bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of the addition of amine diluents on the physical properties of poly(methyl methacrylate‐co‐methacrylic acid) copolymers obtained by partial hydrolysis of PMMA
Authors: Smith P. , Goulet L. 
Published: April 2003

AbstractAtactic poly(methyl methacrylate) was partially hydrolyzed in concentrated sulfuric acid to obtain methacrylic acid contents (MAA) of 3–12 mol %. The resulting copolymers were characterized by differential scanning calorimetry, Fourier transform infrared spectroscopy (FTIR), and gel permeation chromatography. The dynamic mechanical properties of these copolymers were studied in the glass transition region at a frequency of 1 Hz following neutralization with various low‐molecular weight linear (e.g., octylamine) and rigid (e.g., 1‐adamantanamine, ADA) primary amines. While the addition of linear amines to the copolymers was found to depress Tg, the addition of ADA had relatively little effect. FTIR spectra of all these blends indicated that proton transfer occurred from the MAA units to the amines, resulting in H‐bonded ion pairs which behaved mechanically as grafts. Itwas concluded that the ion pairs resulting from protonation of the ADA units by MAA are less effective at reducing free volume than similar ones resulting from the reaction of a sulfonic acid with ADA. © 1993 John Wiley & Sons, Inc.
Study of orientational order in a nematic polysiloxane by utilizing the “guest–host” effect
Authors: Wolarz Eryk , Bauman Danuta 
Published: April 2003

AbstractA nematogenic side‐chain polysiloxane is investigated by means of absorption and fluo‐rescence spectroscopy.4‐Dimethylamino‐4′‐nitrostilbene (DANS) is dissolved in the poly‐meric matrix as a guest probe. The orientational order and the molecular distribution function have been determined from measurements of polarized absorption and fluorescence spectra. It has been found that fluorescence spectroscopy affords a method for determination of the phase transition temperatures of liquid–crystalline polymers. © 1993 John Wiley & Sons, Inc.
Modeling strategy for systems with both stepwise and chainwise chemistry revisited. The directionality effect on the build‐up of the network structure
Authors: Riccardi Carmen C. , Williams Roberto J. J. 
Published: April 2003

AbstractA comparison of rigorous and approximate models for the build‐up of epoxy‐amine networks with simultaneous etherification is presented. Contrary to a recent publication, it is shown that naïve statistical models perform very well in predicting statistical parameters when the different directions of network growth are distinguished in the statement of the recursive procedure. Slightly lower values of gel conversions are predicted by the approximate model, a fact that is consistent with the wider distribution of chain lengths resulting from the random recombination procedure. © 1993 John Wiley & Sons, Inc.
On catenate network formation by end‐linking reactions
Authors: Iwata Kazuyoshi , Ohtsuki Toshiya 
Published: April 2003

AbstractCatenate network formation by end‐linking reactions of linear chains with bifunctional regents is studied theoretically and by computer simulations. It is found that the reaction cannot reach its stationary limit, and catenate networks are never formed by this method. An alternative method that will lead to catenate networks nearly in the topological equilibrium state is proposed. It is pointed out that catenate networks are an ideal system for studying the role of entanglement in rubber elasticity. © 1993 John Wiley & Sons, Inc.
A dual‐mode interpretation of nuclear spin relaxation for 13CO2 sorbed in polystyrene
Authors: Bandis A. , Cauley B. J. , Inglefield C. E. , Wen W.‐Y. , Inglefield P. T. , Jones A. A. , Melc'Uk A. 
Published: April 2003

AbstractRecently we presented a dual‐mode interpretation of the nuclear spin relaxation for 13CO2 sorbed in polycarbonate [E. J. Cain, W.‐Y. Wen, A. A. Jones, P. T. Inglefield, B. J. Cauley, and J. T. Bendler, Journal of Polymer Science, Part B, Polymer Physics, Vol. 29, p. 1009 (1991)]. We have made similar investigation on spin relaxation for 13CO2 sorbed in polystyrene and are presenting the results in this report. 13C spin‐lattice relaxation, spin‐spin relaxation, and nuclear Overhauser enhancements (NOE) are reported for 13CO2 sorbed in glassy polystyrene. These spin relaxation parameters were determined as a function of temperature and Larmor frequency. A quantitative interpretation is based on a two‐site, rapid exchange model, which is consistent with the NMR result. Gas molecules in the dissolved site have rotational, collisional, and translational dynamics typical of low molecular weight liquids. Sorbed molecules in the Langmuir site have much slower rotational and translational motions. The activation energy for motions in the dissolved site is about 7.5 KJ/mol, while that for the Langmuir site is about 15.5 KJ/mol. The translational diffusion constants derived from the NMR data range from 10−7 to 10−9 cm2/s and are consistent with the apparent diffusion constant from the permeability measurements of 4.9 × 10−8cm2/s at 35°C. A relation between the permeability value and the NMR values is available from a theoretical description of the dual‐mode model in terms of a random walk on a lattice containing two sites. As a modification of our previous lattice model (E. J. Cain et al., Journal of Polymer Science, Part B, Polymer Physics, Vol. 29, p. 1009 (1991)), the temperature dependence of the fraction of Langmuir sites in the lattice is taken into account. Parameter values characterizing the motion of CO2 in polystyrene are found to be similar to the corresponding ones in polycarbonate. © 1993 John Wiley & Sons, Inc.
The response of microstructure to processing in a series of poly(siloxaneimide) copolymers
Authors: Samseth Jon , Spontak Richard J. , Mortensen Kell 
Published: April 2003

AbstractPoly(siloxaneimide) (PSI) segmented copolymers exhibit organized microdomains if the blocks are sufficiently incompatible. As with neat diblock and triblock copolymers, the processing route employed to prepare films of PSI materials is expected to influence the dimensions and/or morphology of the resultant microstructure. In this work, small‐angle neutron scattering (SANS) is utilized to characterize the disordered microstructure found in films of a series of PSI copolymers which are subjected to solvent casting and various thermal treatments. Microstructural dimensions such as the periodicity and correlation length are deduced from the Teubner‐Strey (TS) model for disordered microemulsions. The scattering intensity of each copolymer up to q = 5.0 nm−1, where q is the scattering vector, is found to scale as q−2.8+−0.1. Results indicate that processing the materials as cast films or as melt‐pressed films allowed to cool slowly has a small, but discernible, effect on microstructural characteristics. SANS profiles of films quenched from elevated temperatures reveal a clear transition in microdomain periodicity, which correlates well with the glass transition temperature of the imide microphase in these and other materials of similar chemical structure. © 1993 John Wiley & Sons, Inc.
Structure and properties of semicrystalline polymers via high‐frequency acoustic and x‐ray measurements. I. Ferroelectric P(VDF/TrFE) copolymer
Authors: Krüger J. K. , Prechtl M. , Wittmann J. C. , Meyer S. , Legrand J. F. , D'Asseza G. 
Published: April 2003

AbstractAcoustic, opto‐acoustic, and x‐ray investigations have been performed in order to study the influence of irradiation, electrical poling, and mechanical orientation on the morphology of ferroelectric random copolymers of vinylidene fluoride and trifluorethylene {P[VDF/TrFE] (70/30)}. The influences of these different treatments on the molecular orientation distribution of the amorphous and crystalline phases are discussed, as well as their influences on the crystallinity of the material. The elastic stiffness and the related viscosity tensors of P[VDF/TrFE] (70/30), the elastic stiffness modulus of the amorphous matrix, and the hierarchy of stiffness constants of the crystalline state have been determined. © 1993 John Wiley & Sons, Inc.
Segmental orientation in aromatic polyesters by solid‐state nuclear magnetic resonance and modeling
Authors: Rutledge G. C. , Ward I. M. 
Published: April 2003

AbstractProton spin‐spin relaxation measurements and the corresponding second moments 〈ΔH2〉 of broad line spectra are reported for powder samples of homopolyesters of hydroxybenzoic acid (HBA) and hydroxynaphthoic acid (HNA) and for oriented tape samples of HIQ‐35, a terpolyester composed of HBA, isophthalic acid, and hydroquinone. These are reviewed in relation to previous results reported for related copolyesters of HBA and HNA. In particular, the values of 〈ΔH2〉 for isotropic samples were predominantly composition dependent and of little practical value for studies of detailed molecular structure. Orientation‐dependent second‐moment anisotropies, on the other hand, provide indirect insight into molecular conformation and orientation through comparison with results from detailed molecular models. The orientations of monomers are well described by the distribution function proposed by Bower; a quantitatively accurate description of the orientation distribution in cylindrically symmetric geometries requires only the Legendre polynomial coefficient 〈P2〉. Modeling results based on rotational isomeric state theory for chain segments of finite length and high degrees of orientation successfully reproduce the degrees of anisotropy observed in 〈ΔH2〉 for both HBA/HNA and HIQ polymers. The model provides a link between measures of orientation obtained at different molecular scales by mechanical analysis, wide‐angle x‐ray diffraction, and nuclear magnetic resonance spectroscopy. © 1993 John Wiley & Sons, Inc.
Poly(N‐n‐butylitaconimide). Preparation and characterization
Authors: Matsumoto Akikazu , Umehara Sachiyo , Watanabe Hiroyuki , Otsu Takayuki 
Published: April 2003

AbstractPoly(N‐n‐butylitaconimide) was prepared by radical polymerization in benzene and in bulk at 60°C and was subsequently fractionated at 30°C with benzene and methanol as solvent and nonsolvent, respectively. Relationships between molecular weight and intrinsic viscosity (Mark‐Houwink‐Sakurada equations) in tetrahydrofuran, benzene, and toluene at 30°C are established. From the Burchard‐Stockmayer‐Fixman plot, the characteristic ratio of this polymer is determined, and local chain conformation is discussed in relation to the termination process in radical polymerization. © 1993 John Wiley & Sons, Inc.
Gas sorption and diffusion in hydrogen‐bonded polymers. I. Vinyl alcohol/vinyl butyral copolymers
Authors: Reimers M. J. , Cibulsky M. J. , Barbari T. A. 
Published: April 2003

AbstractA series of vinyl alcohol/vinyl butyral copolymers was examined to assess the effect of internal hydrogen bonding on gas sorption and diffusion. Sorption and permeation measurements for carbon dioxide and methane were performed on four vinyl alcohol/vinyl butyral copolymers. Upon comparing the various data, it was found that hydrogen‐bonded copolymers exhibit a much wider variation in diffusion coefficient than non‐hydrogen‐bonded copolymers. The fractional free volumes of the studied copolymers were considerably lower than expected based on values of the diffusion coefficient. This may be due to the fact that predicted occupied volumes are too large and that the effect of internal hydrogen bonding is not accounted for properly. Using a relationship between infrared spectral shift and hydrogen‐bond length, fractional free volumes in the hydrogen bonded copolymers were correlated with the interatomic spacing associated with the hydrogen bond. This implies that the average length of a hydrogen bond can be used as a measure of chain packing in hydrogen‐bonded polymers. © 1993 John Wiley & Sons, Inc.
The effect of N2O4 on the crystalline structure of cellulose
Authors: Gert E. V. , Torgashov V. I. , Shishonok M. V. , Sinyak S. I. , Kaputskii F. N. 
Published: April 2003

AbstractDepending on reaction conditions, the system cellulose–N2O4 may give two different unstable crystalline compounds, one being an ester (cellulose trinitrite), the second, an adduct of cellulose and HNO3 (the Knecht compound). For these compounds, mechanisms of the formation of the crystalline phase as a result of topochemical reaction and self‐organization are discussed. The different characteristics of structural transformations of the fiber under nitrosation and nitration are noted. The existence of polymorphic forms of the Knecht compound is suggested. These labile nitrogen‐containing compounds make possible the regeneration of cellulose in its various modifications (cellulose I, II, IV, or amorphous cellulose) from the cellulose–N2O4 system. The formation of unstable compounds and their ability to crystallize in the reaction medium allows the passage from amorphous cellulose to its crystalline modifications II or IV under mild conditions. The causes of decrystallization of cellulose by N2O4 are established. © 1993 John Wiley & Sons, Inc.
Anomalous freezing point depression of solvents in a swollen homogeneous rubber network
Authors: Grobler J. H. A. , McGill W. J. 
Published: April 2003

AbstractThe freezing point depression of a solvent, imbibed by crosslinked polyisoprene networks, was studied. It is argued that in a swollen vulcanizate, polymer chains subdivide the solvent, creating zones too small for nucleation on cooling to occur at the normal freezing point of the solvent. The freezing point of the solvent is identified with the temperature at which nuclei can form in the swollen network. A linear relationship between freezing point and the volume fraction of rubber in the swollen gel is predicted for a uniformly crosslinked network. Such a relationship is shown to hold for gamma‐irradiated polyisoprene, but not for peroxide‐cured samples, where deviations from linearity are interpreted as indicative of nonuniformity in the network. © 1993 John Wiley & Sons, Inc.
Scattering properties, stability analysis, and phase separation of polyelectrolyte mixtures
Authors: Benmouna M. , Aziz S. , Vilgis T. A. 
Published: April 2003

AbstractThe conditions of stability for weakly charged polyelectrolyte mixtures are analyzed from a scattering theory developed previously. In the thermodynamic limit of zero wave vector q = 0, it is found that electrostatic interaction induces a compatibility enhancement which is discussed for various cases of charge distributions. The condition of microphase separation transition at the wave vector for which the scattering is a maximum is also discussed. © 1993 John Wiley & Sons, Inc.
Correlation between chain segment and ion mobility in an epoxy resin system. A free volume analysis
Authors: Simpson Joycelyn O. , Bidstrup Sue Ann 
Published: April 2003

AbstractSteady shear viscosity and ionic conductivity have been measured for nine commercial diglycidyl ether of bisphenol‐A (DGEBA) epoxy resins with molecular weights ranging from 340 to 14,200. The temperature dependence of viscosity and ionic conductivity was modeled using free volume viscosity and ionic conductivity relationships, which correlate the fractional free volume required for polymer chain segment motion (B) and the fractional free volume required for ion motion (B′) with polymer structure. The fractional free volume required for polymer chain segment mobility was observed to increase systematically with the molecular weight of the resins. The fractional free volume required for ion mobility did not vary for the resin series. A stoichiometric mixture of a low molecular weight DGEBA resin and a 4,4′‐diaminodiphenyl sulfone cross‐linker was partially polymerized to extents of reaction ranging from 0% to 49%. The fractional free volume required for polymer segment mobility for these partially polymerized samples was consistent with results for the neat resins. © 1993 John Wiley & Sons, Inc.
Reactive rubbers as toughening agents for thermoset polyester resins. Molecular analysis by FTIR and fracture behavior of the resulting blends
Authors: Martuscelli E. , Musto P. , Ragosta G. , Scarinzi G. , Bertotti E. 
Published: April 2003

AbstractA reactive rubber obtained by isocyanation of hydroxyl‐terminated polybutadiene was used as toughening agent for an unsaturated polyester resin. Both the isocyanation and the successive reaction between the modified rubber and the polyester were investigated by Fourier‐transform infrared spectroscopy (FTIR). Fracture measurements at high and low strain rate were carried out on the cured materials to test their toughness. The failure mechanisms were established by morphological analysis of fractured surfaces, performed by scanning electron microscopy. © 1993 John Wiley & Sons, Inc.
Haze and extinction for a composite medium with quasitransparent optically stratified particles
Authors: Alexander‐Katz Roberto 
Published: April 2003

AbstractHaze and extinction are studied for coreshell particles in a matrix near transparency. It is shown that, close to transparency, a core‐shell particle behaves optically differently from a nonstructured particle due to the presence of a minimum in the scattering pattern for any particle size. For small particles or domains (<λ/2), this difference is more pronounced. In particular, compositional effects on haze and extinction are studied. It is found that under certain conditions, for the same global composition, strongly optically stratified par‐ticles give lower haze than the homogeneously distributed one by one to two orders of magnitude. The same occurs with the extinction coefficient, however the global composition at which this becomes important differs from that corresponding to a minimum haze. The origin of this difference is discussed in the light of the structure of the scattering pattern in each case. This implies that, for a transparent polymer blend with stratified domains, the minimum haze, maximum transmission and the theoretically perfect matching com‐positions, are all different. Finally, it is shown that, for small highly optically inhomogeneous core‐shell particles, haze goes through an inflection point with increasing particle size, in contrast with the usual monotonically increasing, singly concave, behavior. © 1993 John Wiley & Sons, Inc.
Permeation of high‐pressure gases in poly(ethylene‐co‐vinyl acetate)
Authors: Naito Yasutoshi , Bourbon Dominique , Terada Katsuhiko , Kamiya Yoshinori 
Published: April 2003

AbstractA previously proposed theoretical treatment to elucidate the pressure dependence of gas permeability is improved in order to apply it to polymer‐gas systems in which gas dissolution follows the Flory‐Huggins equation. Permeation rates of N2, CH4, and CO2 in poly(ethylene‐co‐vinyl acetate) are measured in the pressure range below 90 atm at 10–40°C, and the effect of pressure on permeability is found for each gas. The data are analyzed using the improved method to estimate the contributions of concentration and hydrostatic pressure to the pressure dependence of permeability. The concentration effect decreases with increasing temperature, whereas the hydrostatic‐pressure effect is almost independent of temperature. Crystallinity dependence of the concentration effect is discussed in connection with high‐pressure permeation data of other semicrystalline polymers reported elsewhere. © 1993 John Wiley & Sons, Inc.
NMR study of the structure of poly(N‐benzoyl‐8‐octanelactam)
Authors: Kříž Jaroslav , Puffr Rudolf 
Published: April 2003

AbstractThe structure of a polymer prepared by the polymerization of N‐benzoyl‐8‐octanelactam initiated with benzoic acid was studied by 1H and 13C NMR, using S‐INEPT, COSY, COLOC, and ROSEY methods, with the aid of model oligomers. Beside the expected N‐benzoylated segments, the polymer also contained deacylated segments and about 50% of branching units. The polymer can be characterized as a statistical, highly branched copolymer of N‐benzoyl‐8‐octanelactam and 8‐octanelactam. © 1993 John Wiley & Sons, Inc.
Radiation‐induced crosslinking of polyethylene in the presence of acetylene: A gel fraction, UV‐visible, and ESR spectroscopy study
Authors: Jones R. A. , Salmon G. A. , Ward I. M. 
Published: April 2003

AbstractElectron‐spin resonance (ESR) and altraviolet (UV) visible spectroscopic evidence has been found for the formation of diene, triene and tetraene, following the irradiation of polyethylene in the presence of acetylene. The polyenes are formed by a mechanism which is different from that observed under vacuum or with inert gas saturation. The sum of the G (polyene) values obtained by UV spectroscopy is almost half that of initial radical formation. It is concluded that polyene bridges, predominantly diene, form crosslinks between radical pairs. G (X) values determined from gel fraction data, using Saito‐Kang‐Dole theory, are found to be greatly in error and misrepresentative of crosslink changes. © 1993 John Wiley & Sons, Inc.
Electrical, thermal, and photo properties of poly(phenylene vinylene) precursors: I. Laser‐induced elimination reactions in precursor polymer films
Authors: Torres‐Filho Afranio , Lenz Robert W. 
Published: April 2003

AbstractThe elimination reaction of polyelectrolyte films of poly(phenylene vinylene) precursor polymers into the fully conjugated chain was induced by irradiation with an Ar+ laser emitting at 514.5 nm. The experiments were conducted using as cast precursor polyelec‐trolyte films of both the unsubstituted poly(phenylene vinylene), H‐PPV, and its 2,5‐dimethoxyphenylene derivative, DMEO‐PPV. Precursor polymer films impregnated with an azosulfonic dye, which had a strong absorption at the laser emission wavelength, were also irradiated. The elimination reaction was followed by comparing the elemental analysis and the infrared and visibleultraviolet spectra of the irradiated and nonirradiated areas. With the unsubstituted PPV film no elimination was detected even at power fluence levels up to approximately 350 W/cm‐2, but elimination and conversion to the conjugated polymer could be observed at 10 W/cm‐2 when the dye was present. For DMEO‐PPV the elimination reaction occurred with or without dye impregnation, and similar marking threshold values were measured in both cases. The molecular mechanism used to explain such observations and the possible application in the area of microelectronics are also discussed. © 1993 John Wiley & Sons, Inc.
Gas transport properties of poly(2,2,4,4‐tetramethyl cyclobutane carbonate)
Authors: Aguilar‐Vega M. , Paul D. R. 
Published: April 2003

AbstractGas transport properties of semicrystalline films of poly(2,2,4,4‐tetramethyl cyclobutane carbonate) (TMCBPC) were studied. Permeability coefficients for He, O2, N2, CH4, and CO2 at 35°C for pressures between 1 and 20 atm are reported as well as sorption isotherms for N2, CH4, and CO2 at the same conditions. The permeability coefficients for TMCBPC are larger than corresponding values for the aromatic bisphenol‐A polycarbonate (PC) and tetramethyl bisphenol‐A polycarbonate (TMPC), even though the TMCBPC films are semicrystalline. These results are explained on the basis of the larger free volume available for permeation in this polymer. Significant TMCBPC plasticization by CO2 was also observed and this causes typical time‐dependent behavior. The plasticization process starts at very low pressures compared with the behavior of aromatic polycarbonates PC and TMPC. This early onset of plasticization seems to be related also to the larger free volume in the amorphous phase of TMCBPC which favors high gas sorption. The diffusion coefficients for TMCBPC are also larger than those reported for the aromatic polycarbonates PC and TMPC. Ideal gas separation factors were found to follow the usual trend; that is, as permeability increases, the ideal separation factor decreases. © 1993 John Wiley & Sons, Inc.