bluuebunny/crossref_metadata_2025 huggingface dataset:
Solid‐State 13C‐NMR detection of the isotropic carbonyl line shape in blends of poly(vinylphenol) with main‐chain polyesters
Authors: Belfiore Laurence A. , Qin Chuan , Ueda Eiji , Pires Alfredo T. N.
Published: April 2003

The solid‐state NMR isotropic line shape of the carbonyl 13C resonance is useful as a qualitative diagnostic probe of the polyester component′s morphology and molecular mobility in partially miscible blends with poly(vinylphenol), PVPh. The main‐chain polyesters chosen for investigation in this study are poly(ethylene succinate), poly(ethylene adipate), poly(butylene adipate), and poly(caprolactone). A crystalline phase exists for polyester‐rich mixtures in all cases. Verification of this claim is provided by DSC endothermic tran‐sitions that map out melting point depression in the temperature‐composition phase dia‐grams. The carbonyl 13C‐NMR signal in the crystalline domains exhibits a full width at half height of 1–2 ppm when the glass transition temperature of the blends is below the temperature of the NMR experiment. In all cases, a single concentration‐dependent glass‐transition temperature is measured by DSC, which increases monotonically from below ambient for polyester‐rich blends to well above ambient for blends that are rich in poly(vinylphenol). When the concentration of the amorphous proton donor PVPh is suf‐ficient to thwart crystallization of the polyester and increase the glass transition temperature of the blends above the temperature of the NMR experiment, the line width of the carbonyl resonance increases three‐ to fourfold to ca. 5–6 ppm. When the blends are completely amorphous and Tg is above ambient, the polyester carbonyl 13C line shape reveals at least two morphologically inequivalent microenvironments. A partially resolved carbonyl signal in rigid amorphous blends is (a) identified at higher chemical shift relative to the crystalline component, and (b) attributed to hydrogen bonding in the amorphous phase. This inter‐action‐sensitive hydrogen‐bonded carbonyl signal accounts for an increasing fraction of the overall NMR absorption envelope of the carbonyl carbon site when the polyester is saturated with PVPh. The main‐chain polyesters were chosen to probe the effect of chemical structure of the proton acceptor on the potential for hydrogen‐bond formation. Aliphatic CH2 spacers between the carbonyl groups dilute the concentration of interacting sites, and the dependence of the carbonyl 13C‐NMR line shape on blend concentration reveals unique spectroscopic behavior in each of the four blend systems investigated. © 1993 John Wiley & Sons, Inc.
A qualitative skin layer formation mechanism for membranes made by dry/wet phase inversion
Authors: Pinnau Ingo , Koros William J.
Published: April 2003

Optimized membranes made by a dry/wet phase inversion process using forced‐convective evaporation consist of an ultrathin and pore‐free skin layer supported by a nodular transition layer underlying open‐cell, sponge‐like substructure. It is suggested that the out‐ermost region of such case membranes undergo phase separation by spinodal decomposition in the initial stages of the evaporation process. As a result of the small scale of phase separation present in polymer‒solvent systems, an appreciable capillary pressure occurs in the interstitial space filled with the polymer‐poor phase in contact with air. The resulting force acts normal to the membrane–air interface, which tends to consolidate the polymer‐rich phase to form a nonporous surface layer. © 1993 John Wiley & Sons, Inc.
Moduli of model elastomeric networks prepared from polymer chains having a high plateau modulus, and their interpretation in terms of the constrained‐chain model
Authors: Hsu Y.‐H. , Mark J. E. , Erman B.
Published: April 2003

High‐molecular weight polybutadiene chains having approximately 47% cis‐1,4 units and 45% trans‐1,4 units were crosslinked through their carbon‐carbon double bonds using p‐bis(dimethylsilyl) benzene as crosslinking agent and chloroplatinic acid as catalyst. This particular polymer was chosen because the high plateau modulus it exhibits in the un‐crosslinked state is taken to indicate large numbers of chain entanglements, and stress–strain measurements on such networks have frequently been interpreted with the assumption that the trapping of such entanglements during crosslinking should contribute significantly to their modull. It is shown in the present investigation that such results are equally well interpreted in terms of the new constrained‐chain theory of rubbery elasticity. © 1993 John Wiley & Sons, Inc.
Sorption of water and organic solutes in polyimide films and its effects on dielectric properties
Authors: Lim B. S. , Nowick A. S. , Lee Kang‐Wook , Viehbeck Alfred
Published: April 2003

The effect of structure on the sorption kinetics of water and of various organic solutes into polyimide (PMDA‐ODA) thin films was studied. The major techniques employed include measurements of sorption kinetics, density, and dielectric relaxation. More solute uptake, lower densities and higher diffusivities were observed for films cured at lower temperatures. By measuring both changes of mass and of density, the volume expansion of the polymer due to each solute was obtained; this was found to be proportional to the molar volume of the solute. The two dielectric relaxation peaks (denoted by γ1 and γ2) due to water (and other solutes) were studied in detail to obtain the relevant activation energies and the separate dipole moments. While water and methylene chloride appear in both γ1 and γ2 configurations, methyl and ethyl alcohol appear mainly as γ2, while acetic acid is primarily γ1. It was concluded that the γ1 configurations are relatively homogeneously distributed throughout the polymer, involving loose bonding to the polymer structure, while the γ2 configurations involve small clusters, probably chains of molecules. © 1993 John Wiley & Sons, Inc.
Physical transitions and crystallization phenomena in poly(ethylene terephthalate) studied by microhardness
Authors: Calleja F. J. Baltá , Cruz C. Santa , Asano T.
Published: April 2003

The crystallization behavior of poly(ethylene terephthalate) both with and without sodium montanate, a crystal nucleating agent, has been studied using the microhardness technique. The kinetics of crystallization from the glassy state were investigated in real time by measuring the microhardness H at different crystallization temperatures. Results are discussed in terms of the Avrami equation. Values of the Avrami exponent n of about 3 are observed for samples irrespective of nucleating agent. For samples with nucleant two crystallization ranges are observed: a first range which corresponds to a fast crystallization from nucleating agent particles and a second range which is associated with a slow self‐crystallization mode. New transitions evidenced by the presence of a small maximum in H as a function of annealing time and temperature are detected at temperatures above Tg for physically aged samples. The kinetics of this transition have also been examined. It is further shown that the presence of nucleating agent induces a hardening at room temperature which is similar to the effect produced by the physical aging of the samples below Tg. Finally, it is found that aging reduces the rate of creep of the material under the indenter. © 1993 John Wiley & Sons, Inc.
Thermal flexibility of aromatic polymide chains in solution from viscometric analysis
Authors: Lavrenko Peter N. , Okatova Olga V.
Published: April 2003

Intrinsic viscosities of poly(p‐phenylene terephthalamide) (PPTA) and poly(m‐phenylene isophthalamide) (PMIA) samples of the same molecular weight are determined in 90%, 96% and 100% sulfuric acid at temperatures from 0 to 130°C. Conditions are established under which the degree of coiling of PPTA molecule is close to that for PMIA. Experimental data are compared with the results of theoretical calculations of the Kuhn segment length. In the light of this comparison, some quantitative characteristics of the deformational flexibility mechanism for aromatic polyamide chains and the hindrance to intramolecular rotation are discussed. © 1993 John Wiley & Sons, Inc.
Solid polymers doped with rare earth metal salts. II. Thermal behavior and morphology of the neodymium acetate–poly(ethylene oxide) system
Authors: Twomey Conor J. , Chen Shaw H. , Blanton Tom , Schmid Ansgar , Marshall Kenneth L.
Published: April 2003

Samples of poly(ethylene oxide), PEO, doped with neodymium acetate, Nd (Act)3, were prepared and found to be microphase separated. At an EO/Nd (Act)3 molar ratio no less than 4, wide‐angle x‐ray diffraction (WAXD) patterns and small‐angle x‐ray scattering (SAXS) data suggest that bulk Nd (Act)3 and ionic clusters are both absent. It is inferred from differential scanning calorimetry (DSC) thermograms that in the presence of PEO, Nd (Act)3 forms an amorphous phase which is different from the amorphous phase formed by Nd (Act)3 alone. The tighter binding of CH3COO‐ to Nd3+, in comparison to Cl‐, appears to be responsible for the lack of true dissolution of Nd (Act)3 in PEO, a behavior clearly distinct from a number of polymer‐metal salt complexes reported in the literature. © 1993 John Wiley & Sons, Inc.
Multifractal analysis. A new method for the characterization of the morphology of multicomponent polymer systems
Authors: Blacher S. , Brouers F. , Fayt R. , Teyssié P.
Published: April 2003

It has been demonstrated that use of polymeric emulsifiers under usual processing conditions in the melt state is a powerful technique for preparing polymer alloys. Digitized representation of optical micrographs of thin sections of blends of a low‐density polyethylene and polystyrene (20 wt % PE‐80 wt % PS) containing 2 and 5 wt % of two hydrogenated polybutadiene‐polystyrene block copolymers exhibit different degrees of homogeneity as well as different morphological structures which can be studied by a multifractal analysis. We show how these differences are reflected in the f(α) spectrum of singularities which can be obtained by a box counting method in the canonical approximation. We have found a correlation between the f(α) curves and the mechanical properties of the corresponding samples: the samples which area the less multifractals have the best mechanical properties. © 1993 John Wiley & Sons, Inc.
FT‐Raman investigation of the thermal curing of PMDA/ODA polyamic acids
Authors: Johnson C. , Wunder S. L.
Published: April 2003

The effect of solvent on the curing reactions of PMDA/ODA polyamic acids has been investigated using Fourier transform (FT)‐Raman spectroscopy. Films of different thicknesses were cured by: (1) doctor blading 15% solids solutions onto glass slides, (2) removing all but the bound NMP, and (3) removing all the N‐methypyrrolidinone (NMP). The rate of cure and final degree of conversion of the PMDA/ODA polyamic acid to polyimide increased substantially in the presence of NMP, and this effect was attributed to the plasticizing effect of the solvent. Below a critical solvent concentration, which was estimated to be approximately 40% of the NMP concentration in the bound‐solvent limit, the rate of imidization slowed down considerably. Comparison of FT‐Raman data for PMDA/ODA polyamic acid: (1) in solution in NMP, (2) complexed with NMP in the solid state, and (3) in the solid state after all the NMP had been removed with water, indicated that intermolecular interactions were greatest in the latter case and weakest in solution. Spectra of PMDA/ODA in NMP solution provide strong evidence for binding of NMP to the amide carbonyl in solution. © 1993 John Wiley & Sons, Inc.
A hole‐filling theory of anomalous diffusion in glassy polymers. Effects of microvoids
Authors: Neogi P.
Published: April 2003

Non‐Fickian diffusion is often observed at low concentrations and without any obvious irreversible changes. This contradicts some of the predictions of the existing theories, which in general work quite well. For these cases, it is suggested that the filling of microvoids give rise to such effects. The effective diffusivity and a memory‐dependent source/sink term are obtained for describing the overall transport in heterogeneous media under local volume averaging. Some comparisons with experiments are shown. This mechanism is confined to low concentrations and supplements the existing theories which are effective at higher concentrations. © John Wiley & Sons, Inc.
A study of phase separation of crystalline and miscible polymer blends. Poly(ε‐caprolactone)/poly(styrene‐co‐acrylonitrile)
Authors: Li Wenguang , Prud'Homme Robert E.
Published: April 2003

The phase separation of a crystalline and miscible polymer blend, poly(ε‐caprolactone) /poly(styrene‐co‐acrylonitrile) (PCL/SAN), has been studied by differential scanning calorimetry (DSC), using a SAN containing 28.3% of acrylonitrile units. Several phenomena can be associated with the occurrence of phase separation depending upon the composition of the mixture. Following annealing at high temperatures, below and above the phase separation temperature Tc, three cases can be distinguished. In Case I, there is no sign of crystallization during quenching and DSC scanning, but a melting peak is observed at Tc, and above. In Case II, there is no crystallization on quenching but it does occur during the DSC run; the shift of the crystallization peak can then be related to Tc. In Case III, there is crystallization on quenching, and additional crystallization during the DSC run; the change of area of the crystallization peak is indicative of Tc. From these observations, the phase diagram of the system was determined. © 1993 John Wiley & Sons, Inc.
Determination of density changes with expansion polymerization
Authors: Millich F. , Eick J. D. , Chen G. P. , Byerley T. J. , Hellmuth E. W.
Published: April 2003

Materials that polymerize without substantial volume contraction have numerous valuable applications in dentistry and other fields. Two new symmetrical aliphatic spiro‐orthocar‐bonates, formulated from cis‐ and trans‐2‐hydroxymethyl‐cyclohexanol to give 2,3,8,9‐di(tetramethylene)‐1,5,7,11‐tetraoxaspiro [5,5] undecanes, showed, by density determinations in dilute solution, that expansion occurs with polymerization. The cis / cis‐spiroorthocarbonate racemic mixture showed a 3.9% expansion upon polymerization, and the trans/trans racemic mixture showed a 3.5% expansion. The densities were determined by pycnometry, with a precision reliable to at least four figures. This method is thus recommended for cases of soluble monomer/polymer pairs for which the density difference will be small and where the partial specific volumes are independent of concentration, thereby avoiding the complexities of variable physical states of monomer and/or polymer. © 1993 John Wiley & Sons, Inc.
Whiskers of poly(3‐alkylthiophene)s
Authors: Ihn Kyo Jin , Moulton Jeff , Smith Paul
Published: April 2003

It is shown that poly(3‐alkylthiophene)s may readily crystallize from poor solvents in the form of whiskers. The experimental conditions required for the formation of whiskers were found to depend upon the alkyl side‐chain length, solvent quality, and temperature. In all cases studied for alkyl side‐chain lengths of 3‐12 carbon atoms, the widths of the whiskers were of the order of 15nm, while their lengths often exceeded tens of microns. The thickness of the whiskers formed under the experimental conditions employed was found to scale with side‐chain length, and was approximately 2 or 3 times the a/2 lattice dimension of the polymer unit cell. Packing of the macromolecules within the whiskers was such that the polymer backbones were normal to the whisker length; that is, the b‐axis was oriented parallel to the long axis of the whiskers. These results are thought to be relevant to known thermochromism phenomena associated with poly(3‐alkylthiophene)s. © 1993 John Wiley & Sons, Inc.
The effect of drawing on the transport of gases through polyethylene
Authors: Webb J. A. , Bower D. I. , Ward I. M. , Cardew P. T.
Published: April 2003

A study has been made of the gas transport properties of polyethylene films of two different grades, Hizex 7000F and Rigidex 002‐55, one‐way drawn at 115°C to draw ratios in the range 1–20. Measurements of the permeability and diffusion coefficients of helium, oxygen, carbon dioxide and nitrogen have been made with a dynamic flow rate technique, utilizing a mass spectrometer detection system, and of oxygen using a commercial OXTRAN system. The samples were characterized by the measurement of density, birefringence and modulus and by wide‐angle x‐ray diffraction and differential scanning calorimetry. There is a large decrease in both the permeability and diffusion coefficients for all gases with increasing polymer draw ratio, with up to an 80‐fold decrease in permeability for the larger permeants compared with the 10‐fold decrease observed for helium. The solubilities of all the gases decrease only by a factor of ∼ 2. The diffusion results are discussed in terms of geometric impedance and chain immobilization factors. The solubilities, on the other hand, appear to relate primarily to the amorphous volume fraction of the polymer. © 1993 John Wiley & Sons, Inc.
Tensile yield of polyethylene in relation to crystal thickness
Authors: Darras O. , Séguéla R.
Published: April 2003

Tensile yield stress measurements have been performed on a serie of four ethylene/1‐butene copolymers covering the crystallinity range 0.33–0.74. Samples have been prepared from melt‐crystallization and from solution‐crystallization at various concentrations in decalin in order to span a wide range of crystal thickness. It is shown that tensile yield stress depends on crystal thickness rather than on crystallinity. This result is perfectly consistent with a plasticity model based on the nucleation of dislocations. Besides, it in‐dicates that the main role of the amorphous phase is only to transmit the load upon the crystals, irrespective of its proportion. The yield stress dependence on crystallinity reported previously relies on the direct correlation of crystal thickness and crystallinity, in the case of melt‐crystallized samples only. Discrepancies with the model are amply discussed. © 1993 John Wiley & Sons, Inc.
An investigation of the smectic‐isotropic transition in a side‐chain liquid crystal polymer by synchrotron radiation x‐ray diffraction
Authors: Galli G. , Mcnamee S. G. , Ober C. K.
Published: April 2003

In this work we have used synchrotron x‐radiation diffraction to follow in real‐time the isotropic‐smoetic phase transition of a side‐chain liquid crystalline polymer. The analysis of the x‐ray data indicated that the transition occurs within a very narrow biphasic region. As the transition takes place, the size of the smectic regions, as indicated by the width of the diffraction peaks, changed only very slightly before impingement, suggesting a two‐dimensional growth pattern. A thermal investigation of the polymer paralleling the x‐ray experiments was undertaken and a kinetic analysis applied to the resulting data. Qualitative agreement with a disk‐like growth of the smectic regions was found. We have shown that the overall kinetics of the isotropic‐smectic transition of a side‐chain polymer can be studied by x‐ray diffraction permitting the evaluation of several structural parameters. © 1993 John Wiley & Sons, Inc.
An experimental and theoretical study of the PVT equation of state of butadiene and isoprene elastomers to 200°C and 200 MPa
Authors: Yi Y. X. , Zoller P.
Published: April 2003

We have performed and analyzed extensive pressure‐volume‐temperature (PVT) measurements on uncrosslinked polybutadiene and polyisoprene elastomers from ambient temperature to about 200°C and 200 MPa. In the polybutadiene series, 1,2 content varied from 8 to 87%, the remainder being similar amounts of cis‐1,4 and trans‐1,4. In the polyisoprene series the 3,4 content varied from 8 to 64%, the trans‐1,4 content was 12–16%, and the remainder was cis‐1,4, with < 4% 1,2 content. We report parameters describing the experimental data in terms of the empirical Tait equation, the cell model, the Simha‐Som‐cynsky equation, the Sanchez‐Lacombe, and the Flory‐Orwoll‐Vrij models. In general the parameters show systematic changes with the microstructure content. The agreement between theory and experiment is excellent for the Tait equation, and also for the Simha‐Somcynsky model and the cell model. The maximum deviation between theory and experiment was less than 0.004 cm3/g for the Simha‐Somcynsky theory, and less than 0.005 cm3/g for the cell model. Average absolute deviations are three to four times less. For the Sanchez‐Lacombe and the Flory‐Orwoll‐Vrij models, the maximum deviations are 5–8 times as large, and very systematic. Parameter derived from the Simha‐Somcynsky theory are discussed with respect to the microstructure, and with respect to the glass transition of these two series of materials. © 1993 John Wiley & Sons, Inc.
Orientational–deformational nature of flow birefringence in solutions of rigid‐chain polymers
Authors: Pogodina N. V.
Published: April 2003

The orientational–deformational nature of flow birefringence (FB) in solutions of rigid‐chain polymers is confirmed experimentally. The possibility of a direct determination of the internal viscosity parameter by the dependence of the FB relaxation time on the solvent viscosity is demonstrated. Indirect manifestation of internal viscosity in the FB relaxation time is confirmed by the dependence of the form factor on the degree of coiling. © 1993 John Wiley & Sons, Inc.
Increase in dynamic modulus of nylon 6 fiber in repeated heating and cooling cycles under sinusoidal deformation
Authors: Kunugi Toshio , Suzuki Akihiro , Chida Kimitaka
Published: April 2003

The repeated heating and cooling cycles under sinusoidal deformation have been investigated on nylon 6 fibers. The fibers zone‐drawn twice at high temperatures were used, which have a crystallinity of 52.2% and a birefringence of 59.4×10−3. The heating and cooling cycle was performed twice at a frequency of 110 Hz over a temperature range from 0°C to 180°C and 190°C. The crystallinity and birefringence of the treated fiber were 51.7% and 60.7×10−3, respectively, indicating almost no changes in molecular orientation and crystallinity. However, the dynamic modulus, E′, increased steadily over whole temperature range measured. Finally, the E′ value reached 21 GPa at room temperature and 10 GPa ever at 180°C. The elongation of fiber after two cycles was only about 5%. © 1993 John Wiley & Sons, Inc.
Electron paramagnetic resonance spectroscopic studies of thermally generated free radicals in PMR‐15 polyimide resins
Authors: Ahn Myong K. , Stringfellow Thomas C. , Fasano Matthew , Bowles Kenneth J. , Meador Michael A.
Published: April 2003

PMR‐15 is a high‐performance thermoset polyimide resin that is used in many high‐temperature applications. Postcured PMR‐15 produces room‐temperature electron paramagnetic resonance (EPR) spectra from stable freeradical species that are formed during the postcuring stages. The variable‐temperature EPR spectral intensities show a minimum at Tmin in the range −60 to −40°C, and a maximum at Tmax in the range 80–120°C. The EPR intensities follow the inverse temperature dependence of Curie's law below Tmin and are due to a stable free radical. The intensities then increase with increasing temperature between Tmin and Tmax. The free radical with such temperature dependence is not present below Tmin and is undetectable by EPR at temperatures above Tmax. These free radicals are generated during the postcuring process at elevated temperature above 310°C. The thermo‐oxidative degradation involves free radicals generated during the postcuring process in the presence of oxygen gas. © 1993 John Wiley & Sons, Inc.
A bimodal structure of solution‐grown isotactic polypropylene with orthogonally crossed lamellae
Authors: Masada Isao , Okihara Takumi , Murakami Shozo , Ohara Masayoshi , Kawaguchi Akiyoshi , Katayama Ken‐Ichi
Published: April 2003

Isotactic polypropylene (iPP) was crystallized from solution on a uniaxially‐oriented iPP film. Small‐angle x‐ray scattering patterns obtained from the sample showed two perpendicularly crossed lameliae 9.3 nm thick that overgrew flat‐on and edge‐on on the substrate. In the through wide‐angel x‐ray diffraction pattern (taken with incident x‐rays normal to the iPP film surface), strong hkO reflections were arranged in an hkO net pattern indicating that the a‐axis of the monoclinic α unit cell was oriented parallel to the chain direction of the substrate. From this, it was concluded that the flat‐on lamellae grew with the a‐axis parallel to the chain axis of the substrate and with the b‐axis parallel to its surface. In the edge wide‐angle x‐ray diffraction pattern (X‐rays incident on the edge of the film), arced, strong 110 and 220 reflections from overgrown crystals were observed on the equator of the fiber pattern of the substrate. This indicated that the edge‐on lamellae epitaxially grew with the c‐axis aligned parallel to the chain axis of the substrate. The homoepitaxy explains the correlated growth mode between the orthogonally crossed lamellae: they grew epitaxially, the a‐axis of one lamella coinciding with the c‐axis of the other and the {010} planes in contact. © 1993 John Wiley & Sons, Inc.
Multiphase structure of segmented polyurethanes: Its relation with spherulite structure
Authors: Li Yingjie , Liu Jian , Yang Huichang , Ma Dezhu , Chu Benjamin
Published: April 2003

Small‐angle light‐scattering (SALS), Polarized light microscopy (PLM), differntial scanning calorimetry (DSC), and small‐angle x‐ray scattering (SAXS) were used to study morphological changes in segmented polyurethanes with 4,4′‐diphenylmethane diisocyanate (MDI) and 1,4‐butanediol (BD) as the hard segment. It was found. for the first time, that spherulites could form from the melt by quenching the polyurethanes in the melt state to annealing temperatures between 120°C and Th, the highest annealing temperature for spherulite formation. Th ranged from 140°C to ca. 170°C and depended upon the hard‐and soft‐segment compatibility. Within the range 120°C to Th, the radius of the spherulite increased with increasing hard‐segment content at each fixed annealing temperature. Annealing at 135–140°C gave rise to the largest spherulites. SAXS was used to investigate the phase‐separated structures corresponding to the spherulite formation. The interdomain spacing increased with increasing hard‐segment content and with increasing annealing temperature.The degree of phase separation first increased with increasing annealing temperature from room temperatures (ca. 25°C), reached a maximum at ca. 107°C, and then decreased with further increase in the annealing temperature. On the basis of these observations, the mechanisms of phase separation, crystallization, and spherulite formation are discussed. © 1993 John Wiley & Sons, Inc.
Optimization of asymmetric permeation in heterogeneous composite membranes
Authors: Yamanaka Tadae
Published: April 2003

Asymmetric permeation in two‐phase composite membranes with heterogeneous structures represented by a one‐dimensional distribution of composition is treated theoretically on the basis of an irreversible thermodynamic transport equation. It is assumed that the permeability of one of the component phases is a monotone function of the activity of permeant while that of the other phase is constant, and that the permeability of the composite membrane is given by the volume average of the resistance coefficient, which is the inverse of permeability. Under these assumptions, it is shown that the optimal membrane which maximizes the degree of asymmetric permeation reduces to a binary laminate membrane. The condition for constructing the optimal laminate membrane is obtained explicitly. Conversely a condition on a desirable membrane component which realizes an arbitrary degree of asymmetric permeation is presented. These results can be applied to the optimal design of a membrane valve which is a chemical analog of a diode. © 1993 John Wiley & Sons, Inc.
The effect of vacuum‐ultraviolet laser wavelengths on the surface treatment of polyolefinic polymers
Authors: Kesting Wolfgang , Bahners Thomas , Schollmeyer Eckhard
Published: April 2003

The laser‐induced modification of the surface morphology of poly(propylene) fibers and films was investigated. It is known that strongly absorbing fibers such as poly(ethylene terephthalate) and polyamide obtain characteristic surface morphologies after treatment with 193 or 248 nm laser irradiation. Polyolefinic material cannot be modified directly (i.e., without doping) by irradiation with these wavelengths. Therefore experiments were carried out using a 157 nm F2‐laser. After irradiation in a vacuum chamber at fluences in excess of 50 mJ/cm2 poly(propylene) also reveals the well‐known surface morphology. Compared with aromatic polymers a rather high number of pulses is needed to generate the effect. © 1993 John Wiley & Sons, Inc.
Glass transition, crystallization, and morphology relationships in miscible poly(aryl ether ketones) and poly(ether imide) blends
Authors: Hsiao Benjamin S. , Sauer Bryan B.
Published: April 2003

The relationships among glass transition, crystallization, melting, and crystal morphology of poly(aryl ether ketone) (PAEK)/poly(other imide) (PEI) blends was studied by thermal, optical and small‐angle x‐ray scattering (SAXS) methods. Two types of PAEK were chosen for this work: poly(aryl ether ether ketone), PEEK, and poly(aryl ether ketone ketone), PEKK, which have distinctly different crystallization rates. Both PAEKs show complete miscibility with PEI in the amorphous phase. As PAEK crystallizes, the noncrystallizable PEI component is rejected from the crystalline region, resulting in a broad amorphous population, which was indicated by the broadening and the increase of Tg over that of the purely amorphous mixture. The presence of the PEI component significantly decreases the bulk crystallization and crystal growth rate of PAEK, but the equilibrium melting temperature and crystal surface free energies are not affected. The morphology of the PEI segregation was investigated by SAXS measurements. The results indicated that the inter(lamellar‐bundle) PEI trapping morphology was dominant in the PEEK/PEI blends under rapid crystallization conditions, whereas the interspherulitic morphology was dominant in the slow crystallizing PEKK/PEI blends. These morphologies were qualitatively explained by the expression δ=D/G, where G was the crystal growth rate and D was the mutual diffusion coefficient. © 1993 John Wiley & Sons, Inc.
Structure/permeability relationships of polyimides with branched or extended diamine moieties
Authors: Stern S. A. , Liu Y. , Feld W. A.
Published: April 2003

Mean permeability coefficients for CO2, O2, N2, and CH4 in seven types of 6FDA polyimides with branched or extended diamine moieties were determined at 35.0°C (95.0°F) and at pressures up to 10.5 atm (155 psia). In addition, solubility coefficients for CO2, O2, N2, and CH4 in six of these polyimides were determined at 35.0°C and at 6.8 atm (100 psia). Mean diffusion coefficients for the six gas/polyimide systems were calculated from the permeability and solubility data. The relationships between the chemical structure of the polyimides, some of their physical properties (glass transition temperature, mean interchain spacing, specific free volume), and their gas permeability, diffusivity, and solubility behavior are discussed. The 6FDA polyimides studied here exhibit a considerably lower selectivity for the CO2/CH4 and O2/N2 gas pairs than 6FDA polyimides with short and stiff aromatic diamines with comparable CO2 and O2 permeabilities. © 1993 John Wiley & Sons, Inc.
Rotor‐synchronized two‐dimensional 13C CP/MAS NMR studies of the orientational order of polymers. I. High‐performance ultrahigh molecular weight polyethylene fibers
Authors: Tzou D. L. , Huang T. H. , Desai P. , Abhiraman A. S.
Published: April 2003

The orientational order of three morphological components, identified previously as two crystalline components, C1 and C2, and an amorphous component, A of four polyethylene fibers, including two gelspun ultrahigh molecular weight (PE‐I and PE‐II) and two meltspun moderate molecular weight (PE‐D and PE) polyethylene fibers are further analyzed by rotor‐synchronized two‐dimensional 13C CP/MAS (ROSMAS) nuclear magnetic resonance (NMR) techniques. Our results indicate that the orientational order of these components differ substantially among themselves in a given fiber and among different fibers of the same component. Values of β1/2, the polar angle at which the orientational distribution function (ODF) P 〈β〉 decays to half its maximum, are determined to be: 18° (C2 of PE‐II), 21° (C2 of PE‐I), 29° (C2 of PE‐D), 31° (C1 of PE‐I) and 50° (C2 of PE). No orientational sideband can be detected for component A, suggesting that the A component is due to the amorphous domain. The implication of this results and the technical limit of this technique are analyzed. © 1993 John Wiley & Sons, Inc.
Intramolecular interactions in poly(styrene‐co‐acrylonitrile)/poly(ε‐caprolactone) blends
Authors: Janarthanan V. , Kressler J. , Karasaz F. E. , Macknight W. J.
Published: April 2003

Specific interactions in blends of poly(ε‐caprolactone) (PCL) and poly(styrene‐co‐acry‐lonitrile) (SAN) were studied as a function of copolymer composition and blend ratio by using Fourier‐transform infrared spectroscopy (FTIR). It was shown that miscibility occurred within a certain range of copolymer compositions because the presence of PCL reduced the thermodynamically unfavorable repulsion between styrene and acrylonitrile segments in the random copolymer. This effect was observed in terms of a shift to higher frequencies in the 700 cm‐1 γ‐CH out‐of‐plane deformation vibration absorption of styrene and in the approximately 2236 cm−1 CN stretching frequency band in acrylonitrile segments. Specific intermolecular interactions between SAN and PCL were not observed in this study. © 1993 John Wiley & Sons, Inc.
Birefringence in polycarbonate: Molecular orientation induced by cooling stresses. II. Effects of sectioning
Authors: Wimberger‐Friedl R. , De Bruin J. G.
Published: April 2003

Birefringence distributions in cross‐sections of quenched polycarbonate disks are investigated. The effects of the introduction of new surfaces by sectioning are studied by using different cross‐section widths, by quenching rod‐shaped specimens, and by measuring the birefringence with oblique incident light. The experimental results are confirmed by numerical calculations of stress distributions in rods with varying aspect ratios. Stress release by appropriate sectioning is used to distinguish between stress and orientation contribution to birefringence. It is found that cutting cross‐sections leads to a major stress redistribution in the width direction. This does not affect the birefringence measurement, but the decrease of the stress level in the long direction needs to be taken into account. The molecular orientation in the quenched samples cannot be explained only by the effect of transient thermal stresses above the glass transition. There is another orientation contribution, most likely related to stress relaxation below Tg. © 1993 John Wiley & Sons, Inc.
Miscibility of a polyarylate with a liquid crystalline copolyester
Authors: Wang Li‐Hui , Porter Roger S.
Published: April 2003

The miscibility has been investigated for binary blends of a polyarylate (PAr) with a liquid crystalline copolyester of p‐hydroxybenzoate and ethylene terephthalate units in a 6/4 molar ratio (PET/PHB). The binary blends were prepared by solution precipitation. The transitions of the PET/PHB have been measured with a rheometrics dynamic spectrometer. The phases in blends have been studied with a differential scanning calorimeter, by ther‐mogravimetry and with a polarizing optical microscope. The blends exhibit two glass transitions (Tgs) over the composition range 10–90 wt %. The amorphous PET phase from the PET‐PHB is found to be partially miscible with PAr, which leads to a decrease of the PAr Tg. The amount of this partially miscible portion of PET has been estimated by the Couch‐man equation. On heat treatment of the blends at 250 to 300°C, transesterficiation takes place, as judged by the shift of the higher of the two Tgs. © 1993 John Wiley & Sons, Inc.
Charge‐mosaic membrane from gamma‐irradiated poly(styrene‐butadiene‐4‐vinylpyridine) triblock copolymer
Authors: Liang Liang , Ying Shengkang
Published: April 2003

Poly(styrene‐butadiene‐4‐vinylpyridine) triblock copolymers were prepared from styrene (S), butadiene (B), and 4‐vinylpyridine (P) by sequential anionic polymerization with n‐butyllithium as initiator and benzene as solvent. The triblock copolymer was characterizated by gel‐permeation chromatography (GPC), transmission electron microscopy (TEM), and viscoelastic spectrometry. Films of the triblock copolymer cast from solution in mixtures of chloroform and n‐butyraldehyde were subjected to gamma‐ray irradiation to form cross‐linked networks, Cationic and anionic groups were introduced by sulfonation and quater‐nization to obtain charge‐mosaic membranes. The resulting membrane had substantial cation‐exchange and anion‐exchange capacities. The membranes were very permeable to electrolyte (JKCI = 2.10×10−8 mol/cm2 s). © 1993 John Wiley & Sons, Inc.
Orientation distribution of liquid‐crystalline polyester sheets studied by polarized infrared spectroscopy
Authors: Kaito Akira , Kyotani Mutsumasa , Nakayama Kazuo
Published: April 2003

Polarized infrared spectroscopy was applied to evaluate the orientation distribution in extrusion‐molded sheets of a liquid‐crystalline copolyester consisting of 73 mol % of 4‐hydroxy benzoic acid units and 27 mol % of 2‐hydroxy‐6‐naphthoic acid units. The surface orientation function was evaluated from the polarized attenuated total reflection/Fourier transform infrared spectra and the polarized specular reflection spectra. In the case of the specular reflection method, the absorption and refractive indices were obtained from the specular reflectance using the Kramers–Kronig relation and the Fresnel equation. On the other hand, the microscopic orientation functions inside the sheets were evaluated by Fourier‐transform infrared microspectroscopy. The polarized FTIR microspectra of microtomed section of sheets were measured in a microscopic domain as small as 40 μ at various positions from the center of the sheet. The surface orientation function was shown to be higher than the interior orientation function. Orientation functions obtained by the spectroscopic techniques are lower than crystal orientation functions determined by wide‐angle x‐ray diffraction, implying that the crystal orientation function is higher than the orientation function of noncrystalline molecular chains. The orientation distribution in the sheet is discussed in relation to the morphological structures studied by scanning electron microscopy. © John Wiley & Sons, Inc.
Small‐angle x‐ray scattering of distorted lamellar structures
Authors: Sasanuma Yuji , Abe Akihiro , Sasanuma Takako , Kitano Yukishige , Ishitani Akira
Published: April 2003

Small‐angle x‐ray scattering (SAXS) intensity for the lamellar structure of polymeric materials has been formulated with consideration of structural defects such as the finiteness of the lamellar stack, the lamellar bend, and the paracrystalline distortions. In particular, the effects of the lamellar bend on the SAXS profile have been elucidated on the basis of Vonk'xss formula γ1(x) – γ(x)exp(−2x/d). Here, the scattering profile due to the lamellar bend is shown to be expressed by a Cauchy function. The integral breadth is equal to 2π/d, being independent of the order of scattering. As an example of the SAXS analysis based on the theory, the characterization of the lamellar structure in the “hard” elastic polypropylene films is reported. The long period and the lamellar thickness are evaluated from the correlation function, and the distortion length and Hosemann's g factor are estimated according to the procedure presented here. On the basis of these structural parameters, the relationship between the manufacturing process and the lamellar structure of the polypropylene films is discussed. © 1993 John Wiley & Sons, Inc.
Characterization of amorphous carbon films by 13C CP MAS NMR spectroscopy
Authors: Beamson G. , Brennan W. J. , Clayden N. J. , Jennings R. C. K.
Published: April 2003

13C CP MAS NMR spectroscopy was used to characterize α‐C:H materials generated from methane and hydrogen mixtures using a microwave plasma. Dipolar dephasing experiments indicate a range of Tdd making quantification of quaternary “diamond”‐like carbons difficult. Unconstrained lineshape analysis is not suitable for the deconvolution of the NMR spectra, but linewidth constrained analyses gave reasonable results. © 1993 John Wiley & Sons, Inc.
Studies on solution cast perfluorocarbonsulfonic acid ionomers
Authors: Tsatsas A. T. , Risen W. M.
Published: April 2003

The thermal properties of perfluorocarbonsulfonic acid ionomer films cast from solution and their temperature‐dependent far infrared spectra have been investigated. In addition to the endotherms and spectral changes associated with the loss of solvent as the films were heated, a significant exotherm has been observed and assigned to the relaxation associated with rearrangements resulting in partially crystallized phases in insoluble thermally treated membranes. © 1993 John Wiley & Sons, Inc.
The morphology of poly(vinylidene fluoride) crystallized from blends of poly(vinylidene fluoride) and poly(ethyl acrylate)
Authors: Briber Robert M. , Khoury F.
Published: April 2003

A combined optical and electron microscopical study has been carried out of the crystallization habits of poly(vinylidene fluoride) (PVF2) when it is crystallized from blends with noncrystallizable poly(ethyl acrylate) (PEA). The PVF2/PEA weight ratios were 0.5/99.5,5/95, and 15/85. Isothermal crystallization upon cooling the blends from the single‐phase liquid region was carried out in the range 135–155°C, in which the polymer crystallizes in the α‐orthorhombic unit cell form. The 0.5/99.5 blend yielded multilayered and planar lamellar crystals. The lamellae formed at low undercoolings were lozenge shaped and bounded laterally by {110} faces. This habit is prototypical of the dendritic lateral habits exhibited by the crystals grown from the same blend at high undercoolings as well as by the constituent lamellae in the incipient spherulitic aggregates and banded spherulites that formed from the 5/95 and the 15/85 blends, respectively. In contrast with the planar crystals grown from the 0.5/99.5 blend, the formation of the aggregates grown from the 5/95 blend is governed by a conformationally complex motif of dendritic lamellar growth and proliferation. The development of these aggregates is characterized by the twisting of the orientation of lamellae about their preferential b‐axis direction of growth, coupled with a fan‐like splaying or spreading of lamellae about that axis. The radial growth in the banded spherulites formed from the 15/85 blend is governed by a radially periodic repetition of a similar lamellar twisting/fan‐like spreading growth motif whose recurrence corresponds to the extinction band spacing. This motif differs in its fan‐like splaying component from banding due to just a helicoidal twisting of lamellae about the radial direction. © 1993 John Wiley & Sons, Inc.
Coionomeric mixtures of polyhydroxyethers and ethylene methacrylic acid copolymers. I. Effects of cation concentration and ABA oligomeric miscibilisers on morphology and properties
Authors: Mascia L. , Moggi A.
Published: April 2003

Mixtures of a phenoxy polymer (polyhydroxyether of bis‐phenol A) and a polyolefin ionomer (sodium ionomer of ethylene methacrylic acid copolymer) were compatibilized by the addition of small amounts of sodium ethoxide and/or by the incorporation of varying amounts of A‐B‐A block oligomers. The latter were produced by reacting several bis‐phenol A epoxy resins, varying in molecular weight, with montanic acid in order to provide segments soluble in each of the two polymer components of the blend. Chemical miscibilization by the addition of sodium ethoxide changed the morphology into one containing larger amounts of cocontinuous phases, while the incorporation of substantial amounts of A‐B‐A oligomer brought about primarily the formation of irregular and highly elongated particles. The mixtures were found to exhibit the typical properties of ionomers which were enhanced by the addition of sodium ethoxide. Furthermore sufficient evidence was gathered to establish that the ionomeric aggregates are shared by both polymer components of the blend, from which the term coionomeric mixture is derived. © 1993 John Wiley & Sons, Inc.
Structure and melting of perfectly alternating ethylene‐carbon monoxide copolymers
Authors: Lommerts B. J. , Klop E. A. , Aerts J.
Published: April 2003

The perfectly alternating ethylene carbon monoxide copolymer (polyketone; POK) has been studied by means of 1H nuclear magnetic resonance and thermal analysis, and the crystal structure, determined by wide angle x‐ray scattering methods, is presented. The crystal structure of this polymer in well‐oriented fibers (POK‐α) is as follows: Space group Pbnm, α = 6.91 (2) Aå, b = 5.12 (2) Aå, c = 7.60 (3) Aå (fiber axis), pc = 1383 kg/m3. This differs from the structure reported earlier by Chatani et al. (POK‐β). The very dense packing in the POK‐α structure is a result of the arrangement of the dipoles in the crystal lattice, giving rise to strong lateral forces between the polymer chains. Owing to the all‐trans conformation of the polymer chain in the crystal lattice, high moduli can be achieved for well‐oriented fibers. A first approximation results in a value of 360 GPa for the theoretical modulus. From the melting data for a series of low molecular weight polyketone homologs, a first, estimate is derived for the crystalline heat of fusion (215–330 J/g) for infinite chain length. As a result of the strong lateral forces, this polymer shows a (very) high crystalline heat of fusion, whereas creep and compressive strength of oriented fibers are expected to be superior to those of high‐modulus polyethylene fibers. © 1993 John Wiley & Sons, Inc.