bluuebunny/crossref_metadata_2025 huggingface dataset:
Volumetric effects in the injection molding of polymers
Authors: Isayev A. I. , Hariharan T.
Published: May 2005

Density and shrinkage measurements have been performed in quenched and molded slabs from polystyrene (PS) and poly (methylmethacrylate) (PMMA). Various processing conditions have been employed and their effect on density and shrinkage variation in the final parts, as well as volumetric aging vs. Elapsed time at room temperature, have been elucidated. A numerical simulation of the density variation in quenched parts and their aging has been performed by using first‐order rate theory for volumetric changes in conjunction with solving the transient one‐dimensional heat‐conduction equation with a convective heat‐transfer boundary condition at surface. A numerical simulation of the shrinkage in molded parts has been carried out by using the equation of state with a simultaneous solving of the governing equations for one‐dimensional mold filling during the cavity filling stage followed by transient one‐dimensional conduction during packing and cooling stages. Predicted results for density and shrinkage are compared with experimental data.
Measurement of thermal conductivity of polymer melts by the line‐source method
Authors: Lobo Hubert , Cohen Claude
Published: May 2005

An apparatus has been developed for the measurement of thermal conductivity of polymer melts. Based on the transient “line source method,” it is ideally suited to these materials because measurements can be made quickly, before the onset of thermal degradation. Also, little or no sample preparation is required. A number of commercial polymers have been tested, including some glass‐fiber filled composites.
Blends of cellulose with nylon 6 and poly(ε‐caprolactone) prepared by a solution‐coagulation method
Authors: Nishio Yoshtyuki , Manley R. St. John
Published: May 2005

Conditions are described for preparing blends of cellulose with nylon 6 (Ny6) and poly(ε‐caprolactone) (PCL) from solutions in N,N‐dimethylacetamide (DMAc)– lithium chloride (LiCl) by coagulation in a non‐solvent. The binary blend films of both series, obtained over a wide composition range (10/90–90/10) from mixed polymer solutions, were characterized by wide‐angle x‐ray diffraction (WAXD), differential scanning calorimetry (DSC), and dynamic mechanical measurements. In the two series of cellulose blends the other component (Ny6 or PCL) was crystalline at every composition, but there was some degree of disproportional reduction of the crystallinity with an increase in cellulose content. From the dynamic Mechanical testing, the cellulose/Ny6 blends were found to be almost immiscible, although the possibility of a certain level of partial miscibility in the non‐crystalline regions was admitted at high cellulose concentrations (>80 wt%). For the cellulose/PCL blends, it was found that there was evidently an amorphous phase where a limited amount of cellulose could be well mixed with PCL. A relatively large shift of the midpoint in the PCL glass transition region to the higher temperature side was noted at the compositions containing 20 and 30 wt% cellulose. This effect is discussed in relation to the requirement of an optimum balance in the density of the interacting hydroxyl and ester groups, for obtaining true miscibility of cellulosics with PCL at the molecular level.
Gelation in thermosets formed by chain addition polymerization
Authors: Heise M. S. , Martin G. C. , Gotro J. T.
Published: May 2005

The physical behavior of the diglycidyl ether of bisphenol A, cured with different concentrations of 2‐ethyl‐4‐methylimidazole, was examined with dynamic mechanical and dielectric analyses, differential scanning calorimetry, and solvent extraction studies, ‘The network formation process was shown to depend strongly on the imidazole concentration’. At high imidazole concentrations, the gel point was characterized by a decrease in sol fraction, the crossover of the dynamic moduli and a rapid increase in viscosity. At low imidazole concentrations, the viscosity remained low until the sol fraction approached zero. For this system, the gel point, which occurred prior to the dynamic moduli crossover, was characterized by comparing the thermal properties of the network with the viscosity and dielectric behavior of the resin system during cure.
Some properties of polyethylene compounds with surface‐modified fillers
Authors: Schreiber H. P. , Viau J.‐M. , Fetoui A. , Deng Zhuo
Published: May 2005

The dispersion of variously surface‐treated CaCo3 fillers in linear low density polyethylene has been studied, along with mechanical properties of the filled compounds. Microwave plasma discharges were used to modify the filler surfaces. Inverse gas chromatographic analyses showed that plasma treatments could change the dispersive and non‐dispersive components of filler surface characteristics. A reduction in these surface energies facilitated the dispersion of the filler in the non‐polar polyethylene. Mechanical properties, particularly those at high deformation of the filled plastic, also responded to filler surface treatments, the ductility at failure increasing with a decrease in the filler's surface polarity. For any given elongation at failure, it was found that the amount of filler accommodated by the host polymer was raised by the appropriate surface modification procedure. The work illustrates the important contribution made by interfacial phenomena to various performance aspects of complex polymer systems.
Detergent assisted stress cracking in low density polyethylene
Authors: Chang P. , Donovan J. A.
Published: May 2005

Igepal assisted environmental stress cracking (ESC) of LDPE has shown three characteristic regions with increasing crack driving force: Region I‐crack speed and craze length increased. Region II‐crack speed and duplex plastic zone length were constant, and Region Ill‐crack speed decreased while the deformation zone length increased. The activation energies for the three regions were 100, 23, 20 kJ/mole, respectively. The proposed rate controlling processes of ESC for the LDPE/Igepal system are: Region 1 is controlled by a;‐relaxation, and Region II and III are controlled by lamellar orientation. The Igepal plasticizes the amorphous phase and facilitates the stress induced orientation of the lamellar.
High temperature crystallization of poly(ethylene terephthalate)
Authors: Roland C. M.
Published: May 2005

Annealing poly(ethylene terephthalate) (PET) at high temperature results in a crystalline phase stable to 10°C higher than the temperature previously regarded as the equilibrium melting point. Melting temperatures as high as 289°C can be attained, which is equivalent to the equilibrium melting point determined herein for PET. The high melting point and tendency to superheat suggest that the crystals possess a substantial extended chain structure, notwithstanding the magnitude of the infrared fold band.
Injection molding of long fiber‐reinforced thermoplastics: A comparison of extruded and pultruded materials with direct addition of roving strands
Authors: Truckenmüller F. , Fritz H.‐G.
Published: May 2005

An injection molding process is proposed whereby roving strands are directly incorporated into the polymer melt by using a reciprocating‐screw‐plasticating unit. The direct incorporation of continuous fibers (DIF) offers the possibility to substitute the relatively expensive and limited pultrusion process currently used to produce long fiber pellets. In this preliminary study experimental investigations on glass fiber‐reinforced polyamide‐6,6 are carried out, starting with short and long fiber pellets in comparison to the direct incorporation of roving strands into the polymer melt. Some special aspects of the processing of long fiber‐reinforced thermoplastics are discussed. The results of fundamental mechanical and physical property investigations are presented, including fiber length distribution, fiber concentration, fiber bundling/clustering and fiber orientation. The influence of fiber diameter and fineness of strands (tex) on the feed‐in behavior and the resulting property profile is also discussed.
Studies on polyblends of poly(vinyl chloride) and acrylonitrile‐butadiene‐styrene terpolymer
Authors: Maiti S. N. , Saroop U. K. , Misra Ashok
Published: May 2005

Blends of poly (vinyl chloride) (PVC) and acrylonitrile‐butadiene styrene (ABS) terpolymer were prepared in different ratios by a melt blending technique. ABS containing three different levels of rubber content were used. A quantitative assessment of ABS in PVC/ABS blends has been shown by infrared studies. ABS content has been shown as the presence of the characteristic acrylonitrile peak. Differential scanning calorimetry (DSC) studies have been carried out to study the glass transition (Tg) behavior of the blends. Two Tg values corresponding to PVC and styrene‐acrylonitrile (SAN) copolymer have been observed. Thermogravimetric analysis (TGA) reveals a significant improvement in thermal stability of these blends as compared to PVC. Mechanical properties show a significant increase in the impact strength which is related to rubber content of the ABS used. Morphological studies have been carried out by scanning electron microscopy which support the observation that an increase in rubber content results in greater ductility.
Chemorheology of unfilled and filled epoxy resins
Authors: Ng Hendra , Manas‐Zloczower Ica
Published: May 2005

Filled thermosetting resins used for adhesives, sealants, and coatings are two‐phase systems whose rheological behavior is determined by the properties of both phases as well as by the interactions between the matrix and the filler. The chemorheological changes during the crosslinking of an epoxy system (EPON 828 with curing agent Y from Shell Chemical Co.) were investigated. The influence of an untreated silica filler on the reaction kinetics and the Rheological behavior of the system were also analyzed. The concentration of the filler was varied between 0 and 17.25 vol%. The influence of the filler on the gel point was explained in terms of the accelerating effect of the filler on the reaction kinetics.
The influence of knit‐lines on the tensile properties of fiberglass reinforced thermoplastics
Authors: Nadkarni V. M. , Ayodhya S. R.
Published: May 2005

The adverse effect of knit‐line formation on the mechanical properties of thermoplastics has been well documented for unfilled materials. A majority of these investigations concern amorphous polymers, whereas a number of engineering polymers are semicrystalline and also contain reinforcing fillers and fibers. The present investigation deals with the effect of knit‐lines on the mechanical behavior of unfilled and glass fiber‐reinforced semicrystalline polymers, such as polypropylene, poly(butylene terephthalate), poly(ethylene terephthalate), and poly(phenylene sulfide). Unfilled and fiber‐reinforced polystyrene was also investigated for reference. Tensile specimens with knit‐lines were produced by impinging melt fronts from two gates located at opposite ends of the dumbbell‐shaped mold. The effect of process conditions on the knit‐line strength was studied by varying primarily the melt and mold temperatures. The presence of glass fibers significantly reduced the knit‐line factor based on strength and strain to failure for the reinforced grades of all polymers relative to their respective unfilled grades. This is attributed to the lack of fiber flow across the knit‐line, which makes the material in the knit‐line region act as if it is not reinforced. The knit‐line strength could be changed through process modifications. For the unfilled grades of semicrystalline polymers, the presence of knit‐lines did not affect the yield strength but reduced the elongation at onset of necking, indicating that little spherulitic growth takes place across the knit‐line.
On the thermal behavior and mechanism of residual microstress buildup at the matrix interface in filled epoxy resins
Authors: Wang Hong‐Bing , Li Shan‐Jun , Yu Tong‐Yin
Published: May 2005

We have detailed the effects of annealing and temperature on the residual microstress at the matrix interface in rubber‐filled and glass bead‐filled epoxy resin systems. We found that annealing renders changes in residual microstress. The closer the annealing temperature to the glass transition temperature of the sample, the more pronounced the annealing effect on the stress. Also, we examined the interfacial residual microstress and found a linear relationship with annealing temperature. A description of the mechanism of the interfacial microstress buildup is proposed.
Morphology and permeability in extruded polypropylene/ethylene vinyl‐alcohol copolymer blends
Authors: Lohfink G. W. , Kamal M. R.
Published: May 2005

Studies of the morphology of extruded polymer blend systems have shown that it is feasible to produce a laminar structure of an ethylene vinyl‐alcohol copolymer (EVOH) dispersed phase in a polypropylene (PP) matrix phase. The laminar structure forms in the core of the extrudate when a slit die is incorporated into the extrusion process. Morphological studies, including a study of morphology development inside the die and studies of the effect of processing conditions on the morphology of the final product, revealed that the laminar structure is a result of die design. Processing conditions influence mainly the shape and dimensions of the laminar core region of the extrudate. Oxygen permeation tests have shown that the blend exhibits lower oxygen permeability than pure PP, when EVOH is incorporated as a dispersed phase into the system. Oxygen transmission rates obtained with a blend system approach those obtained with a multilayer coextrusion product, although only at high EVOH concentrations. Comparison of experimental data with theoretical permeation predictions shows that, up to 20 wt% EVOH, the reduction in oxygen transmission rate follows the prediction for a homogeneous system. At 25 wt%, a considerable decrease in oxygen transmission rate is noticeable, and the trend for higher EVOH contents is towards the behavior of a multilayer system.
Impact properties of short carbon fiber reinforced nylon 6.6
Authors: Ishak Z. A. Mohd. , Berry J. P.
Published: May 2005

The impact properties of injection‐molded nylon 6.6 composites containing different loadings of short carbon fibers have been studied using an instrumented falling weight impact tester (IFWIT). Analysis of the impact data using linear elastic fracture mechanics (LEFM) has enabled the evaluation of the critical strain energy release rate, Gc. Instrumentation of the impact machine has facilitated the determination of another fracture mechanic parameter, the fracture toughness, Kc. Both parameters are observed to increase with increasing volume fraction of fibers. Examination of fracture surfaces using scanning electron microscopy (SEM) has revealed that the main energy dissipative processes responsible for toughening the composites is the fiber pull‐out mechanism.
Thermal properties of poly(pivalolactone)
Authors: Beshouri Sharon M. , Grebowicz Janusz S. , Chuah Hoe H.
Published: May 2005

Polypivalolactone (PPVL) is a highly crystalline polyester formed either by nucleophilic or electrophilic ring‐opening polymerization of 2,2‐dimethyl‐β‐propiolactone, commonly known as pivalolactone (PVL). The thermal properties and crystallization kinetics of the polymer formed under reaction injection molding (RIM) conditions were studied. The crystallization kinetics of PPVL were measured using differential scanning calorimetry (DSC), and Avrami theory was used to interpret the bulk crystallization kinetics. A comparison was made with commercially prepared PPVL. The kinetics data indicate laboratory prepared PPVL, which is of lower molecular weight, has similar crystallization rates compared to the higher molecular weight commercial material. The kinetics data also indicate the rate of crystallization is relatively rapid overall for PPVL, with low activation energies of crystallization. The calorimetric studies also utilized DSC and simultaneous ther‐mogravimetric analysis/differential scanning calorimetry (TGA/DSC). Thermal analysis showed a clear difference in melting behavior between high and low molecular weight material, possibly a reflection of the presence of the α and γ‐crystal forms of the polymer.
Diffusion of low molecular weight substances into a fiber with skin‐core structure—rigorous solution of the diffusion in a coaxial cylinder of multiple components
Authors: Fukuda Mitsuhiro , Kawai Hiromichi
Published: May 2005

The diffusion equation of low molecular weight substances (penetrant) into a coaxial cylinder of multiple components (m) was formulated in general and solved rigorously. As the simplest but a practical case of m = 2, which corresponds to the diffusion of penetrant into fibrous material with skin and core structure, the diffusion of penetrant was analyzed in detail. That is, changes in the penetrant concentration distribution within the coaxial dual cylinder of skin and core components and the total amount of penetrant sorbed within the cylinder both with time after exposing the cylinder to atmosphere of fixed penetrant concentration of Cout were calculated with variation of the diffusion coefficient ratio (D1/D2) and the radius ratio (R2/R1), where D1 and D2 are the diffusion coefficients of penetrant in the core and the skin, and R2 and R1 are the radii of the fibrous material and the core, respectively. Keeping (R2/R1) at a constant value of 1.2 but varying (D1/D2) from 104 to 10−2, the penetrant concentration distribution was calculated and found to be much different particularly within the core between (D1/D2) > 1 and (D1/D2) < 1. The sorption curves were also found to deviate in their respective ways from that of Fickian curve of a homogeneous cylinder with (D1/D2) = 1 except at initial stage of sorption. Further, by keeping (D1/D2) constant but varying (R2/R1) from 1.1 to 1.5, the effects of relative skin thickness upon the sorption curve were studied.
Principal features of structural relaxation in glassy polymers. A Review
Authors: Mijović Jovan , Nicolais Luigi , D'amore Alberto , Kenny Jose M.
Published: May 2005

The principal features of models of structural relaxation in the glassy state were reviewed. The concepts of fictive temperature as the structural parameter and nonexponentiality and nonlinearity of structural relaxations were described. Various expressions for the structural relaxation time were presented and compared. One particular model was selected and utilized in a parametric optimization study of structural relaxation. Model predictions were checked against experimental results obtained by volumetric and calorimetric measurements.
Mechanism of shear modification of low density polyethylene
Authors: Van Prooyen M. , Bremner T. , Rudin A.
Published: May 2005

In this paper we address the aspects associated with shear modification of low density polyethylene by extrusion. By successive passes of the polymer through an extruder it can be shown that both the melt viscosity and melt elasticity are reduced by shear modification. These reversible variations are not accompanied by significant changes in molecular weight distribution. The major effects of extrusion are to decrease the amount of elastically effecitve material. Study of proton relaxation times at 150°C shows that the melt comprises regions of relatively ordered, entangled, and unentangled polymer. Shearing reduces the proportion of more ordered material. The elastically effective anchors that are reduced by shearing are regions with restricted segmental mobility rather than conventional entanglements or intermolecular knots. Successive extrusions produce a relatively small decrease in the number of such constraints to molecular motion. Repeated shearing has a diminishing effect on the proportion of more ordered material in the polyethlene melt. This parallels observations of the effects of repeated shear modification on the properties of polyethylene films and other extrudates.
Modeling of polypropylene degradation during reactive extrusion with implications for process control
Authors: Pabedinskas A. , Cluett W. R. , Balke S. T.
Published: May 2005

This paper presents the development of a model for free radical initiated polypropylene degradation during reactive extrusion that combines a kinetic model of the polypropylene degradation reaction with a simplified model of the melting mechanism in the extruder. The free radical initiated degradation of polypropylene is characterized by a narrowing of the molecular weight distribution (MWD) and a decrease in the molecular weight averages. A high temperature SEC is used to determine MWD's for three different commercially available polypropylenes degraded at various initiator concentrations in a 1.5 inch single screw extruder (L/D = 24:1). The predictions of the kinetic model alone and the combined kinetic‐melting model are compared with the experimentally determined MWD's and molecular weight averages for the degraded polypropylenes. The predictions of a modified kinetic model that includes the possibility of termination by combination are also examined. The kinetic‐melting model is found to provide significantly improved predictions of the experimentally determined MWD's and molecular weight averages in comparison to the original kinetic model. A viscosity‐molecular weight relationship is also developed, which is then used to determine the gain of the degradation process as a function of the initiator concentration from the molecular weight averages predicted by the kinetic‐melting model. Earlier work has shown such prior knowledge of the process gain can be used to significantly improve the performance of process control schemes for the degradation process.
Nonisothermal elongational behavior of blends with liquid crystalline polymers
Authors: La Mantia F. P. , Valenza A. , Scargiali F.
Published: May 2005

Measurements of melt strength and breaking stretching ratio of several blends of thermoplastic polymers with liquid crystalline polymers are presented. The melt strength behavior depends not only on the viscosity of the blends but also on the temperature dependence of the viscosity. In particular, even if the viscosities of the blends are, at the extrusion temperature, lower than that of the thermoplastic matrices, the melt strength can be larger than that of the pure thermoplastics if its viscosity‐temperature curve exceeds that of the matrices far from the solidification temperature. This behavior allows one to spin or film blow these blends despite the low viscosity.
Isocyanate trimerization kinetics and heat transfer in structural reaction injection molding
Authors: Viola G. G. , Schmeal W. R.
Published: May 2005

Guidelines are developed for molding large composite parts via structural reaction injection molding using glass preforms and polyisocyanurate resins. These are based on numerical simulations of the simultaneous heat transfer and reaction kinetics of a commercial system during and after mold filling. Premised requirements are that resin does not gel before the mold is filled, yet, reactions are sufficiently vigorous to approach completion. An existing mechanistic kinetic model is used and material parameters found from a chemical kinetics study employing an insulated cup. It is found desirable to use a high mold temperature and a low preform temperature in molding. Nondimensionalization of the governing equations reveals the existence of a Nusselt number (Nu), which describes the relative importance of heat transfer between resin and glass relative to thermal diffusion to the mold wall. With a Nusselt number of about 50 or higher it is possible to use the cooling capacity of the preform to extend gel time. The magnitude of Nu is influenced by part thickness, glass fraction, strand diameter, and flow velocity. Thus, the effect of the preform on extending resin gel time is within control of the molder.
Annealing effects in poly(phenylene sulfide) as observed by dynamic mechanical analysis
Authors: Scobbo J. J. , Hwang C. R.
Published: May 2005

Poly(phenylene sulfide) (PPS) is a semicrystalline engineering resin with exceptional solvent resistance and thermal performance. Properties such as these are directly related to the high crystallinity of PPS. In order to exploit its crystalline nature, PPS should be molded at a high tool temperature (hot oil tool) to allow for the highest crystallization rate, and therefore the highest percent crystallinity. Alternately, if a low mold temperature is used, the molded parts should be annealed. This latter process has been studied for injection molded neat PPS resin for various annealing temperatures. Two different grades of PPS were studied that represent cured and linear types. Samples were studied as‐molded, and annealed at 160, 180, 200 and 220°C. Increases in glass transition temperature were noted upon annealing. An increase in storage modulus was also noted for annealed samples. This increase persisted up to approximately the annealing temperature. Differential scanning calorimetry has been used to show that annealing PPS allows for a secondary crystallization to occur whereby an endotherm appears that corresponds to the secondary crystalline phase melting near the annealing temperature. As the annealing temperature is increased, the area of the endotherm increases. The secondary crystallization explains the higher storage modulus that persists up to the annealing temperature. These results are discussed in terms of crystallinity and overall effect on heat distortion temperature.
In‐line monitoring of molten polymers: Near infrared spectroscopy, robust probes, and rapid data analysis
Authors: Hansen Marion G. , Khettry Atul
Published: May 2005

The concept of improved product quality and reduced costs has revolutionized analytical techniques in the polymer industry. It has brought in‐line analysis to the forefront, with near infrared (NIR) spectroscopy proving to be a very viable technique for such operations. A system for continuous in‐line near infrared monitoring of molten polymer blends, copolymers, and polymer reactions is being developed. The ultimate objective is to use this monitoring system to develop feedback control for polymeric processes. Experiments on blends of polystyrene and poly(phenylene oxide) have been performed by using a flow cell, located at the exit port of a single‐screw extruder. Qualitative analysis of spectral data has been substantiated by a variety of quantitative (multivariate) techniques. Robust calibration models, suitable for on‐line predictions, have been developed. The success of in‐line process analysis depends on the performance of fiber‐optic probes that are inserted into the process stream. These probes normally succumb to the demands of the rigorous process environment, typical of polymeric processes, i.e., high temperatures, high pressures, and adverse chemical conditions. Design and development of fiber‐optic probes that are capable of withstanding such harsh conditions have also been undertaken. Results will be reported on the polymeric systems and optical probes.
Ballistic performance of polycarbonate/polyester and polycarbonate/styrene‐acrylonitrile microlayer sheets
Authors: Kohlman William G.
Published: May 2005

Extruded microlayer sheets of Polycarbonate/Polyester (PC/PCTG) and Polycarbonate/Styrene‐acrylonitrile (PC/SAN) were tested for ballistic performance. Composition of the microlayer sheets ranged from 60 to 100 percent polycarbonate. The number of layers in the approximately 3 mm thick sheets ranged from on for the blend control samples to 3713 layers in the PC/PCTG sheets. The normalized ballistic test results showed that some samples performed as well as as and slightly better than injection molded polycarbonate samples. The failure mechanism was affected by the composition and the number of layers. Increasing composition of polycarbonate and number of layers decreased the percent of brittle failures.
A comparative study on the electrochemical properties of ring‐substituted polyanilines
Authors: Dai Lizong , Xu Yiting , He Yunyou , Gal Jean‐Yves , Wu Huihuang
Published: May 2005

The redox behavior of polyanilines with ring‐substituted groups synthesized by chemical polymerization, poly‐2,5‐dimethoxyaniline (PDMAn), poly‐m‐chloroaniline (PmClAn) and poly‐o‐toluidine (POT), was studied and the morphology and crystal orientation of platinum particles deposited on these polymer membranes was compared. The oxidation of isopropanol on platinized polyaniline‐modified electrodes as a model reaction was also investigated to examine the electrocatalytic properties of the polymers. The results show that the first oxidation potential of the polymers increases in the following sequence: PDMAn, POT and then PmClAn, which can be explained in terms of the electronic and steric effects of ring‐substituted groups. The growth of Pt particles electrodeposited on doping‐state POT and PDMAn polymer membranes takes place by a ‘progressive nucleation mechanism’, but by an ‘instantaneous nucleation mechanism’ on PmClAn. Platinum crystallites trend towards preferred‐orientation and Pt (200) is the preferred face, but the degree of preferred orientation depends on the polymer. The oxidation potentials of isopropanol are located near 0.3 V, and the oxidation currents increase on platinized polymer‐modified electrodes, indicating that the interaction of polymer with Pt particles might improve the catalytic activity of Pt. Polyanilines act not only as dispersion media but also change the electronic properties of Pt crystalline grains. Copyright © 2005 Society of Chemical Industry
Synthesis of polyurethane cationomers with anil groups: intramolecular proton transfer in salicylideneanil structures
Authors: Buruiana Emil C , Olaru Mihaela , Strat Mitache , Strat Geta , Simionescu Bogdan C
Published: May 2005

Three new o‐hydroxy Schiff bases, 2‐chloromethyl‐N‐(2‐hydroxybenzilidene)aniline, 3‐(11‐bromoundecanoyloxymethyl)‐N‐(2‐hydroxybenzilidene)aniline and 4‐chloromethylphenyl (carbamoyloxymethyl‐2‐hydroxybenzylidene)aniline, used as quaternization agents for a polyetherurethane precursor based on poly(tetramethylene oxide) diol of 2000 g mol−1 average molar mass (PTMO), 2,4‐toluene diisocyanate and N‐methyldiethanolamine (1:3:2 molar ratio), have been synthesized in order to obtain polymeric films with fluorescent properties. The structure and the photochromic mechanism of the salicylideneanil units were investigated. The excited state intramolecular proton‐transfer process (ESIPT) with the cis‐ and trans‐keto isomers formation as intermediate compounds and the formation of a keto tautomer were evidenced by a large Stokes shifted emission (100 nm). Copyright © 2005 Society of Chemical Industry
Synthesis of a novel luminescent copolymer based on bisphenol A
Authors: Trad Hager , Jaballah Najmeddine , Majdoub Mustapha , Roudesli Sadok , Roussel Joseph , Fave Jean Louis
Published: May 2005

A new luminescent copolymer (BPAEt2‐BP; Scheme 1), with short alternating divinylbiphenyl units and O‐diethylated bisphenol A (BPAEt2), was synthesized via the Wittig reaction. The polymer is fully soluble in common organic solvents and has a number‐average molecular weight of 4600 g mol−1 with a polydispersity index of 1.79. The structure of the polymer was confirmed by 1H NMR, 13C NMR, FTIR and Raman analysis. Thermal analysis of the polymer showed good stability up to 280 °C. Furthermore, polymer film absorbs at 360 nm and emits in the blue at 426 and 451 nm. The band‐gap calculated from the UV‐vis spectrum was about 2.80 eV. A single‐layer device of the configuration indium tin oxide (ITO)/BPAEt2‐BP/Al has a relatively low turn‐on voltage of 3 V. Copyright © 2005 Society of Chemical Industry
An activated neodymium‐based catalyst for styrene polymerization
Authors: Wang Jing , Wu Yi‐Xian , Xu Xu , Zhu Han , Wu Guan‐Ying
Published: May 2005

Coordination polymerization of styrene with a ternary catalyst system composed of catalyst neodymium tricarboxylate (Nd), co‐catalyst Al(i‐Bu)3 (Al) and chlorinating agent trichloroethane (Cl) was carried out in cyclohexane. The effects of the catalyst system preparation procedure and of the reaction conditions on catalytic activity, molecular weight and molecular weight distribution of the resultant polymers were investigated. The catalytic activity depended mainly on the molar ratios of Al/Nd and of Cl/Nd and on the ageing temperature and polymerization temperature. High polymerization conversion and high catalytic activity could be obtained at high Al/Nd ratios and/or at high ageing temperature. The catalyst system exhibited high activity of 8.32 × 104 g polystyrene (mol Nd h)−1 at 50 °C. The molecular weight of the polymers obtained reached high weight‐average (Mw) values (Mw = 4.35 × 105 g mol−1) when Al/Nd = 8, but relatively low values (6000–11 000 g mol−1) at high Al/Nd ratios. Copyright © 2005 Society of Chemical Industry
Supported zirconocene catalyst for preventing reactor fouling in ethylene polymerization
Authors: Entezami Ali , Najafi Moghadam Peyman
Published: May 2005

The commercial interest of metallocene complexes for olefin polymerization has led to additional efforts to prepare suitable metallocene complexes efficiently and economically. Ethylene polymerization was carried out with a series of heterogeneous catalysts which were prepared in various Zr/silica ratios by immobilization of Ind2ZrCl2 preactivated with methylaluminoxane (MAO) on silica. This method to form the catalyst system resulted in a polymerization catalyst with reduced fouling tendencies and improved reactor operability. Polymerization of ethylene was conducted in Buchi reactors in a slurry phase under mild pressure. Some of the physical properties of the obtained polymers were also determined. Copyright © 2005 Society of Chemical Industry
Intramolecular hydrogen bonding in o‐hydroxyaryl Schiff bases
Authors: Filarowski Aleksander
Published: May 2005

This review deals with selected aspects of research on o‐hydroxyaryl Schiff bases. Special attention is given to results obtained by x‐ray, IR, UV and NMR spectroscopic methods and quantum‐mechanical calculations that allow a better understanding of the nature of o‐hydroxyaryl Schiff bases. The paper reports on studies of sterically modified o‐hydroxyaryl Schiff bases with an intramolecular hydrogen bond made short owing to steric repulsion. The following points are focused upon: structural and energetic analysis of the steric effect and its influence on the hydrogen bond length; proton localization and the proton transfer process; the impact of proton transfer on the chelate and phenol rings in the intramolecular hydrogen bond; a generalized scheme of tautomer equilibrium and its study with the use of experimental and theoretical methods; some discrepancies found in standard parameters for a particular tautomeric form; calculations of the potential energy curve for basic tautomer forms; influence of the steric effect on the potential curve shape; and a review of semi‐empirical and quantum‐mechanical calculations of molecular structures in the ground state. Copyright © 2005 John Wiley & Sons, Ltd.
Steric and aromatic impact on intramolecular hydrogen bonds in o‐hydroxyaryl ketones and ketimines
Authors: Filarowski Aleksander , Kochel Andrzej , Cieslik Katarzyna , Koll Aleksander
Published: May 2005

X‐ray measurements at 100 K and quantum‐mechanical calculations showed a domination of the enol (OH) form in o‐hydroxyaryl ketones [6‐methoxy‐2‐hydroxyacetophenone (6OMeK), 4‐methoxy‐2‐hydroxyacetophenone (4OMeK), 5‐chloro‐4‐methyl‐2‐hydroxybenzophenone (5Cl4MeK) and 2‐hydroxyacetonaphthone (o‐HAN)], whereas a prevailing proton‐transfer (NH) form was found in o‐hydroxyacetonaphthylimine [2‐(N‐methyl‐α‐iminoethyl)naphthol (o‐HIN)]. The effective mechanism of the reduction in hydrogen bridge length due to steric repulsion in the o‐hydroxyaryl ketones is presented. The following phenomena were found: a decrease in phenol ring aromaticity caused by the proton‐transfer process, dependence of the HOMA index of aromaticity on the HOSE index defining the destabilization of the chelate ring and a dependence of the HOMA index on the lengths of the carbonyl bonds. Moreover, a correlation between phenol ring aromaticity [HOMA(phenol)] and the pseudo‐aromatic ring [HOSE(chelate)] is shown. Correlations between structural parameters of the chelate ring [d(C—O), d(Caryl—Calkyl)] and aromatic rings [HOMA(phenol)] of the o‐hydroxyaryl ketimines and ketones are presented. Copyright © 2005 John Wiley & Sons, Ltd.
Structural modifications resulting from proton transfer in complexes of phenols with pyridine
Authors: Majerz Irena , Kwiatkowska Emilia , Koll Aleksander
Published: May 2005

The structural consequences of proton transfer in complexes of phenol (1), 2,6‐dichlorophenol (2), 4‐nitrophenol (3) and 2,6‐dichloro‐4‐nitrophenol (4) with pyridine were analyzed on the basis of results of B3LYP/6–31G** calculations. Three methods of describing the progress of proton transfer are proposed: the O—H [d(OH)] and C—O [d(CO)] bond lengths and the fraction XPT of the proton transfer form, calculated from the values of the dipole moments. The d(OH) parameter reveals behaviour near to XPT and can be used as a universal measure of the degree of proton transfer. The d(CO) parameter gives nearly linear dependences for various structural parameters, but independent estimation of the specific effects of the substituents is necessary, as separate correlations for each complex are found. A role of resonance interaction in systems containing a p‐NO2 substituent is demonstrated. Copyright © 2005 John Wiley & Sons, Ltd.
Kinetics of base‐catalysed ring closure of methyl 2,6‐dinitrophenylsulfanylethanoate
Authors: Janík Marek , Štěrba Vojeslav , Černý Jiří , Macháček Vladimír , Jansa Petr
Published: May 2005

The base‐catalysed ring closure of methyl 2,6‐dinitrophenylsulfanylethanoate gives 2‐methoxycarbonyl‐7‐nitrobenzo[d]thiazole‐3‐oxide. The kinetics of this ring closure were studied by means of UV–visible spectrophotometry in methanolic buffers of N‐methylmorpholine–N‐methylmorpholinium chloride and N‐methylpiperidine–N‐methylpiperidinium chloride at 25°C at ionic strength I = 0.1 mol l−1. The dependences of kobs on the base concentration are not linear, their slopes decreasing with increasing base concentration at constant ratio of the buffer components. The reaction mechanism was suggested on the basis of comparison with the ring closure kinetics of methyl 2,4,6‐trinitrophenylsulfanylethanoate. The rate‐limiting step of the reaction sequence consists in formation of the conjugated base of substrate 1. Copyright © 2005 John Wiley & Sons, Ltd.
Estimation of reactivity ratios of acrylate copolymers by 1H‐NMR
Authors: Nithianandam V. S. , Kaleem K. , Srinivasan K. S. V. , Joseph K. T.
Published: May 2005

Copolymers of methyl methacrylate (MMA) and dimethylaminomethacrylate (DMAEM) are useful for binding of enzymes. Copolymerization of MMA and DMAEM was carried out in dioxane using benzoyl peroxide as an initiator at 70°C. The estimation of the composition of MMA and DMAEM in copolymer was carried by 1H‐NMR. The reactivity ratio was found to be r1 = 1.20 and r2 = 0.19 by Kelen‐Tüdös method and r1 = 1.24 and r2 = 0.21 by Finemann‐Ross method.
Network formation during vinyl polymerization via inorganic particles
Authors: Nagata K. , Turner D. T.
Published: May 2005

Methyl methacrylate containing a small amount of 4‐methacryloxyethyl trimellitate anhydride (1.0–1.5 wt %) yielded an insoluble network when polymerized in the presence of various inorganic powders, such as lithium aluminum silicate. This unexpected result was obtained for polymerization initiated either by exposure to γ‐rays or by heating with azobisisobutyronitrile. In contrast, polymerization in the absence of inorganic powder gave the expected soluble products. Therefore, it is concluded that the inorganic particles play a role in network formation. In order to account for network formation even in a supernatant layer of clear monomer, i.e., above the centrifuged sedimentation volume of the powder, it is suggested that the monomer reacts on the surface of particles to form a diffusive crosslinking agent.
Synthesis and properties of poly(cis‐1,4‐dihydroxy‐2,3‐epoxybutane)
Authors: Vandenberg E. J.
Published: May 2005

The cyclic acetone ketal of 1,4‐dihydroxy‐2,3‐epoxybutane (DMTO) polymerizes with i‐Bu3Al‐0.7 H2O catalyst by a cationic mechanism at −78°C to a moderate molecular weight (ηinh up to 0.7), atactic (based on 13C‐NMR) polymer (PDMTO). At higher temperature and in bulk, up to 14% crosslinked polymer is obtained as a result of epoxide and ketal ring opening. Triethylaluminum is an effective catalyst at 0–50°C in bulk. Coordination catalysts were less effective but the results indicate that an effective one can be designed. PDMTO is readily hydrolyzed with aqueous HCl treatment to atactic, water‐soluble poly(1,4‐dihydroxy‐2,3‐epoxybutane) (PDHEB) with a Tg of 80°C. PDHEB is melt stable to 200°C and can be molded to give brittle, clear films that readily pick up 5–10% H2O from the atmosphere to give properties like those of plasticized poly(vinyl chloride). PDHEB is degraded by electron beam radiation but can be crosslinked with glyoxal plus toluene sulfonic acid/The bis(trimethylsilyl) ether of cis‐1,4‐dihydroxy‐2,3‐epoxybutane was polymerized cationically with the i‐Bu3Al‐0.7 H2O catalyst at −78°C to a fairly tactic, presumably racemic di‐isotactic, amorphous polymer, with ηinh of 0.16. A mechanism is proposed for this stereoregular polymerization based on a complexation of the Si side group of the last chain unit with the propagating oxonium on.
Structure and phase transitions in poly(diethylsiloxane)
Authors: Ya. Tsvankin D. , Papkov V. S. , Zhukov V. P. , Godovsky Yu. K. , Svistunov V. S. , Zhdanov A. A.
Published: May 2005

The structure changes accompanying phase transitions in poly(diethylsiloxane) (PDES) have been studied by WAXS and SAXS techniques using oriented and isotropic samples. PDES may exist in two low‐temperature modifications (the monoclinic α1‐form and presumably the “tetragonal” β1‐form) and two high‐temperature modifications (the monoclinic α2‐form and the “tetragonal” β2‐form). In linear PDES the crystal ‐ crystal transitions α1–α2 and β1–β2 occur near 214 and 206 K, respectively. At higher temperatures α2 (280 K) and β2 (290 K) forms transform into the mesomorphic phase αm that gradually melts at 280–300 K giving an amorphous phase. According to x‐ray and density data, αm phase is also characterized by monoclinic structure slightly different from hexagonal packing.
Atom transfer radical copolymerizationof acrylonitrile/n‐butyl acrylate: Microstructure determination by two‐dimensional nuclearmagnetic resonance spectroscopy
Authors: Brar A. S. , Saini Tripta
Published: May 2005

Atom transfer radical polymerization conditions were optimized and standardized with different initiator and catalyst systems. Acrylonitrile/n‐butyl acrylate copolymers were synthesized with 2‐bromopropionitrile as the initiator and CuCl/Cu(0)/2,2′‐bipyridine as the catalyst system. Variations of the feed composition led to copolymers with different compositions. The number‐average molecular weight and the polydispersity index were determined by gel permeation chromatography. Quantitative 13C{1H} NMR was employed to determine the copolymer composition. The reactivity ratios calculated with a methodology based on the Mao–Huglin terminal model were rA = 1.30 and rB = 0.68 for acrylonitrile and n‐butyl acrylate, respectively. The reactivity ratios determined by the modified Kelen–Tudos method were rA = 1.29 ± 0.01 and rB = 0.67 ± 0.01. 13C{1H} NMR and distortionless enhancement by polarization transfer (DEPT‐45, 90, and 135) were used to distinguish methyl, methylene, methine, and quaternary carbon resonance signals. The overlapping and broad signals of the copolymers were assigned completely to various compositional and configurational sequences by the correlation of one‐dimensional (1H, 13C{1H}, and DEPT) and two‐dimensional (heteronuclear single quantum coherence, total correlation spectroscopy, and heteronuclear multibond correlation) NMR spectral data. The complete spectral assignments of carbonyl and nitrile carbons were performed with the help of heteronuclear multibond correlation spectra. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2810–2825, 2005
Environmentally responsive micelles from polystyrene–poly[bis(potassium carboxylatophenoxy)phosphazene] block copolymers
Authors: Chang Youngkyu , Powell Eric S. , Allcock Harry R.
Published: May 2005

Amphiphilic diblock copolymers that contained hydrophilic poly[bis(potassium carboxylatophenoxy)phosphazene] segments and hydrophobic polystyrene sections were synthesized via the controlled cationic polymerization of Cl3PNSiMe3 with a polystyrenyl–phosphoranimine as a macromolecular terminator. These block copolymers self‐associated in aqueous media to form micellar structures which were investigated by fluorescence spectroscopy, dynamic light scattering, and transmission electron microscopy. The size and shape of the micelles were not affected by the introduction of different monovalent cations (Li+, K+, Na+, and Cs+) into the stable micellar solutions. However, exposure to divalent cations induced intermicellar crosslinking through carboxylate groups, which caused precipitation of the ionically crosslinked aggregates from solution. This micelle‐coupling behavior was reversible: the subsequent addition of monovalent cations caused the redispersion of the polystyrene‐block‐poly[bis(potassium carboxylatophenoxy)phosphazene] (PS–KPCPP) block copolymers into a stable micellar solution. Aqueous micellar solutions of PS–KPCPP copolymers also showed pH‐dependent behavior. These attributes make PS–KPCPP block copolymers suitable for studies of guest retention and release in response to ion charge and pH. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2912–2920, 2005
Origin of the color of π‐conjugated columnar polymers: Poly(p‐n‐octylthiophenyl)acetylene prepared using a [Rh(norbornadiene)Cl]2 catalyst
Authors: Huang Kai , Tabata Masayoshi , Mawatari Yasuteru , Miyasaka Atsushi , Sato Eriko , Sadahiro Yoshikazu , Kashiwaya Yoshiaki , Ishii Kuniyoshi
Published: May 2005

Highly stereospecific polymerization of a novel sulfur containing aromatic acetylenes, that is, (p‐n‐octylthiophenyl)acetylene (pOctSPA), was successfully performed using the Rh complex, [Rh(norbornadiene)Cl]2‐TEA, catalyst in the presence of various solvents under mild conditions. The resulting polymers were characterized in detail by 1H NMR, ESR, laser Raman, diffuse reflective UV‐Vis (DRUV‐Vis), and wide angle X‐ray diffraction methods. The data showed that the resulting polymers bear cis‐transoid form, which can induce the cis‐to‐trans isomerization when the cis polymers are subjected to pressure at room temperature under vacuum, breaking rotationally the cis CC bonds in the main‐chain giving two kinds of π‐radicals, the so‐called cis radical and trans radical as the origin of a polymer magnet like a novel spin glass material. Further, the resulting cis poly(acetylene)s were found to have a helical main‐chain, which is packed in pseudohexagonal crystal called π‐conjugated columnar or nano π‐conjugated columnar as a novel color controllable material. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2836–2850, 2005