surface at which fracture nucleates. Irreversible deformation of the crystals was observed to occur by crack propagation normal and parallel to the direction of the macromolecules. The observed mechanical behavior corresponds to exceptionally high per‐chain properties. The per‐chain modulus obtained for these crystals is nearly as high as that of diamond. A chain‐aligned polyethylene fiber with the same per‐chain mechanical properties would have an ultimate strength as high as 0.9 × 104 Nmm−2.
Ion clustering studies in poly(butadiene–styrene–4‐vinylpyridine) crosslinked by iron (III) chloride. Differential enthalpic analysis and electron microscopy
Authors: Pineri M. , Meyer C. , Bourret A.
Published: April 2003

A terpolymer of butadiene–styrene–vinylpyridine has been crosslinked by addition of iron chloride. Differential enthalpic analysis gives evidence of a two‐phase system. Electron microscope studies at 0.1 and 1 MeV show the existence of precipitates. The majority of these ironrich aggregates have diameters less than 100 Å. Their form is polyhedral but very nearly spherical. No crystallinity has been detected inside the clusters. Thus the existence of strong interactions as in crystals of FeCl3 hydrates is excluded.
Pressure dependence of dielectric properties of chlorinated polyethylene vulcanizate. III. β relaxation
Authors: Naoki Motosuke , Nose Takuhei
Published: April 2003

The effects of temperature and pressure on the shift factor and the dielectric increment of the β relaxation process were measured for vulcanized chlorinated polyethylene. The isobaric and isochoric activation enthalpies, H*P and H*V, the activation volume V*, the pressure dependence of the glass–glass transition temperature, Tgβ/dP, and the apparent extinction temperature T0β were obtained. The pressure dependences of both V* and the dielectric increment would reach very small values near the liquid–glass transition temperature Tg, and the β process seems to be affected by the transition near Tg. The value of H*v/H*p for the β process is larger than that for the α process, and it is suggested that the molecular motions pertaining to the β process are more strongly restricted than those pertaining to the α process. The ratio T0β/T0, where T0 is the characteristic temperature in the Vogel–Fulcher–Tammann–Hesse equation for the α process, follows the empirical relation of Matsuoka and Ishida, Tgβ/Tg ∼0.75. The value of dTgβ/dP estimated from Tg and T0β/T0 is consistent with the experimental value.
Threshold fracture energies for elastomers
Authors: Ahagon A. , Gent A. N.
Published: April 2003

Fracture energies have been measured for two types of polybutadiene elastomer, crosslinked to various extents and torn under various conditions. Threshold values, ranging from 40 to 80 jm−2, were observed for samples torn at extremely low rates of tearing, at high temperatures, and in the swollen state. These values were found to be independent of temperature and rate of tearing, and also of the degree of swelling and the nature of the swelling liquid, provided a correction is made for the reduced areal concentration of molecular chains. They decreased somewhat with increased crosslinking, in good agreement with theoretical predictions of Lake and Thomas.6 The results for the two elastomers were substantially the same.

These observations are strikingly different from those made at normal temperatures and rates of tearing, when large differences in fracture energy were observed between the elastomers, and between samples crosslinked to different extents, due to energy losses from nonequilibrium deformation processes in addition to the energy required for fracture.
Crystallization during polymerization of poly‐p‐xylylene. III. Crystal structure and molecular orientation as a function of temperature
Authors: Iwamoto Reikichi , Bopp Richard C. , Wunderlich Bernhard
Published: April 2003

Polymerization of p‐xylylene was carried out from the gas phase with monomer produced by the pyrolysis of [2,2]‐p‐cyclophane. The crystalline form and preferred orientation of as‐polymerized polymer deposited at various temperatures (−196 to 80°C) were investigated by x‐ray diffraction methods. The melting behavior and other thermal transitions were studied by DSC. At 80°C the polymer film deposit is a mixture of the α and β forms, while between 60 and 0°C the deposit is of the α form. At lower temperature the polymer deposit is mainly of the β form, which shows diffuse reflections. At liquid nitrogen temperature it is of the β form with sharp reflections, contaminated with a small amount of oligomer. It was also found that at low temperatures, fibrillar crystals grow from the substrate in a direction 45° against the gas flow, and at even lower temperature, well‐oriented filmlike crystals grow perpendicular to the substrate surface.
Nucleation and growth of new crystals within polyethylene films during surface‐controlled recrystallization
Authors: Petermann J. , Gleiter H.
Published: April 2003

Observations by transmission electron microscopy suggest that surface‐controlled recrystallization of polyethylene occurs by the solid state nucleation and growth of new crystals with (110) or (110) planes parallel to the free surface. The nucleation site of these crystals is the free surface. The growth process involves the migration of [002] tilt boundaries suggesting that these boundaries have high mobilities. The migration process may occur by the lateral rearrangement of the macromolecules in the [002] tilt boundary.
The orientation of amorphous chains in spherulites
Authors: Petraccone V. , Sanchez I. C. , Stein R. S.
Published: April 2003

A theory for amorphous orientation in spherulitic polymers is presented based upon a consideration of conformational changes in the chains, loops, and cilia located between crystalline lamellae within a spherulite which is assumed to undergo an affine deformation. Chain statistics are worked out on the basis of (a) an analytical method involving random walks on a cubic lattice between barriers following a technique proposed by DiMarzio and Rubin and (b) a Monte Carlo computer simulation on a tetrahedral lattice. The latter method is considered more appropriate in view of the chain constraints such that lattice geometry becomes important. Values of the amorphous orientation are calculated as a function of the degree of crystallinity, initial lamellar separation, mole fraction of bonds in amorphous chains of each type, and chain lengths of each type of amorphous chain. It is found that tie chains are the principal contributor to amorphous orientation and the amount increases with increasing fraction and decreasing length of these. Results are compared with measurements of amorphous orientation by the birefringence x‐ray and the infrared dichroism technique. It is concluded that the tie chains must be initially quite highly elongated and that the assumed affineness of spherulite deformation is not closely obeyed.
Morphology of ultradrawn polyethylene strands. II. Nitric acid etching and melting behavior
Authors: Weeks Norman E. , Porter Roger S.
Published: April 2003

A transparent, ultraoriented, high‐density polyethylene morphology has been produced by solid‐state (ultradraw) extrusion in a capillary rheometer. From the perspective of modulus and nitric acid etching behavior, the uniquely high draw ratios (<325) experienced by the polyethylene during extrusion result in a morphology with a high level of chain extension. The effect of nitric acid etching on strand thermal behavior has been determined by DSC. The observed melting points of unetched strands were sensitive to the thermal contact between sample and sample pan. Under conditions ensuring improved contact, strand superheating is reduced to one‐third of previously reported values. The negligible shrinkage evidenced by these strands up to 130° is consistent with the presence of a thermally stable component such as extended chain crystals or crystallized tie chains. The single, high‐melting peak is gradually replaced by a nonsuperheating, lower melting peak during the initial stages of acid etch. The resultant peak melting temperature is consistent with the value predicted for the peak crystal thickness of the etched polymer. No evidence is found for a higher melting peak attributable to the extended chain crystalline component. A highly constrained morphology produced by the large tie chain content is believed responsible for strand melting behavior. The melting point of the extended chain crystalline component is reduced by defects and a large ratio of lateral to basal surface area.
Computer simulation of brownian motion of a polyelectrolyte molecule (charged bead‐spring model)
Authors: Fujimori Susumu , Nakajima Haruhiko , Wada Yasaku , Doi Masao
Published: April 2003

A Langevin equation of motion for a charged bead‐spring statistical chain is written in difference form and the relaxation and equilibrium behavior of the chain is studied by computer simulation. Results are presented for the behavior of end‐to‐end length h, principal axes of the polymer ellipsoid L1, L2, L3, and chain contour length c in terms of their averages, root mean square values, root mean square fluctuations, orientations, and relaxation strengths and times. The simulation was made with various sets of parameters, bead number N, charge on the bead q, and radius of ion atmosphere around the bead k−1. It is found that 〈h2〉1/2 and 〈L12〉1/2 increase more strongly with increasing q and decreasing κ than 〈L22〉1/2, 〈L32〉1/2, and 〈c12〉1/2, indicating that the chain is expanded in three dimensions and at the same time is extended along the end‐to‐end direction. The relaxation time τrot of rotation of the end‐to‐end vector, which is proportional to N2 at q = 0, increases with increasing q and tends to be proportional to N3 for an extended chain, while the relaxation time τconf of the magnitude of h is almost independent of q and is always proportional to N2. It is concluded that the extended chain possesses a well‐defined end‐to‐end axis and the chain rotates as a whole with a relaxation time τrot which is much longer than τconf. The complex viscosity of the chain is calculated from the Fourier transform of the time–correlation function of momentum flux and is found to have a frequency spectrum similar to that observed for aqueous solutions of poly(acrylic acid). The dominant mode appearing in the low‐frequency range is evidenced to arise from the rotation of the extended chain.
The crystal structure of poly(tetramethylene terephthalate)
Authors: Mencik Z.
Published: April 2003

The unit cell of poly(tetramethylene terephthalate) is triclinic with parameters a = 5.96 Å, b = 4.83 Å, c (fiber axis) = 11.62 Å, α = 115.2. β = 99.9, and γ = 111.3°; space group P1, calculated crystalline density 1.41 g/cc. The plane of the benzene ring is found to be inclined by about 15° from the fiber axis, contributing to a shortening of the fiber period as compared to the period expected on the basis of analogy with other members of the terephthalate ester series. The remaining shortening of the fiber period occurs in the O°CH2°CH2segment of the chain. No abnormally short distances among neighboring chain atoms were observed. A typical texture pattern was found in specimens of this polymer that were cold rolled and subsequently annealed. In this texture the c axis of the unit cell is highly oriented in the rolling direction; the a and b axes of the unit cell are oriented preferentially so that the terephthalate residue lies as close as possible to the plane of rolling.
Random‐coil dimensions of poly(methylphenylsiloxane) and their dependence on stereochemical structure
Authors: Mark J. E. , Ko J. H.
Published: April 2003

Rotational isomeric state theory was used to study the unperturbed dimensions 〈r2〉0 of poly(methylphenylsiloxane) (PMPS) chains [Si(CH3)(C6H5)O]x as a function of their stereochemical structure. The required conformational energies were obtained from semi‐empirical, interatomic potential energy functions and from known results on poly(dimethylsiloxane). PMPS chains were found to differ from monosubstituted and disubstituted vinyl chains primarily in the larger distance of separation between groups in conformations giving rise to “pentanetype interactions.” In PMPS, the relatively large distance of separation, 3.8 Å, makes such in teractions attractive, particularly in the case of two phenyl groups; in contrast, such interactions are strongly repulsive at the ∼2.5 Å separation characterizing vinyl chains. According to the calculated results, PMPS chains are very different from vinyl chains in that increase in isotacticity should cause a significant decrease in 〈r2〉0 and increase in d ln 〈r2〉0/dT. Comparison of theory with experimental results in the literature suggests that PMPS polymers which have been studied in this regard must have been significantly syndiotactic in stereochemical structure.
Dynamic mechanical properties of poly(2‐hydroxyethyl methacrylate) hydrogels
Authors: Nakamura Kunio , Nakagawa Tsurutaro
Published: April 2003

Homogeneous and heterogeneous poly(2‐hydroxyethyl methacrylate) hydrogels were prepared by copolymerization of 2‐hydroxyethyl methacrylate and small amounts of ethylene glycol dimethacrylate in the presence of water; concentrations of water (V1) in the polymerization mixture and the volume fractions of water (v1) of the gels swollen to equilibrium were 40, 50, 60, 70% by volume, and 0.475, 0.541, 0.669, 0.778, respectively. From the homogeneous (clear) hydrogel (V1 = 40%) preparation, four hydrogels were prepared with v1 = 0.434, 0.418, 0.378, 0.326. Tensile dynamic moduli were measured in the frequency range from 0.006 to 0.6 cps and the temperature range from 0 to 40°C. In these cases, the influence of swelling on the shape of the relaxation spectra and on the monomeric unit friction coefficient was studied. The dependence of the friction coefficient on water concentration was interpreted in terms of free volume. In the heterogeneous (opaque) gel preparations (V1 = 50, 60, 70%), the effect of the aqueous phase in the system on the mechanical behavior was described by a modification of the blending law of Ninomiya. For the systems with V1 = 60% and 70% the shapes of the storage and loss moduli in the main transition region and the friction coefficient were similar to those of the homogeneous gel with V1 = 40%, except for the decrease in absolute value of the storage moduli. For the system with V1 = 50% the shape of the relaxation spectrum changes appreciably and the wedge distribution does not hold.
Studies of the amorphous region of polymers. II. Relationship between change of structure and glass‐transition temperature in polycarbonate
Authors: Ito Eiko , Hatakeyama Tatsuko
Published: April 2003

A study of the effect of drawing on the glass transition temperature Tg of amorphous polycarbonate was carried out. The Tg attains a maximum at a draw ratio in the range from 1.6 to 2.0. The relationship between the change of structure and Tg is discussed in terms of the configurational entropy and the rate of molecular motion in local mode relaxation. The variation of Tg with drawing may be explained by using the iso‐entropy theory. The frequency of the maximum in the dielectric loss fmax and the dielectric relaxation strength Δε of the β mechanism changed with drawing in the same way as that of Tg. Based on the parallel behavior in these results, it is reasonable to consider that the β process of local mode relaxation of polyesters such as PC and PET reflects the structure of the glassy state.
The dynamic mechanical behavior of ultra‐high modulus linear polyethylenes
Authors: Smith J. B. , Davies G. R. , Capaccio G. , Ward I. M.
Published: April 2003

The dynamic mechanical properties of a number of ultra‐highly drawn polyethylenes have been studied over a wide range of temperature. It is shown that the materials possess low temperature Young's moduli as high as 1.6 Mbar, a figure which approaches the theoretical and experimental values for the c‐axis crystalline modulus of this polymer.

The α and γ relaxation processes are still clearly discernible even at highest drawn ratios (ca. 35) and a quantitative analysis of the results, using structural data obtained from broad line nuclear magnetic resonance (NMR) measurements, suggests that the data are consistent with a modified series model.
Dielectric relaxations in polymers with pendent phenyl or pyridine groups at temperatures from 4°K to 80°K
Authors: Shimizu Kazuharu , Yano Okimichi , Wada Yasaku
Published: April 2003

Isochronal measurements of dielectric loss are made for polystyrene (PS), poly(4‐vinyl pyridine) (P4VP), poly(2‐vinyl pyridine) (P2VP), poly(L‐phenylalanine) (PLPA), and poly(γ‐benzyl‐L‐glutamate) (PBLG) at temperatures ranging from 4°K to 80°K and at frequencies from 10 Hz to 100 kHz. PS, P4VP, and PLPA show loss peaks around 50°K (10 kHz) while P2VP exhibits a loss peak around 20°K (10 kHz). PBLG has no detectable peak in this temperature range. The 50°K and 20°K peaks are ascribed to wagging and rotation, respectively, of phenyl or pyridine groups between two energy minima. The barrier height and energy difference between the minima evaluated from the experimental data are reasonably explained by assuming that the double minima are caused by interaction between a pair of phenyl or pyridine groups, each belonging to adjacent chains which pack irregularly.
Heterogeneous nucleation of crystallization of high polymers from the melt. I. Substrate‐induced morphologies
Authors: Chatterjee A. M. , Price F. P. , Newman S.
Published: April 2003

Melt crystallization of isotactic polypropylene (iPP), poly(ethylene oxide), poly(butene‐1), and polycaprolactone in contact with various substrates (mostly polymeric) has been studied by hot stage polarizing microscopy. Nucleating abilities of surfaces have been characterized qualitatively by examining the substrate‐induced morphologies of the crystallizing polymer. These morphologies have been classified into three groups, depending on whether the substrate is very active (transcrystallinity), moderately active, or inactive as a nucleating agent. The morphologies observed are temperature‐dependent, changing from transcrystalline to spherulitic upon increase of the crystallization temperature. At intermediate temperatures, mixed surface morphologies (transcrystalline plus spherulitic) are observed.

The concentration of titanium and aluminum catalytic residues in isotactic polystyrene (iPS) samples can be reduced by two methods, i.e., (a) fractionating the polymer and (b) chelating Ti and Al with acetylacetone. The high nucleating ability of iPS samples in the crystallization of iPP has been shown to be due to the polymer (iPS) itself, and not to Ti and Al residues. Apart from iPS, other polymers (low energy surfaces) have also been found to induce transcrystallinity.

From a survey of 43 substrate‐crystallizing polymer pairs, conclusions have been drawn which are relevant to the following potential factors in heterogeneous nucleation processes: (a) chemical structure, (b) crystallographic unit cell type, (c) lattice parameters, (d) crystallinity of substrate, and (e) surface energy of substrate.
Quasielastic scattering by dilute polymer solutions
Authors: Akcasu Z. , Gurol H.
Published: April 2003

The scattering law S(k,w) for dilute polymer solutions is obtained from Kirkwood's diffusion equation via the projection operator technique. The width Ω(k) of S(k,w) is obtained for all k without replacing the Oseen tensor by its average (as is done in the Rouse–Zimm model) using the “spring‐bead” model ignoring memory effects. For small (ka\documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt N $ \end{document} ≪ 1) and large (ka ≫ 1) values of k we find Ω = 0.195 k2/β α η0 \documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt N $ \end{document} and Ω = k2/βξ, respectively, indicating that the width is governed mainly by the viscosity η0 for small k values and by the friction coefficient ξ for large k values. For intermediate k values which are of importance in neutron scattering we find that in the Rouse limit Ω = k4a2/12βξ. When the hydrodynamic effects are included, Ω(k) becomes 0.055 k3/βη0. Using the Rouse–Zimm model, it is seen that the effect of pre‐averaging the Oseen tensor is to underestimate the half‐width Ω(k). The implications of the theoretical predictions for scattering experiments are discussed.
Gelation‐crystallization in isotactic polystyrene solutions and its implications to crystal morphology, to the origin and structure of gels, and to the chemical homogeneity of polyolefins
Authors: Girolamo M. , Keller A. , Miyasaka K. , Overbergh N.
Published: April 2003

As part of a wider study on the crystallization of isotactic polystyrene solutions it was observed that at sufficient concentrations (> 3–5%) gelation sets in below a certain (very high) supercooling in competition with the usual single crystal formation which in itself produces turbid suspensions. It was established that gelation is a form of crystallization (mode A) which must be of fringed micellar type to provide the connectedness as opposed to the chain folded lamellae (mode B) which gives rise to discrete particles. The gel crystals (A) display sharp melt endotherms and produce distinct x‐ray diffraction patterns both of which, however, differ decisively from those provided by crystals B, a distinction which can be preserved even after removal of the solvent. The melting points of A are significantly lower than those of B and the x‐ray diffraction patterns of A are incompatible with the recognized structure of polystyrene (31 helix) possessed by B; they point to a broadly planar zig‐zag arrangement of the chain. This strongly suggests that we have blocks of chemically distinct sequences which could be syndiotactic or head‐to‐head tail‐to‐tail (presently with substantial support for the latter) which is responsible for the gel forming crystallization. However, so far the C13 nuclear magnetic resonance (NMR) results do not provide the evidence for these distinct species but explanations for our observations on any other basis seem to lead to unsuperable difficulties from other points of view. Consequently, the paper is left open ended with the possibilities discussed. Amongst these the existence of a very few but long, chemically distinct sequences seems most attractive. The wider implications of the facts as they stand for crystal morphology (fringed micelles versus lamellae), for the origin and structure of gels in general, for the crystallization of block copolymers and for issues relating to chemical homogeneity (tacticity, head‐to‐head tail‐to‐tail) are discussed and preliminary effects are quoted which indicate that these issues may also be relevant to the usual atactic polymers.
Mechanical loss processes in polysaccharides
Authors: Bradley S. A. , Carr S. H.
Published: April 2003

Dynamic mechanical properties of cellophane, amylose, and dextran have been obtained over the temperature range 100–520°K and frequency range 10−2 to 10+2 Hz on specimens containing various amounts of water. Four mechanical transitions have been characterized. At about 180°K, there is a γ transition that has been assigned to rotation of methylol groups; no comparable transition was found to exist in dextran. At about 240°K, there is a β transition that has been assigned to rotation of methylol–water complexes, but the β transition in dextran appears to be due to some other kind of motion. In cellophane at about 450°K there is an α2 transition which appears to have contributions from motion of chain segments in disordered regions. The α1 transition for cellophane occurs at temperatures too high to measure and may be due to segmental motions in chains within crystalline regions. Dextran and amylose were found to have at these same temperatures α loss processes that probably correspond to glass–rubber transitions in amorphous material. The changes in these mechanical loss mechanisms due to moisture uptake suggest that sorbed water associates with glucose repeat units in ways ranging from those which stiffen molecular structure to those which allow greater freedom for other types of motion to occur.
Solution behavior of styrene–ethylene oxide block copolymers
Authors: Nakamura Kanehiro , Endo Ryuichi , Takeda Masatami
Published: April 2003

Hydrophobic–hydrophilic water‐soluble block copolymers were prepared by “living” anionic polymerization. They consist of a polystyrene block and a polyethylene oxide block. From data on solution viscosity and high‐resolution NMR in water, the molecular dimensions of the two‐blocks copolymers are found similar to that of polyethylene glycols of the same molecular weight in the same solvent. These block copolymers exhibit microphase separation.
Ion binding in sulfonate‐containing polyelectrolytes
Authors: Tan J. S. , Marcus P. R.
Published: April 2003

Emf measurements have been used to study the activity and the extent of sodium ion binding to several polyelectrolytes, poly(styrenesulfonate) (PSS), poly(2‐acrylamido‐2‐methylpropanesulfonate) (PAMS), poly(3‐methacryloyloxypropane‐1‐sulfonate) (PMOS), and copoly[(N‐t‐butylacrylamide)‐(2‐acrylamido‐2‐methylpropanesulfonate)] (NB–AMS) (mole ratio 3.8:1). The activity coefficient of sodium ion in Na‐PAMS and Na‐PMOS without added salt is found to be in the range from 0.1 to 0.3 and is insensitive to changes in polymer concentration. However, it increases with increasing concentration of the added salt.

The extent of sodium ion binding at a given sodium ion concentration, as estimated from the activity data for some sodium and tetrabutylammonium (TBA) salts, decreases in the order Na‐PAMS ≈︁ Na‐PMOS > TBA–PAMS > TBA–(NB–AMS). This indicates that a significant portion of the binding is attributed to the binding of TBA+ ions. Also compared are the results of ion binding in Na‐PAMS and Na‐PSS as a function of ionic strength. At low ionic strength (<1.0M), the order of binding strength is Na‐PAMS > Na‐PSS, while the order is reversed at high ionic strength (>1.0M). This finding is in good agreement with data obtained by dilatometry and viscometry.
Structural studies of single spherulites and partially spherulitic films of poly(methyl‐D‐glutamate)
Authors: Wilkes Garth L. , Mohadger Youseph , Holaday William
Published: April 2003

Isolated spherulites of poly(methyl D‐glutamate) (PMDG) were nucleated in bromoform. The morphology of these spherulites was investigated by SEM and photographic small‐angle light scattering (SALS). From the SALS patterns, the development and growth of the spherulites could be noted. Films of PMDG cast from bromoform solution were found to be partially spherulitic. The mechanical properties of these films, prepared by different procedures, were compared with the general behavior of PMDG films cast from chloroform, the latter of which does not contain spherulitic texture.
The mechanical properties and structure of poly(m‐methylene terephthalate) fibers
Authors: Ward I. M. , Wilding M. A. , Brody H.
Published: April 2003

A study has been carried out of the differences in mechanical properties of oriented fibers of poly(ethylene terephthalate) (2GT), poly(trimethylene terephthalate) (3GT), and poly(tetramethylene terephthalate) (4GT). The properties studied include the tensile stress–strain behavior, the recovery from strain, shrinkage at 100°C and the glass‐transition temperatures. The stress–strain curves of the three materials differ markedly. 2GT shows a monotonic increase in stress with increasing strain up to failure, which occurs at ∼20% strain, and the oriented fibers possess a comparatively high initial modulus. 3GT shows a much lower initial modulus and there is an inflection in the stress–strain curve at about 5% strain. The stress–strain curve of 4GT shows a number of distinct features. Although the initial modulus of 4GT is similar to that of 3GT, the stress–strain curve shows a pronounced plateau in the region between 4% and 12% strain. At higher strains the stresses rise rapidly before failure. These features of the stress–strain curves in the three polymers can be related to previous studies where the x‐ray diffraction spectrum and the Raman spectrum have been examined for fibers under stress. The ranking of both the recovery and shrinkage behavior of these materials is in the order 3GT > 4GT > 2GT. These results can also be understood in terms of the results of the previous structural studies, and it is concluded that the molecular conformations in both the crystalline and noncrystalline regions play a key role in determining the mechanical behavior.
Investigation of poly(trans‐1,4‐butadiene) crystals using the spin‐probe method
Authors: Nagamura T. , Woodward A. E.
Published: April 2003

The spin‐probe technique has been employed to study the nature of the surface regions of poly(trans‐1,4‐butadiene) crystals grown from dilute heptane and toluene solutions. The narrowing of the ESR spectrum of the nitroxide radical probe added to the PTBD crystals and the activation energy for the rotational motion of the probes were found to very with the crystallization solvent and annealing temperature; in every case heptane‐grown crystals showed a higher line narrowing temperature and activation energy than toluene grown crystals. Annealing at 80°C raised the narrowing temperature and the activation energy for crystal preparations from both solvents used, but annealing at high temperatures, near to but below the melting point, lowered both parameters again. These results support earlier assertions, based on infrared spectra, surface epoxidation, differential scanning calorimetry, broad‐line nuclear magnetic resonance, and dynamic mechanical results concerning the nature and location of the amorphous regions in PTBD crystals.
Effect of concentration of the crosslinking agent and diluent during polymerization on the viscoelastic spectra of poly(2‐hydroxyethyl methacrylate) networks
Authors: Ilavský M. , Hasa J. , Vojta V. , Janáček J.
Published: April 2003

The effect of concentration of the crosslinking agent (ethylene dimethacrylate) and diluent (water) during the crosslinking copolymerization on the shape and position of retardation spectra in the dry state has been investigated for poly(2‐hydroxyethyl methacrylate) networks. With increasing water content during network formation, the maxima of the retardation spectra, Lm, increase and the position of the spectra is shifted toward shorter retardation times, τ. The results are in quantitative agreement with the modified Rouse–Mooney (R–M) molecular theory and suggest the influence of deformation due to the diluent during network formation on the viscoelastic behavior. With increasing content of the crosslinking agent, the retardation spectra are shifted toward longer times. At a constant reference temperature T0 = 115°C the retardation time, τm, at the maxima of the spectra increases with increasing content of effective chains in the network, νe. However, after a correction for the effect of the monomeric frictional coefficient, ξ, τm/ξ decreases with increasing ve at a rate which agrees quantitatively with the R–M theory. The slope of the retardation spectra in the main transition region and the value of their maxima decrease with increasing ve; a comparison of these dependences with theory leads to the most probable distribution of submolecules in the chains. The contribution of long retardation times to the equilibrium compliance, Je, of the systems under investigation was estimated; it was shown that the application of the Thirion–Chasset extrapolation method for the determination of Je of loose networks requires a certain type of dependence of the retardation or relaxation spectra on τ.
High‐pressure phases in polymers. IV. Skeletal growth in cis‐polyisoprene
Authors: Edwards B. C. , Phillips P. J.
Published: April 2003

The crystallization of cis‐polyisoprene even at moderately elevated pressures results in the formation of a single‐crystal species which develops through skeletal growth. The nature of these crystals, which are produced at relatively low supercooling, is described. They occur concurrently with spherulites but exhibit a much higher growth rate. In common with single crystals grown from solution the size and shape of the species is a function of the supercooling.
On the structure of glassy polymers. III. Small‐angle x‐ray scattering from amorphous polyethylene terephthalate
Authors: Renninger A. L. , Uhlmann D. R.
Published: April 2003

The small‐angle x‐ray scattering (SAXS) from glassy polyethylene terephthalate has been measured using a Bonse–Hart system. The data cover the angular range (2θ) between 20 sec and 2 deg. After correcting for absorption, background, and beam divergence, the data have been placed on an absolute basis by comparison with the scattering from a standard silica suspension. The corrected absolute intensity decreases strongly with increasing angle over the range between 20 sec and 15 min, decreases more gradually in the range between 15 min and 45 min, and reaches a nearly constant asymptotic value over the range between 45 min and 2 deg. The magnitude of the scattering in the constant range, about 0.4 (electrons)2 Å−3, is very close to the value predicted by the thermodynamic fluctuation theory for fluids applied at the glass‐transition temperature [0.34 (electrons)2 Å−3]. The increase in intensity at angles smaller than about 45 min cannot be described by structures on the scale and volume fraction of the nodules reported in amorphous PET (50–100 Å), but can be well represented by small concentrations of heterogeneities, ranging in size from 100 to 2000 Angstroms, superimposed on the thermal density fluctuations frozen‐in at the glass transition. The bulk structure of this material seems well described as a random amorphous solid, containing simple thermal fluctuations and a small concentration (<1 vol‐%) of heterogeneities covering a range of sizes. The heterogeneities in the small end of the range may well be crystallites which formed on cooling.
Thermal shrinkage of oriented semicrystalline poly(ethylene terephthalate)
Authors: Bhatt G. M. , Bell J. P.
Published: April 2003

The shrinkage of commercial oriented poly(ethylene terephthalate) filaments was studied within the framework of the kinetic theory of rubberlike elasticity. Previous workers had found that the shrinkage and optical behavior of amorphous polymers could be satisfactorily explained in terms of this theory. Such an analysis is now applied to semicrystalline samples of moderate and high draw ratios (from 2× to 6×).

It was found in this work that the thermal shrinkage force behavior as well as the optical anisotropy as a function of stretch can be explained in terms of the theory of rubberlike elasticity, if the following reasonable assumption is made: the average number of statistical segments per network chain in the noncrosslinked sample increases as a function of the draw ratio. A possible mechanism for such behavior is the relaxation of some of the chain entaglements due to the strain imposed externally on the fiber.
Morphology and modulus–temperature behavior of semicrystalline poly(ethylene terephthalate) (PET)
Authors: Groeninckx G. , Berghmans H. , Smets G.
Published: April 2003

The influence of the thermal history on the morphology and mechanical behavior of PET was studied. The degree of crystallinity (density measurements) and the morphological structure (electron microscopy and small‐angle x‐ray diffraction) depend on the crystallization temperature. The viscoelastic parameters obtained from the modulus–temperature curves are mainly determined by the morphology of the samples. The glass‐transition temperature, Ti, is a function of the crystallinity and the crystallization temperature. It is maximum for a crystallinity between 0.34 and 0.39 for a sample crystallized isothermally between 120 and 150°C. This dependence on crystallization conditions is ascribed to the conformation of the amorphous chain segments between the crystalline lamellae as well as the concentration and the molecular weight of the polymer material rejected during isothermal crystallization. Both factors are supposed to be temperature‐dependent.

The value of the rubbery modulus is a function of both the volume concentration of the crystalline lamellae and the structure of the interlamellar amorphous regions (chain folds, tie molecules, chain ends, and segregated low molecular weight material). Annealing above the crystallization temperature of isothermally crystallized samples has a marked influence on their morphology and mechanical behavior. The morphological structure and the viscoelastic properties of annealed PET samples are completely different from those obtained with samples isothermally crystallized at the same temperature.
Morphological mechanics of springy polymers
Authors: Wool Richard P.
Published: April 2003

The mechanics of “springy” or “hard elastic” row‐crystallized polymers were investigated. It was found that their unique tensile and physical properties could be explained by adhesive fracture mechanics and simple beam deflection. The deformed lamellae had an apparent negligible modulus of flexural rigidity. An adhesive failure model was designed which duplicated all the tensile characteristics of springy polymers, including constant lateral contraction, critical stress, peel stress, rehealing, energetic elasticity, and cyclic strain behavior. The ideal relative density change as a function of strain was found to be the same for all springy polymers. Dynamic infrared analysis showed that the molecular orientation decreased during the deformation of springy polypropylene films. The latter is due to the deflection of lamellae. Rehealing was accompanied by a time‐dependent reversal of orientation. The enthalpic elasticity is derived from the strain energy of the lamellar network.
Light scattering by helical fiber structures: Experimental models
Authors: Visconti S. , Hien N. V. , Borch J. , Marchessault R. H.
Published: April 2003

Samples of two helically wound monofilaments were used as experimental models to check the theoretical expression for light scattering from helixes. A method of estimating the pitch and tilt of the helixes was outlined and the results were compared with measurements from microscopy. The agreement was satisfactory. Layer line streaking and splitting was observed and explained in terms of irregularity of the helical parameters. Samples of several helically wound monofilaments were also prepared and their scattering patterns were compared with those from native and regenerated cellulosic fibers.
Acoustic emission of a crazing polymer
Authors: Grabec I. , Peterlin A.
Published: April 2003

The acoustic emission from a crazing polyvinyltoluene in a tensile and bending experiment is described. Acoustic emission appears as a series of bursts which most likely correspond to the initiation and growth of crazes. The emission intensity is characterised by acoustic activity (pulse rate) measured by the ring‐down technique. The average activity increases with strain. During repeated loading the acoustic activity shows a measurable intensity and significant rise only beyond the maximum strain of the former runs. This is equivalent to Kaiser's effect in metals. Acoustic emission during the creep experiment occurs in three characteristic periods. They are characterized as the relaxation, fatigue, and breakdown periods. Visual observations indicate that the relaxation period corresponds to the initiation, and the fatigue period to the growth of crazes. In the breakdown period a macroscopic crack develops and the sample fails.
Effect of partially immobilizing sorption on permeability and the diffusion time lag
Authors: Paul D. R. , Koros W. J.
Published: April 2003

The gas permeability and diffusion time lag may exhibit varying degrees of pressure dependence for glassy polymers. The sorption isotherm appears to consist of contributions from both Langmuir and Henry's law terms in such systems. This “dual sorption” theory advanced in the literature pictures gas held by the Langmuir mode as being completely immobilized. In the present paper, this model is extended to accommodate different degrees of partial immobilization of gas sorbed by this mode using two different formulations. One uses a transport expression based on concentration gradients while the other is based on chemical potential gradients. The predictions are that: (1) total immobilization results in a constant permeability with a time lag which strongly decreases with pressure; (2) no immobilization results in a constant time lag with a permeability which decreases strongly with pressure; and (3) incomplete immobilization results in both the permeability and time lag decreasing with pressure but neither as strongly as in the other limiting cases. The differences which may arise by the two formulations of the model are discussed.
The mechanical behavior of poly(methyl methacrylate) under pressure
Authors: Matsushige K. , Radcliffe S. V. , Baer E.
Published: April 2003

Tensile deformation of poly(methyl methacrylate) carried out under hydrostatic pressures up to 4 kbar has shown that the pressure‐transmitting fluid (silicone oil) strongly affects the mechanical properties of this polymer. Unsealed specimens fractured in a brittle manner at almost the same strain of 5% in the whole pressure range examined, while specimens sealed with Teflon tape and rubber showed a brittle to ductile transition at only 0.25 kbar. At this pressure, the craze initiation and shear band initiation stresses were found to become equal. The pressure dependence of the shear band initiation stress could be expressed well with a “nonlinear” pressure‐dependent von Mises criterion and the onset of the shear banding was proved to relate to the enthalpy energy density stored in the specimen. The combination of the nonlinear pressure‐dependent von Mises criterion and the enthaply energy density concept enabled us to predict the pressure dependence of Young's modulus.
Brillouin scattering from amorphous bisphenol‐A polycarbonate
Authors: Patterson G. D.
Published: April 2003

Brillouin scattering has been studied from amorphous bisphenol‐A polycarbonate in the temperature interval 60–240°C. Both longitudinal and transverse Brillouin peaks are observed over the entire range. The behavior of both types of Brillouin splittings, Δωl and Δωt, in the region of the glass–rubber relaxation is typical of an amorphous polymer. Equilibrium values of Δωl and Δωt were obtained 20°C below the glass‐transition temperature Tg determined at cooling rates of 20°C/hr. Comparison of the present results with previous ultrasonic data reveals a considerable dispersion in the longitudinal phonon velocity below Tg. The origin of the large transverse Brillouin intensities is related to the structure of polycarbonate.