bluuebunny/crossref_metadata_2025 huggingface dataset:
Gas sorption and transport properties of bisphenol‐I‐polycarbonate
Authors: Hägg M.‐B. , Koros W. J. , Schmidhauser J. C.
Published: April 2003

Gas sorption and transport characterization of a new polymer in the polycarbonate family, based on the bisphenol of 3,3,5‐trimethylcyclohexane‐1‐one (BPI) is reported at 35°C. By comparison with properties of other known polycarbonates, the effects of inhibition of both packing and segmental motion due to the introduction of the bulky substituent in the backbone are elucidated. The Tg of the material was measured with differential scanning calorimeter (DSC) and was found to be unusually high for a polycarbonate (233°C). This indicates a successful inhibition of the large‐scale segmental mobility of the polymer. Variable 13C NMR analysis indicated that rotation of one phenylene ring has an unusually high (ca. 10 kcal) energy barrier, whereas the other phenylene ring has a more typical rotation profile (barrier < 3 kcal). The density was measured and found to be low (1.107 g/cm3), indicating a high fractional free volume (FFV) for the polymer. Consistent with expectations, the introduction of the bulky‐substituted cyclohexane group gave high permeabilities for the various gases tested (N2, O2, He, CH4, CO2) compared to most standard polycarbonates. On the other hand, the permselectivities were typical for standard polycarbonates. The solubility coefficients of all gases were rather high, as expected for a polymer with such an open structure. © 1994 John Wiley & Sons, Inc.
Charge transport in poly(methylphenylsilane): The case for superimposed disorder and polaron effects
Authors: Bässler H. , Borsenberger P. M. , Perry R. J.
Published: April 2003

Careful analysis of the temperature dependence of the hole mobility in poly (methylphenylsilane) indicates that the functional dependence is between an Arrhenius law and a ln μ ∝ T−2 law as predicted by a model of disorder‐controlled hopping. This is attributed to the superposition of disorder and polaron effects. A method is presented for separating the two contributions. The evolution of time‐of‐flight photocurrent transients with decreasing temperature is consistent with the disorder parameter derived from the temperature dependence of the mobility. © 1994 John Wiley & Sons, Inc.
An NMR study of segmental motion in poly(isobutylene) and the relationship to translational diffusion of sorbed CO2
Authors: Bandis Athinodoros , Wen Wen‐Yang , Jones Elliot B. , Kaskan Peter , Zhu Yong , Jones Alan A. , Inglefield Paul T. , Bendler John T.
Published: April 2003

The spin‐lattice relaxation times as well as nuclear Overhauser enhancements (NOE) are determined for the methylene carbon of polyisobutylene (PIB). Three different correlation functions are used to treat the relaxation data to describe the local motion of the PIB backbone rubber. The first is the Hall‐Helfand function combined with restricted anisotropic rotational diffusion, the second is the Dejean‐Lauprêtre‐Monnerie function, and the third is the Williams‐Watts function combined with restricted anisotropic rotational diffusion. Spin‐lattice relaxation times are also determined on PIB under pressure of CO2 gas to check for changes in segmental motion in the presence of this penetrant. All the models give a satisfactory description for the local dynamics of the backbone carbon of the polymer chain, yielding comparable values for the time scale of conformational changes, apparent activation energies and distribution of correlation times. In addition, a proton line shape experiment is performed on bulk PIB as a function of temperature. The results are interpreted in terms of two motional components in the polymer chains: fast and slow ones. Applying a revised version of Rössler's formalism to our data, an average energy barrier is found which is consistent with the apparent activation energies. The apparent activation energy obtained for PIB, from the nuclear magnetic resonance (NMR) measurements, about 35 kJ, is slightly higher than the apparent activation energy for the translational diffusion of CO2 in PIB from NMR data. The distribution of correlation times and the correlation times themselves for segmental motion of the PIB and translational diffusion of CO2 in PIB are very similar, indicating a close link between the two motional processes. The distribution of correlation times is close to a single exponential in PIB consistent with Angell characterization of this material as a strong liquid. © 1994 John Wiley & Sons, Inc.
Tailored adhesion at polymer/nonpolymer interfaces
Authors: Smith Joshua W. , Kramer Edward J. , Mills Peter J.
Published: April 2003

In this investigation, block copolymers of deuterated polystyrene (dPS) and poly (2‐vinylpyridine) (PVP) have been used to modify the adhesion at polystyrene/soda lime glass interfaces. The fracture energy, Gs of these interfaces was measured using an asymmetric double cantilever beam specimen. The failure mechanism was investigated using forward recoil spectrometry (FRES) and Rutherford backscattering spectrometry (RBS). The areal density, ∑ of the dPS‐PVP block copolymer at the two fracture surfaces, as well as the fraction of the dPS block on the PS side of the fractured sample are measured directly by FRES. The fraction of the PVP block on the glass side of the interface can be found by quaternizing the PVP with methyl iodide and then using RBS to measure the amount of iodine on each fracture surface. Short dPS blocks (NdPS < 175) do not entangle effectively with the PS homopolymer and only very small increases in Gc can be achieved as the dPS block pulls out of the interface. If the dPS block is long (NdPS ≫ 175) and if ∑ is large, crazes can develop in the PS ahead of the crack. The crazed interface fails at low ∑ by breaking the block copolymer close to the styrene/vinylpyridine link. At higher ∑, if the PVP block is relatively short (NPVP = 95), the crazed interface fails by the PVP block being pulled off the glass. If both the PVP and dPS blocks are long (≫ 175), the Gc increases rapidly with increases in ∑, but the interface becomes so strong that the glass on the thinner side of the test specimen breaks. The dPS block and the PVP block are found on opposite sides of the fracture surface with most of the PVP on the glass and most of the dPS on the PS side of the interfaces. Finally, if the glass surface is modified by coating it with a self‐assembled hydrophobic monolayer produced from chlorodimethyloctadecylsilane (CDMOS), the interface becomes very weak and fails by pull‐off of the PVP from the CDMOS‐coated glass. Using these results it is possible to tailor the interfacial adhesion to produce a desired Gc within a wide range of possible values. © 1994 John Wiley & Sons, Inc.
Temperature‐dependent dielectric studies of fully cured diethylene glycol bis (allyl carbonate)
Authors: DeMeuse Mark T.
Published: April 2003

Studies are presented of the dielectric properties of fully cured diethylene glycol bis (allyl carbonate) as a function of both frequency and temperature. It is shown that the characteristics of the fully cured system are dominated by a localized, secondary transition that is associated with motion of the carbonate unit. The glass transition is shown to contribute little to the dielectric properties within the temperature range 20–70°C. © 1994 John Wiley & Sons, Inc.
Estimation of interaction energies by the critical molecular weight method: 1. Blends with polycarbonates
Authors: Callaghan T. A. , Paul D. R.
Published: April 2003

The interaction energies between PS, Pα‐MS, and PMMA with several bisphenol‐A‐based polycarbonates were quantitatively determined from oligomer/oligomer, oligomer/homopolymer, and homopolymer/copolymer blends. Interaction energies were calculated from the Flory‐Huggins theory and the Sanchez‐Lacombe equation of state theory using experimental cloud points or miscibility boundaries. Alkyl addition to the phenyl rings of polycarbonate is favorable for miscibility with polystyrene whereas halogenation of the bisphenol connector unit is favorable for miscibility with poly(methyl methacrylate). Interaction energies are quantitatively ranked and described qualitatively in terms of changes in the electronic charge distribution of the polymer repeat units as calculated by SYBYL software. © 1994 John Wiley & Sons, Inc.
Depth‐profiling of polymer laminates using fourier transform infrared (ATR) spectroscopy: The barrier film technique
Authors: Pereira Marcia R. , Yarwood Jack
Published: April 2003

We report FTIR‐ATR spectra of a polymer laminate (PMMA/PVOH) at different base layer thicknesses and different angles of incidence on a ZnSe substrate. By varying this ‘barrier’ layer (of PMMA) we have demonstrated that different effective penetration depths into the PVOH are achieved, in very good agreement with the calculated electric fields as a function of distance away from the substrate surface. Such work forms the basis for depth profiling measurements in order to detect interfacial interactions between the polymer molecules. © 1994 John Wiley & Sons, Inc.
A generalization of dual mode transport theory for glassy polymers
Authors: Horas Jorge A. , Nieto F.
Published: April 2003

The polymer matrix, divided in a number of cells in which the penetrant molecules can be sorbed and migrate, is considered. Each cell has been assigned an effective energy value that obeys a particular distribution. The effective diffusion coefficient and its concentration and temperature dependence are determined. The origin of sorbed penetrant mobility is studied. Using a delta‐Dirac distribution for the site's energetic values, the model is reduced in the appropriate limit (low pressure) to other formulations of the dual transport model. More general results, allowing the site's energetic values to be drawn from a Gaussian distribution, are also given. © 1994 John Wiley & Sons, Inc.
Thermal diffusivity and electrical conductivity of electropolymerized polypyrrole films
Authors: Tsutsumi Naoto , Ishida Satoshi , Kiyotsukuri Tsuyoshi
Published: April 2003

This article presents measurement of thermal diffusivity and electrical conductivity of polypyrrole films prepared by electropolymerization. Thermal diffusivity was measured by laser radiometry (former flash radiometry). Electrical conductivity was determined by a conventional four‐probe method. Increase of thermal diffusivity is observed when increasing the supporting electrolyte concentration, which is also shared with the increase of electrical conductivity. Both thermal diffusivity and electrical conductivity significantly depended on the types of counter anion incorporating into polymer bulk. Thermal diffusivity of polypyrrole film is larger than that for common nonelectrical conductive polymers. Temperature profile of thermal diffusivity for as‐grown polypyrrole films shows that thermal diffusivity increases with increasing temperature (first running profile), whereas remeasured temperature profile of thermal diffusivity (second or third running profiles) shows the decrease of thermal diffusivity with increasing temperature. Electrical conductivity monotonically increases until the significant decrease of it occurs at the temperature above 130°C. Investigation of these temperature profiles of thermal diffusivity and electrical conductivity has been made by corresponding to thermal analysis data. © 1994 John Wiley & Sons, Inc.
The transport properties of polyimide isomers containing hexafluoroisopropylidene in the diamine residue
Authors: Coleman M. R. , Koros W. J.
Published: April 2003

The effect of modification of the central moiety of the dianhydride residue and isomerism on the gas transport and physical properties were compared for six polyimides containing the hexafluoroisopropylidene group in the diamine residue. Substitution of bulkier groups within the dianhydride residue resulted in disruption of chain packing and slight increases in resistance to chain motions which led to an increase in permeability with little loss in selectivity. The permeabilities and diffusivities in the meta connected polyimide isomers were considerably lower than in the para connected polyimide isomers. Similarly, the permselectivities in the meta connected isomers were consistently higher than in the para connected isomers. These lower permeabilities and higher permselectivities were a result of the more dense packing and a significant suppression of small scale motions in the meta connected isomers. The suppression of segmental mobility in the meta connected isomers was indicated by an increase in the sub Tg transition temperatures in these materials relative to the para connected isomers. The differences in transport properties for these polyimides were attributed to contributions by several factors, including: (1) total free volume (2) distribution of free volume (3) intersegmental resistance to chain motions, and (4) intrasegmental resistance to chain motions. © 1994 John Wiley & Sons, Inc.
Properties of polystyrene‐poly(methylmethacrylate) random and diblock copolymers in dilute and semidilute solutions
Authors: Kent Michael S. , Tirrell Matthew , Lodge Timothy P.
Published: April 2003

Solution properties for random and diblock copolymers of polystyrene (PS) and poly(methyl methacrylate) (PMMA) have been measured by dynamic and total intensity light scattering in solvents of differing quality. The results are compared with the corresponding properties for PS and PMMA homopolymers of similar molecular weight, in order to determine if interactions between unlike monomers are significant. The hydrodynamic radius (Rh) and diffusion second virial coefficient (kd) for the random copolymer are found to be larger than the corresponding values for the homopolymers in a solvent which is near‐theta for the two homopolymers, whereas no such effect is observed for the block copolymer. This suggests that most intrachain interactions occur a relatively short distance along the chain backbone. In a mutual good solvent Rh and kd of the random copolymer are comparable to the average of the values for the homopolymers, indicating that in a good solvent monomer/solvent interactions dominate over monomer/monomer interactions. For an isolated diblock copolymer in a mutual good solvent, there is no evidence that interactions between unlike monomers lead to additional expansion of the entire molecule, as measured by Rh, nor expansion of the individual blocks as probed by light scattering with one block optically masked. However, at low but finite concentration there is evidence (the coefficients of the binary interaction terms in the viscosity and the mutual diffusion coefficient, and the second and third virial coefficients) that a weak ordering effect may exist in block copolymer solutions, far from the conditions where microphase separation occurs. Finally, measurements of ternary polymer‐polymer‐solvent solutions show no dependence on monomer composition or monomer distribution for the tracer diffusion of probe PS‐PMMA copolymers in a PMMA/toluene matrix. This indicate that the frictional interaction is largely unaffected by interactions between unlike monomers. However, there is evidence that the thermodynamic interaction is more unfavorable between a random copolymer and the homopolymer matrix than between a diblock and the matrix. © 1994 John Wiley & Sons, Inc.
Structural studies of poly(paraphenylene), poly(2,5‐thienylene) and their derivatives by solid‐state NMR of 1H and 13C
Authors: Erdmann K. , Czerwinski W. , Gerstein B. C. , Pruski M.
Published: April 2003

Transient techniques in NMR of 1H and 13C were used to study the chemical and physical structures of solid poly(p‐phenylene) (PPP), poly(2,6‐dimethyl‐p‐phenylene oxide) (PDMPO), poly(p‐phenylene sulfide) (PPS), poly(p‐biphenylene sulfide) (PPBS), poly(p‐phenylene selenide) (PPSe), poly(p‐biphenylene selenide) (PPBSe), poly(2,5‐thienylene) (PT), poly(3‐methyl‐2,5‐thienylene) (PMT), and poly(p‐phenylene‐co‐2,5‐thienlyene) (PPPT) of different monomer ratios. 13C NMR confirmed the expected chemical structure for homopolymers, and indicated a random distribution of monomer units in PPPT. Relative fractions of crystalline and interfacial regions were determined by measurements of 1H magnetic relaxation, 13C CP/MAS NMR, and XRD. © 1994 John Wiley & Sons, Inc.
Carbon tetrachloride‐induced crack healing in polycarbonate
Authors: Wu Terhou , Lee Sanboh
Published: April 2003

Crack healing induced by carbon tetrachloride in polycarbonate has been studied at temperatures in the range of 40–60°C. The carbon tetrachloride treatment reduces the glass transition temperature of polycarbonate. Crack healing is observed because the effective glass transition temperature in polycarbonate is reduced to below the test temperature by the carbon tetrachloride treatment. Two distinctive stages of crack healing are divided based on the recovery of mechanical strength and fractograph. The first stage corresponds to the progressive healing due to the convolution of wetting and self‐diffusion, which has a constant crack closure rate. Immediately following the first stage, the second stage, corresponding to the self‐diffusion of polymer chain, enhances the quality of healing behavior. The transport of carbon tetrachloride in polycarbonate consists of case I (concentration gradient controlled) and case II (relaxation controlled) behaviors. The direction of case II is opposite to that of case I. The solubility decreases with increasing temperature, but diffusivity and velocity for mass transfer, crack closure rate, and diffusion coefficient for the diffusion front have the opposite trend. The first stage of crack healing is controlled by case II transport. The transport of carbon tetrachloride changes the fracture behavior of polycarbonate from ductile to brittle. A comparison of crack healing in polycarbonate and poly (methyl methacrylate) is made. © 1994 John Wiley & Sons, Inc.
Electrical conduction in a nonconjugated polymer doped with SnCl4 and SbCl5
Authors: Yu Guo‐Qing , Thakur M.
Published: April 2003

The electrical and optical properties of 1,4‐cis‐polyisoprene before and after doping with SnCl4 and SbCl5 were investigated. The material becomes reddish brown and black upon doping with SnCl4 and SbCl5, respectively, and the conductivity increases by about 11 orders of magnitude. The optical absorption, infrared spectra, elemental analyses, and the studies of reversibility upon compensation indicate that radical cation formation is the most likely mechanism for electrical conduction in these complexes. The results are consistent with previously published articles involving iodine doping. © 1994 © John Wiley & Sons, Inc.
Characterizing domain mixing effects in hydrogen bond‐compatibilized polymer blends
Authors: Taylor‐Smith Ralph E. , Register Richard A.
Published: April 2003

The nature and extent of phase mixing in blends of hydroxyl‐functionalized polystyrene and poly(ethyl acrylate) (PS/PEA), where the driving force for mixing is hydrogen bonding, are characterized by several techniques. Small‐angle x‐ray scattering (SAXS) shows a reduction in average domain size with increasing functionalization level, a result also evident from scanning electron microscopy (SEM). Together, the two techniques reveal a very broad distribution of domain sizes. At high functionalization levels, both SAXS and SEM indicate a high degree of “in‐domain” mixing, with little or no pure PS or PEA remaining in the blends. Mathematical modeling of dynamic mechanical thermal analysis (DMTA) data is employed to quantify this progression. Initially, mixing is primarily interfacial, but as the functionalization level increases, the mixed interphase rapidly grows to occupy the entire material. In agreement with the SAXS and SEM results, DMTA modeling shows that further increases in the functionalization level suppress the amplitude of composition variations in the sample. The onset of extensive in‐domain mixing coincides with the marked changes in stress‐strain behavior observed previously in these materials. © 1994 John Wiley & Sons, Inc.
Temperature effect on solvent diffusion in rigid and semirigid polyimide films
Authors: Chang Ying‐Lun , Jou Jow‐Huei
Published: April 2003

The diffusion of NMP (n‐methyl‐pyrrolidinone) solvent in a semirigid rod‐like PMDA‐ODA (pyromellitic dianhydride‐4,4′‐oxydianiline) film coated on silicon is found to be case I diffusion at temperatures ranging from 30 to 90°C by the use of a bending beam technique. The diffusion constant increases for the 7.4 μm PMDA‐ODA film (which was cured at 300°C) from 3.3 to 318 × 10−11 cm2/s as the diffusion temperature increases from 30 to 90°C. The corresponding hygroscopic stress in the direction parallel to the film decreases with the increase of temperature, possibly due to the softening of the film at elevated temperatures. The diffusion mechanism, however, changes from case II to case I in a rigid rod‐like PMDA‐PDA (pyromellitic dianhydride‐p‐phenylenediamine) film when the diffusion temperature increases. The change in the diffusion mechanism occurs at a higher temperature for thinner films, presumably due to higher ordering and/or orientation in the films. The activation energy for NMP diffusion in the PMDA‐ODA films markedly decreases from 93 to 59 kJ/mole as the film thickness increases from 2.2 μm to 11.3 μm. This may also be attributed to decreased ordering in thicker films. © 1994 John Wiley & Sons, Inc.
Correlation between the fractal dimension of fracture surfaces and fracture toughness for ductile polymer materials
Authors: Lyu Suping , Zhu Xiaoguang , Qi Zongneng
Published: April 2003

A microcrack‐shear band chain model for the fracture of ductile materials is proposed. The fractal dimension (D) of the fracture surfaces is derived and correlated with the fracture toughness (KIc) of ductile materials. The fractal dimension of the fracture surface is predicted to have an inverse trend with the fracture toughness. The theoretical results are consistent with the experimental results of some polymers and metals. © 1994 John Wiley & Sons, Inc.
Effect of cross‐link density on the morphology, thermal and mechanical properties of flexible molded polyurea/urethane foams and films
Authors: Thomas Oomman , Priester, Jr. Ralph D. , Hinze Ken J. , Latham Dwight D.
Published: April 2003

The effect of cross‐link density on the morphology and properties of two flexible molded foam samples was studied. Film samples based on the same foam formulations were also fabricated to study the feasibility of using them for the characterization of complex foam products. Fourier transform infrared spectroscopy (FTIR) and small angle X‐ray scattering (SAXS) data show that films and foam samples have entirely different hard domain ordering. The results of the study of morphology indicate that an increase in cross‐link density appears to increases phase mixing in film and foam samples. Differential scanning calorimetry (DSC) studies indicate that the soft segment glass transition temperature (Tg) is independent of cross‐link density (at levels studied). But for both film and foam samples, morphology clearly dicates the manner in which moisture interacts with the hard domains. Results of the stress‐strain behavior indicate that an increase in cross‐link density increases the modulus and decreases the elongation at break. Mooney‐Rivilin modeling of the stress‐elongation behavior of film shows that the higher cross‐link density sample gives more nonaffine behavior, possibly due to a heterogeneous distribution of hard domains. Similar modeling of the foams was not possible because of their linear stress response to surprisingly high elongation. The results of the power law modeling of stress relaxation response indicates that with an increase in cross‐link density (covalent and virtual), the power law exponent decreases as expected. At levels of cross‐linking and hard segment content studied, stroke‐controlled equilibrium hysteresis was independent of cross‐link density. Normalized dynamic mechanical spectra (DMS) show that the film samples have higher rubbery plateau modulus. The magnitude of the area under the tan δ curve at Tg indicates greater flexibility of polymer segments in foam sample. Structure‐property relationships of cellular materials can be established by characterizing film samples because a parallel trend exists between each group. © 1994 John Wiley & Sons, Inc.
Partial carbonization of aramid fibers
Authors: Zhang Quichen , Liang Ying , Warner Steven B.
Published: April 2003

Heat treatment of aramid fiber was conducted in the temperature range 300–710°C nominally for 10 and 30 s in both static air and flowing nitrogen atmosphere. Crystallinity, crystal orientation, and crystallite size were determined using x‐ray diffraction. Fibers with a skin–core structure were produced at intermediate temperatures, as revealed by scanning electron microscopy of fibers after partial dissolution of the fiber in 95–98% sulfuric acid. The skin, which forms in both nitrogen and air, is amorphous and brittle. It is insoluble in sulfuric acid, suggesting it is a cross‐linked polymer. Formation of the skin may be facilitated by the removal of an aggressive chemical species that forms during heat treatment. The species may diffuse out of the outer layer of the fiber, allowing it to cross‐link. The molecular weight of the dissolved core, analyzed using intrinsic viscosity, decreases with increasing heat treatment temperature. The tenacity, modulus, elongation‐to‐break, and toughness of fibers with a skin–core structure decrease with heat treatment and the fiber loses its fibrillar character. Mechanical property reductions are greater in air than nitrogen. X‐ray data are also consistent with the notion that oxygen assists attack of crystals at high temperatures. Scanning electron microscopy shows that fibers have become skin–core composites with quite different mechanical properties between the two regions. A fiber failure mechanism is proposed. © 1994 John Wiley & Sons, Inc.
Polymer solid electrolytes from the PEG‐PMMA‐LiCF3SO3 system
Authors: Such K. , Stevens J. R. , Wieczorek W. , Siekierski M. , Florjanczyk Z.
Published: April 2003

Highly conductive solid polymeric electrolytes based upon low molecular weight poly(ethylene glycol) and ethylene oxide/propylene oxide copolymers blended with up to 50% by volume of poly(methyl methacrylate) have been synthesized using LiCF3SO3 (25:1 ether oxygen to cation ratio). Room‐temperature ionic conductivities were measured to be in the range 10−4 to 10−5 S/cm for poly(methyl methacrylate) concentrations up to 30% by volume. In some cases, the addition of the poly(methyl methacrylate) enhanced the conductivity. All of the electrolytes studied were either amorphous or crystallized below 0°C. The variation of conductivity with temperature and polymer composition was measured and the results were analyzed in terms of effective medium theory and semiempirical considerations. Ionic transport is coupled to the structural relaxation of the polymer segments. At lower temperatures activated processes were required. Both charge carrier mobility and charge concentration were found to contribute to conduction. The effective medium theory quantitatively describes conductivities of amorphous heterogenous systems of limited miscibility (microphase separation) quite well. For miscible or partially crystalline systems other effects not incorporated in this theory play an important role, and conductivities are measured to be higher than theoretically predicted. © 1994 John Wiley & Sons, Inc.
Some theoretical considerations on diffusion‐controlled one‐chain polymerization in two‐dimensional systems
Authors: Raudino Antonio
Published: April 2003

A simple model has been developed to investigate the differences between 2D and 3D diffusion‐controlled polymerization kinetics. Besides the different analytical structure of 2D and 3D diffusion equation, the model takes into account the dynamics of the polymer chemically reacting end and the restricted motion of the diffusing monomers in a growing polymer network. These effects are strongly related to the dimensionality of the system and may contribute to modulate the polymerization rate. Theoretical considerations suggest different behavior when 2D polymerization takes place in a poor solvent, whereas minor differences should be present in good solvents and 3D systems. © 1994 John Wiley & Sons, Inc.
Lamellar thickness of crystallizable ethene runs in ethene‐propene copolymers by solid state NMR
Authors: Clayden Nigel J.
Published: April 2003

Crystallizable runs of ethene in ethene‐propene copolymers can be identified in 13C CPMAS NMR spectra as a resonance at 33 ppm. In the absence of spin diffusion, the variation in intensity of this resonance with a 1H spin lock will reflect the intrinsic TH1ρ. Spin diffusion leads to a more complex relaxation decay, which reflects the local polymer morphology. Simulations of the spin diffusion process have been carried out for a simplified two‐phase model for the morphology with the aim of determining whether the lamellar thickness of the crystalline and amorphous regions can be found from the TH1ρ observed via the 13C NMR spectrum. Calculations covering the expected range of the input parameters, namely the spin diffusion coefficients, domain lengths, and intrinsic relaxation times, show that, providing the intrinsic relaxation time in the amorphous phase is known, an accurate estimate of the crystalline and amorphous lamellar thicknesses can be made. Analysis of simulated TH1ρ decays indicate that, in general, the time constant of the fastest decaying component can be identified with the intrinsic relaxation time of the amorphous phase. © 1994 John Wiley & Sons, Inc.
Sorption and transport of water vapor in alginic acid, sodium alginate, and alginate‐cobalt complex films
Authors: Hirai Asako , Odani Hisashi
Published: April 2003

The sorption and the transport of water vapor in films of alginic acid (G1), sodium alginate (G1Na), and alginate‐cobalt complex (G1Co) were studied at 30°C by employing the weighing method. Sorption isotherms for all films of G1, G1Na, G1Co were of type II in the Brunauer's classification. The integral absorption from, and desorption to, zero pressure were non‐Fickian type for all films studied. The mean permeability coefficient P, which was determined by the cup method, increased with the increase of vapor pressure, especially in the low vapor pressure region. P for G1Na was much higher than that for G1, which mainly reflects more hygroscopic nature of G1Na than that of G1. The values of P for G1Co were lower than those for G1 at lower pressures and then approached those for G1 at higher vapor pressures. Integral diffusion coefficient D evaluated as P/S, where the solubility coefficient S was evaluated from sorption isotherms, increased rapidly with increasing water concentration and then leveled off. In the concentration region studied, the magnitude of D and its dependence on concentration for H2O‐G1Na system did not differ much from those for H2O‐G1 system. D for H2O‐G1Co system was much lower than that for H2O‐G1 system. © 1994 John Wiley & Sons, Inc.
Effect of side‐chain length on charge mobilities in neutral poly(3‐alkylthiophene)s: Determination from dielectric measurement
Authors: Chen Show‐An , Liao Chien‐Shiun
Published: April 2003

For neutral poly(3‐alkylthiophene)s (P3ATs), the electric modulus formalism of dielectric relaxation measurement together with the use of nonexponential decay function can be applied to describe the behavior of conductivity relaxation and carrier transport. The charge mobilities of neutral P3ATs calculated from conductivity relaxation with the use of the defect‐diffusion model are in agreement with the data from field‐effect transistor measurement. The temperature dependence of charge mobility exhibits a local maximum right after the end of glass transition region, which can be attributed to the transition of soft conformons in the disordered phase to localized conformons. The charge mobilities and activation energies of mobilities for P3ATs are dependent on conjugation length and volume fraction of conducting units. © 1994 John Wiley & Sons, Inc.
A detailed study of sorption equilibria and kinetics of a model disperse dye in cellulose acetate
Authors: Papadokostaki K. G. , Petropoulos J. H.
Published: April 2003

A detailed investigation of the sorption of 4‐aminoazobenzene by cellulose acetate films from aqueous solution is reported. Sorption isotherms at 75 and 60°C were linear up to saturation, in agreement with previous findings that have led to the conclusion that cellulose acetate‐disperse dye systems are thermodynamically ideal. Thermodynamic analysis of these data also gave results consistent with such previous findings. The isotherms for 45 and 25°C, on the other hand, exhibited increasing curvature, in line with similar recent findings for a variety of hydrophobic polymer‐disperse dye systems, and consistent with the presence of some strong absorption sites. However, the situation appears to be more complex than envisaged by simple dual‐mode sorption theory. Early time desorption kinetic data were found to be consistent with Fick's law, with no indication of any significant dependence of the diffusion coefficient D on concentration (in the medium‐ to high‐concentration range) or on film thickness. On the other hand, D was affected significantly by the history of film formation, the method of introducing the dye or heat treatment of the film. The origin of these effects was traced by DSC to definite microstructural differences. Late time kinetic data deviated significantly from the theoretical predictions based on the corresponding early time data, indicating a progressive slowdown of the desorption process. The deviations in question were generally more marked at higher temperature or film thickness, or when dyeing had been effected from the vapor phase, and were attributed to slow release of strongly adsorbed dye molecules. © 1994 John Wiley & Sons, Inc.
The growth and interaction of conjugated polymer chains, the unpaired electron localization
Authors: Gordon Delyara A. , Mikhailov Alfa I.
Published: April 2003

An ESR method was used to study the structure of the macroradical of the propagating chain Rp in the low‐temperature, solid‐phase polymerization of p‐diethynylbenzene (DEB). The ESR spectra for γ‐irradiated DEB samples and those of DEB deuterated in the ethynyl group showed that in the range 77–230 K, the unpaired electron of the macroradical was localized on one of the monomer links. At 230–310 K, its delocalization in a polyconjugated system took place because of addition of a linear macroradical to a double bond of a polymer molecule. The encounter of the macroradical with double bond probably occurs as polymer chain propagation. © 1994 John Wiley & Sons, Inc.
ATR analysis of the oil‐absorption ability of a two‐part epoxy adhesive on oil‐contaminated metal substrates
Authors: Hong S. G. , Shu H. X.
Published: April 2003

The oil absorption of a room‐temperature‐cured, two‐part epoxy adhesive on three metal substrates, cold‐rolled steel (CRS), 2024‐aluminum, and electrogalvanized steel (EGS), was studied using attenuated total reflection infrared spectroscopy (ATR). From relative absorbance ratios calculated from ATR spectra taken at different penetration depths, it was determined that the effectiveness of the adhesive in replacing the oil from the metal surfaces followed in the order of 2024‐Al > CRS > EGS. As thick as 20 microns oil could be absorbed from the 2024‐Al and CRS surfaces, but much less oil could be absorbed from the oiled EGS substrate. However, the heat applied during cure could greatly help the adhesive absorb oil from the EGS substrate. Distributions of adhesive functional groups with respect to penetration depths were found in adhesive layers adjacent to metal surfaces. The abundance of curing agents in the adhesive/EGS interfacial region resulted in the incomplete oil absorption observed on the oiled EGS substrate. The results from ATR also showed that the oil did not inhibit the cure of the adhesive in the bulk. © 1994 John Wiley & Sons, Inc.
In situ X‐ray scattering studies of lyotropic liquid crystalline PBO and PBZT monofilament drawing
Authors: Radler M. J. , Landes B. G. , Nolan S. J. , Broomall C. F. , Chritz T. C. , Rudolf P. R. , Mills M. E. , Bubeck R. A.
Published: April 2003

The results of a series of novel synchrontron‐based in situ x‐ray scattering experiments of monofilament fiber drawing from lyotropic solutions of poly(cis‐benzoxazole) (PBO) and poly(trans‐benzothiazole) (PBZT) are reported. The purpose of the study is to determine orientation and microstructure development in the draw zone as a function of shear rate in the capillary die, and spin draw ratio (SDR). The transition of the extrudate from opaque to the transparent is complete at about a SDR = 3 and f of 0.9. The filament orientation parameter (f) was found to depend strongly on spin draw ratio, but not shear rate. The orientation was found to increase down the extrudate toward completion of the draw down as one proceeds further from the die face up to an extrudate length of 3.8 cm. Coherence lengths on the order of 19 nm (axial), and 4.5 nm (lateral) have been observed. These “microdomain” sizes are consistent with the “crystallite” sizes typically observed in coagulated fiber. The occurrence of these microdomains in the draw zone as a precursor to the microfibrillar structure is believed to be the origin of low filament compressive strength. © 1994 John Wiley & Sons, Inc.
Axial X‐ray scattering on high‐performance polymeric fibers
Authors: Bai S. J.
Published: April 2003

High‐temperature polymers were spum from liquid‐crystalline solutions into fibers of superior thermal stability and mechanical properties. Fibers of two extended‐chain polymers poly(p‐phenyleneterephthalamide), PPTA, and poly‐2,5‐benzoxazole, ABPBO, as well as a rod‐like polymer poly(p‐phenylenebenzobisoxazole), PBO, were examined by axial x‐ray scattering. Both wide‐angle scattering and small‐angle scattering were performed with CuKα radiation aiming along the fiber axis (c‐axis) for structural information on the a‐b lattice plane. In addition to previously reported lattice structure, the PPTA fibers (Kevlar® 29, 49, and 149) showed strong [004] and a [022] reflections suggesting that segments of the PPTA molecules were transverse to the fiber axis. This unique fiber structure is more prominent and the void content is less for the PPTA fibers with higher tensile modulus, (i.e., Kevlar® 149 > Kevlar® 49 > Kevlar® 29). Similar measurements on thermally annealed ABPBO and PBO fibers showed no [00l], [h0l], or [0kl] reflection indicative of a truly uniaxial molecular orientation. Evidence of microfibrillar order was discovered for the Kevlar® fibers and the ABPBO fiber. Results of conventional x‐ray scattering on these fibers were compared and reconciled. © 1994 John Wiley & Sons, Inc.
Free volume, hole theory and thermal properties
Authors: Simha Robert , Carri Gustavo
Published: April 2003

Free volume ideas have been employed extensively in the interpretation of equilibrium processes and as a measure of molecular mobility. More recently, the vacancy fraction h, defined in our hole theory, has served to provide a link between diverse processes. This raises a question regarding the relation between the van der Waals type of free volume and h. As an important and useful result, valid for polymers and low molar mass fluids, simple relations are obtained between the van der Waals volume Vw, computed according to Bondi's structural rules, and the scaling volume V* in the hole theory. This is defined by the intersegmental potential and extracted from the equation of state. In turn, this result enables us to compute the corresponding scaling temperature T*. In this manner the theory predicts the volume‐temperature function for a melt, based on a single experimental datum. Corresponding considerations are presented for the glassy state. The quantitative relation between the van der Waals type of free volume vf and h derived makes it possible to reconsider various empirical correlations involving the former. © 1994 John Wiley & Sons, Inc.
The morphology of gel‐spun polyethylene fibers, investigated by solid‐state 13C NMR
Authors: Chen Wei , Fu Yigang , Wunderlich Bernhard , Cheng Jinlong
Published: April 2003

Gel‐spun polyethylene fibers were analyzed at room temperature with 13C NMR, using both, CP‐MAS and BILEV (Bloch‐decay with two‐level decoupling). The analysis shows the existence of three different components in the fiber sample—a crystal component, an amorphous component and a third component, named the oriented, mobile component. This latter component has a 13 C chemical shift that is similar to the crystalline chemical shift, but with a mobility, expressed by T1, that is closer to the amorphous component. The chemical shift and T1 are as follows: 34.06 ppm and 28.1 s for the crystalline part; 31.70 ppm and 0.3 s for the amorphous part; and 34.06 ppm and 1.8 s for the oriented mobile component. The percentages are 63.2% crystalline; 34.0% oriented mobile, 2.8% amorphous component. Using proton spin‐diffusion measurements, it was possible to estimate the domain size of the crystalline and oriented mobile components to be 62.8 and 13.2 nm, respectively, in agreement with the results of a full‐pattern x‐ray study on the same sample. After melting of the fiber at 450 K and recrystallinzation on cooling, the oriented, mobile component is dramatically reduced. © 1994 John Wiley & Sons, Inc.
Fluorescence nonradiative energy transfer in bulk polymer and miscible and phase‐separated polymer blends: A quantitative analysis including correlation effects
Authors: Mendelsohn Alice S. , Torkelson John M. , de la Cruz Monica Olvera
Published: April 2003

A theoretical analysis has been developed to predict fluorescence nonradiative energy transfer (NBET) behavior in homogeneous and phase‐separated polymer blends. Conditions where intermolecular correlations need to be included are examined by first investigating the effect of including intermolecular correlations in predictions of NRET behavior in donor and trap (acceptor) end‐labeled polymer melts. Donor fluorescence decays and energy transfer efficiencies are predicted for several different polymer systems using donor‐trap intermolecular correlations in the theoretical analysis. These results are compared quantitatively to the same predictions recalculated without correlations and demonstrate the need to consider the effects of correlations when analyzing NRET measurements used for quantitative study of phase behavior. For the nonradiative energy transfer systems investigated here, correlation effects can often result in substantial differences, up to 60% as compared to the uncorrelated case, in predictions of relative energy transfer efficiency for bulk polymer. In the case of the blends, the effect of including intermolecular correlations is strongly a function of composition. A two‐phase model is proposed to establish a quantitative method for relating energy transfer efficiency to phase‐separated blend composition, and it is demonstrated that significant errors in interpretation of experimental NRET data may result if correlation effects are not included. © 1994 John Wiley & Sons, Inc.
Phase behavior in mixtures of a homopolymer and a block copolymer 1. FTIR and DSC studies
Authors: Xie Rui , Yang Bingxing , Jiang Bingzheng
Published: April 2003

Miscibility in blends of three styrene‐butadiene‐styrene and one styrene‐isoprene‐styrene triblock copolymers containing 28%, 30%, 48%, and 14% by weight of polystyrene, respectively, with poly(vinyl methyl ether) (PVME) were investigated by FTIR spectroscopy and differential scanning calorimetry (DSC). It was found from the optical clarity and the glass transition temperature behavior that the blends show miscibility for each kind of triblock copolymers below a certain concentration of PVME. The concentration range to show miscibility becomes wider as the polystyrene content and molecular weight of PS segment in the triblock copolymers increase. From the FTIR results, the relative peak intensity of the 1100 cm‐1 region due to COCH3 band of PVME and peak position of 698 cm‐1 region due to phenyl ring are sensitive to the miscibility of SBS(SIS)/PVME blends. The results show that the miscibility in SBS(SIS)/PVME blends is greatly affected by the composition of the copolymers and the polystyrene content in the triblock copolymers. Molecular weights of polystyrene segments have also affected the miscibility of the blends. ©1995 John Wiley & Sons, Inc.
Measurement of thermal diffusivity and specific heat capacity of polymers by laser flash method
Authors: Agari Y. , Ueda A. , Nagai S.
Published: April 2003

We measured thermal diffusivity and heat capacity of polymers by laser flash method, and the effects of measurement condition and sample size on the accuracy of the measurement are discussed. Thermal diffusivities of PTFE films with thickness 200–500 μm were the same as those data that have been reported. But, the data for film thickness less than 200 μm have to be corrected by an equation to cancel thermal resistance between sample film and graphite layers for receiving light and detecting temperature. Thermal diffusivity was almost unaffected by the size of area vertical to the direction of laser pulse, because heat flow for the direction could be negligible. Specific heat capacity of polymer film was exactly measured at room temperature, provided that low absorbed energy (< 0.3 J) and enough sample mass (> 25 mg) were satisfied as measuring conditions. Thermal diffusivity curve of PS or PC versus temperature had a terrace around Tg, whereas that of PE decreased monotonously with increasing in temperature until Tm. Further, we estimated relative specific heat capacity (RCp) by calculating ratios of heat capacities at various temperatures to the one at 299 K. RCp for PS obtained by laser flash method was larger than that obtained by DSC method, whereas the RCps for PE obtained by the both methods agreed with one another until Tm (305 K). RCp for PS decreased linearly, with increase in temperature after it increased linearly until Tg (389 K), showing similarity to temperature dependency of thermal conductivity. RCp for PE also decreased until Tm, similar to thermal conductivity. ©1995 John Wiley & Sons, Inc.
Aggregation of sulfonated poly(p‐phenylene terephthalamide) in dilute solutions
Authors: Chu Evan Y. , Xu Z. S. , Lee C. M. , Sek Cindy K. F. , Okamoto Y. , Pearce E. M. , Kwei T. K.
Published: April 2003

The viscosities of dilute solutions of poly(p‐phenylene terephthalamide), PPTS, in dimethylacetamide, water, and their mixtures were determined. The reduced viscosity plot in dimethylacetamide shows a negative slope. When the water content in the mixed solvent in 90% or higher, there is an upswing in the reduced viscosity values at concentrations below 0.1 g/dL. The latter behavior suggests a “polyelectrolyte” effect. However, an association model was found to be able to explain the viscosity behaviors in both solvents. ©1995 John Wiley & Sons, Inc.