bluuebunny/crossref_metadata_2025 huggingface dataset:
Graft copolymers of lignin as hydrophobic agents for plastic (wood‐filled) composites
Authors: Adcock Timothy , Shah Vipul , Chen Meng‐jiu , Meister John J.
Published: May 2003

Poly[lignin‐g‐(1‐phenylethylene)] graft copolymers synthesized by free‐radical, graft copolymerization on lignin and verified by fractionation, infrared spectroscopy, and solubility change possess macromolecular surface activity as indicated by their capacity to form stable emulsions between incompatible fluid phases, to adhesively bond to wood surfaces, and to change the contact angle of water on coated wood. The surface activity of the copolymer changes with its composition. As the weight percent lignin in the copolymerization reaction product increases beyond 20 wt %, the amount of the emulsion phase formed in a water–benzene mixture decreases. Maple wood flour could be solvent‐coated with a copolymer and both coated and uncoated maple flour could be extruded through a stranding plate into a wood‐filled composite with polystyrene. Physical property tests show that composite control samples are about 3% stiffer and less deformable than are the copolymer composites when dry and about 5 or more percent more deformable than are the copolymer composites when wet, showing that the copolymer coating increased the wet strength. The copolymer samples are always denser than are the controls. Copolymer coating on wood filler decreases the swelling in the composite, the partial molar volume of the imbibed water, and the dimensional change in the solid. These effects cause increase in the density of the copolymer composite upon imbibition of water. Coating the wood component of the composite with a copolymer creates a hydrophobic barrier that produces a decrease in water imbibition into the composite, which will not disappear in 20 or more years of water immersion. Expansion in water is highly dependent on the direction of extrusion. The length expands about 1%, the width expands about five times as much, and the thickness expands over 10 times as much as does the length. This differential expansion may be due to the 22% reduction in the width and a 71% reduction in the thickness of the melt as it passes through the die and the alignment of the long axis of the fiber with the direction of flow through the die. The reaction product is a thermoplastic solid stable below 200°C and thermoformable at between 150 and 180°C. Products which contain between 10 and 50 wt % lignin are heterogeneous solids. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1266–1276, 2003
Synthesis and fluorescence in solution of polybenzimidazolylphenylenephthalamides
Authors: Fujimura T. , Tsuchiya M. , Koizumi T. , Ishimaru K. , Kojima T.
Published: May 2003

Six polybenzimidazolylphenylenephthalamides (PBIPPA), two meta/para isomers, and four meta/para isomers that had different distances between a benzimidazolyl and the adjacent benzimidazolyl in a polymer chain were synthesized. They were soluble in N,N‐dimethylacetamide. In addition to the fluorescence from the π → π* transition of isolated phenylbenzimidazole, a fluorescence from a chromophore complex in the grand state appeared in the fluorescence spectra, which was observed at higher concentrations. The concentration dependence of the intensity of the fluorescence was investigated in order to learn whether the chromophore complex was intermolecular or intramolecular. It was concluded that the chromophore complex is intramolecular, a conclusion supported by the viscometric results. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1412–1416, 2003
Acrylic rubber‐fluorocarbon rubber miscible blends: Effect of curatives and fillers on cure, mechanical, aging, and swelling properties
Authors: Abdul Kader M. , Bhowmick Anil K.
Published: May 2003

The cure characteristics and mechanical properties of gum and filled acrylic rubber (ACM), fluorocarbon rubber (FKM), and their blends of varying compositions were studied both under unaged and aged conditions. The rheometric study showed that optimum cure properties were obtained using a mixed curing system of blocked diamine, hexamethylenediamine carbamate (Diak #1), and ammonium benzoate. From varying the curing agents, the optimum levels of Diak #1 and ammonium benzoate were found to be 1.5 and 2.5 phr, respectively. The addition of different fillers and their loading influenced the cure properties, with increased torque and reduced scorch safety. The gum and filled 50:50 (w/w) ACM‐FKM showed overall performance in strength properties. Postcuring improved the strength of all the systems, especially the systems with a higher proportion of FKM. None of the properties changed significantly during aging of the blends. FKM and the blends containing a higher proportion of FKM were affected least by aging. Swelling of the blends was reduced by the addition of fillers. Dynamic mechanical thermal analysis showed a single tan δ peak corresponding to a single phase transition for both cured and filled blends. The storage modulus of the blend increased from the gum blend to the filled blend, indicating the presence of polymer‐filler interaction. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1442–1452, 2003
Synthesis and functionalities of poly(N‐vinylalkylamide). XIV. Polyvinylamine produced by hydrolysis of poly(N‐vinylformamide) and its functionalization
Authors: Yamamoto Kazuya , Imamura Yachiyo , Nagatomo Emi , Serizawa Takeshi , Muraoka Yoichiro , Akashi Mitsuru
Published: May 2003

The molecular weights of poly(N‐vinylformamide) [poly(NVF)] obtained by free‐radical polymerization were expanded from being in the range of thousands to hundreds of thousands. Primary amino groups were introduced by the hydrolysis of poly(NVF) under both acidic and basic conditions. After 2 h polyvinylamine [poly(VAm)] was given at 60°C under a 2N NaOH solution. The apparent activation energy of poly(NVF) hydrolysis was 61.8 kJ/mol. Furthermore, alkyl side chains were partly introduced by a polymer modification reaction in poly(VAm) with carboxylic acid, using WSC (water‐soluble carbodiimide) as the activating agent to produce the stimuli‐responsive poly(VAm) derivative. The effects of external stimuli such as temperature and pH on the phase‐transition behavior of the copolymers were then studied. The lower critical solution temperature at pH 12 decreased depending on the alkyl group content. The phase‐transition behavior of the resulting polymers was also found to vary depending on the side‐chain length of the alkyl groups. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1277–1283, 2003
Morphology of phase separated blends of poly(cyclohexyl methacrylate) with poly(vinyl acetate)
Authors: Serrano B. , Baselga J. , Esteban I. , Sesé L. M. , Piérola I. F.
Published: May 2003

Blends of poly(vinyl acetate) (PVAc) and poly(cyclohexyl methacrylate) (PCHMA) labeled by copolymerization with 4‐methacryloylamine‐4′‐nitrostilbene (Sb), with (1‐pyrenylmethyl)methacrylate (Py) or with 3‐(methacryloylamine)propyl‐N‐carbazole (Cbz), were prepared by casting dilute solutions in tetrahydrofurane (THF) or chloroform onto silanized glass plates. The resulting films were studied by epifluorescence microscopy, microfluorescence spectroscopy, DSC and optical microscopy. Epifluorescence micrography probes the chemical composition of the different regions in phase separated blends, with black areas corresponding to PVAc rich regions and colored areas corresponding to labeled PCHMA rich regions. The technique also visualizes primary and secondary morphologies, which depend on the composition of the polymer blend and on the casting solvent. Mixtures containing 80 wt % PCHMA show, in general, a bicontinuous primary morphology suggesting a spinodal demixing mechanism. Solvent effects are particularly relevant for 50% and 20% PCHMA samples showing morphologies composed of PCHMA rich domains, in a matrix of solvent‐dependent compositions. Samples cast from chloroform are more homogeneous and the matrix is always highly fluorescent. In contrast, the domains of samples cast from THF are heterogeneous in size and shape and the matrix is non‐fluorescent, being thus formed by nearly pure PVAc. Small voids are formed in the polymer‐air interface. They are submicrometric for THF cast films and disappear with annealing at 122°C. For chloroform cast samples they are much less frequent and appear well ordered, forming a mostly hexatic two dimensional network. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1284–1290, 2003
Migration of additives from food grade polyvinyl chloride (PVC) films: Effect of plasticization by polymeric modifiers instead of conventional plasticizers
Authors: Audic J.‐L. , Reyx D. , Brosse J.‐C.
Published: May 2003

Based on the static and dynamic mechanical properties of the corresponding blends, the compatibility of six thermoplastic elastomers with polyvinyl chloride (PVC) was investigated. A terpolymer of ethylene, vinyl acetate and carbon monoxide (EVACO) was shown to give the optimal properties for the processing of transparent, soft, PVC‐based films. FTIR spectroscopic analysis of EVACO plasticized blends clearly shows that the interactions involve the carbonyl groups of the VA and not of the CO monomer units. The migration phenomenon was studied on PVC based samples plasticized with di‐2‐ethylhexyladipate (DEHA) and EVACO in varying amounts. The overall migration (OM) was monitored by the weight loss percentage of the samples immersed into isooctane at 40°C. The specific migrations of DEHA (SMD) and epoxidized soybean oil (SME) were shown to be responsible for the overall migration (OM = SMD + SME). The weight percentages of DEHA and epoxidized soybean oil (ESO) were correlated to the excess of immersion temperature (40°C) over the varying glass transition temperature of the samples. The results are explained with respect to the plasticizing effect of the additives and to the permanency of the EVACO‐plasticization.. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1291–1299, 2003
Electrochemical capacitor composed of doped polyaniline and polymer electrolyte membrane
Authors: Ryu Kwang Sun , Wu Xianlan , Lee Young‐Gi , Chang Soon Ho
Published: May 2003

We prepared polyaniline doped with LiPF6 and HCl, respectively, using chemical methods. The electrode composite was attached to both sides of Al mesh, while the polymer electrolyte mixture was spread on a glass plate. Then, the polyaniline‐based redox supercapacitor was fabricated using two electrodes and a polymer electrolyte membrane. The electrochemical performance of the redox supercapacitor was investigated by using the charge/discharge method, cyclic voltometry, and impedance spectroscopy. The initial specific capacitance was ≈115 F/g and it retained ≈90 F/g even after 5000 cycles. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1300–1304, 2003
Reactive compatibilization of the poly(butylene terephthalate)–EVA blend by maleic anhydride. II. Correlations among gel contents, grafting yields, and mechanical properties
Authors: Kim Seon‐Jun , Kang Cheul‐Jung , Chowdhury Subhendu R. , Cho Won‐Jei , Ha Chang‐Sik
Published: May 2003

Correlations among the degree of crosslinking of ethylene vinyl acetate copolymer (EVA), the grafting yield of maleic anhydride (MAH) onto EVA, and the mechanical properties of the blends of poly(butylene terephtalate) (PBT) with EVA‐g‐MAH were investigated. The EVA was functionalized by melt grafting reaction in the presence of MAH and dicumyl peroxide (DCP) using a plasticorder. The grafting yield of MAH was increased by increasing the concentration of MAH and DCP. The flexural strength of PBT–EVA‐g‐MAH blends depends on both the grafting yield of MAH and the degree of crosslinking of EVA, while the crosslinked parts of EVA‐g‐MAH hindered rather than improved the tensile strength regardless of the increase of the grafting yield of MAH. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1305–1310, 2003
Study of poly(acrylamide‐co‐2‐acrylamido‐2‐methylpropane sulfonic acid) hydrogels made using gamma radiation initiation
Authors: Zhang Chi , Easteal Allan J.
Published: May 2003

Poly(acrylamide‐co‐2‐acrylamido‐2‐methylpropane sulfonic acid) hydrogels were synthesized using gamma‐radiation‐initiated polymerization. The progress of copolymerization and crosslinking was observed by viscosity measurement on reaction mixtures subjected to varying radiation doses. The copolymer gels were characterized by differential scanning calorimetry, X‐ray diffraction, scanning electron microscopy, infrared spectroscopy, and elemental analysis. The swelling behavior and other properties of the gels were found to be very similar to those of poly(acrylamide‐co‐2‐acrylamido‐2‐methylpropane sulfonic acid) hydrogels synthesized using conventional free‐radical initiation in the presence of crosslinkers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1322–1330, 2003
Rheokinetic modeling of HTPB–TDI and HTPB–DOA–TDI systems
Authors: Bandgar B. M. , Sharma K. C. , Mukundan T. , Krishnamurthy V. N.
Published: May 2003

A study of the effect of temperature on a mixture of polymer and curative in the processing of rocket propellants is reported. Experimental viscosity of a hydroxyl‐terminated polybutadiene–toluene diisocyanate (HTPB–TDI) system was measured using a Brookfield viscometer model DV III. Viscosity showed dependence on temperature as well as time. The viscosity data of the HTPB–TDI system showed a linear relationship with temperature, with a change in slope at 45°C. The time dependence model showed a fourth‐order curve fit, which gave better results over the exponential model fit. The activation energy required for flow of the HTPB–TDI system was found to be 15.5 kJ/mol. Experimental viscosity measurements at various temperatures was also carried out on a hydroxyl‐terminated polybutadiene–dioctyl adipate –toluene diisocyanate (HTPB–DOA–TDI) system. The temperature dependence showed a decrease in viscosity with an increase in temperature up to 60 min, beyond which the viscosity increased. Viscosity showed a linear relation with temperature, with a change in the slope at 50°C instead of at 45°C for HTPB–TDI system. Beyond 50°C the data followed a polynomial model similar to that of the HTPB–TDI system, and the results matched well with the experimental data. The activation energy of the HTPB–DOA–TDI system increased with an increase in the binder weight ratio. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1331–1335, 2003
Increase of catalyst activity by transfer of bulky alkyl groups from zirconocene complexes to methylalumoxane
Authors: Denner Christine E. , Alt Helmut G.
Published: May 2003

The activity of metallocene catalysts in ethylene polymerization can be increased by a factor of up to 3.5 when the corresponding metallocene catalyst precursors possess one or two bulky alkyl ligands such as benzyl groups instead of the conventional chloro ligands. We assume that in the activation process with methylalumoxane (MAO) these bulky alkyl groups are transferred from the metal to the MAO cocatalyst. The actual cocatalyst is supposed to be a cage with one or more monomeric AlMe3 molecules inside. The bulky alkyl group is transferred to such an AlMe3 unit and can act as a spacer separating the catalytically active metallocenium cation from the MAO anion. This effect is supposed to be responsible for the increase in activity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1336–1340, 2003
Closed‐loop recycling of postused PP‐filled garden chairs using the restabilization technique. III. Influence of artificial weathering
Authors: Kartalis C. N. , Papaspyrides C. D. , Pfaendner R.
Published: May 2003

Artificial weathering was performed for 4000 h to evaluate the light stability of postused, CaCO3‐filled polypropylene material recycled from garden chairs. The old chair material was recycled by applying the remelting–restabilization technique while using different stabilization systems in selected concentrations. To study the role of restabilization in the material performance, the tensile impact strength was monitored during the artificial weathering exposure. The data were compared to microphotographs of the specimens' surfaces. The effect of light on the material was further studied through yellowness index (Y.I.) determinations. The results revealed that the appropriate restabilization of the postconsumer chair material is mandatory for improving its light stability, ensuring its reuse in the original application. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1311–1318, 2003
Effect of the polyurethane crystalline interphase formed at an Al surface on water‐vapor absorption
Authors: Kim Jangsoon , Ryba Earle R. , Bai Jianming
Published: May 2003

Water‐vapor absorption of polyurethane/Al bonds was studied, and the weight gain of samples after water‐vapor exposure was measured to examine the effect of the polyurethane crystalline interphase formed at the Al surface on water‐vapor absorption. Water‐vapor absorption was found to be independent of the crosslink density of the polyurethanes. Instead, it was found that the microstructural characteristics of the spherulitic interphase, a mixture of crystallites and amorphous material formed on the Al surface, strongly affects water‐vapor absorption: As the area fraction and the size of spherulites for the films increases, the amount of absorbed water vapor initially increases rapidly and then remained constant. The water vapor absorbed and condensed at spherulite boundaries consisting of voids and defects was created due to volume contraction during polymer crystallization.© 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1417–1422, 2003
Physical properties of wool fibers modified with isocyanate compounds
Authors: Freddi Giuliano , Innocenti Riccardo , Arai Takayuki , Shiozaki Hideki , Tsukada Masuhiro
Published: May 2003

Wool fibers were chemically modified with various kinds of isocyanates and diisocyanates. The reactivity of these modifying agents was examined as a function of the reaction solvent, temperature, time, and isocyanate chemistry. The use of dimethyl sulfoxide as the solvent, aliphatic mono and bifunctional isocyanates, such as dodecyl isocyanates and hexamethylene diisocyanate, and a temperature of 75°C resulted in higher weight gains. The moisture content of wool fibers tended to decrease with increasing the weight gain, the extent of which depended on the isocyanate used. Monofunctional isocyanates caused a sharp drop of tensile strength and an increase of elongation at break, while bifunctional isocyanates preserved the intrinsic tensile properties of wool. The FTIR spectra showed changes in the amide I, II, and III ranges, in the CO stretching range at 1750–1700 cm−1, and in the CH stretching and bending regions at 3000–2800 and 1500–1350 cm−1, respectively, attributable to the incorporation of the modifying agent. DSC measurements highlighted remarkable changes in the thermal behavior of acylated wool fibers. The bimodal melting endotherm at 230–240°C shifted to lower temperature, and the relative intensity of the constituent peaks changed as a function of the weight gain. Foreign deposits adhering to the surface of chemically modified wool fibers were detected by SEM analysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1390–1396, 2003
Potentials in anionic polyelectrolyte hydrogels
Authors: Gao F. , Reitz F. B. , Pollack G. H.
Published: May 2003

Polyelectrolyte hydrogels perform interesting physical and chemical changes, such as motility and bend in the presence of electric fields and interaction with ionic surfactants. We think that ionizable groups of polyelectrolyte hydrogels play a vital role in these environments. In this work, we prepared three anionic polyelectrolyte hydrogels by two different routes, and micropipetts electrode was employed to determined negative potential in the gels. Our work showed that the gels reported herein all display a high degree of swelling with hydration and have a substantial negative potential in KCl solution and a simple mechanism was also described. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1319–1321, 2003
Synthesis and thermotropic liquid‐crystalline behavior of novel main‐chain poly(aryl ether ketones)
Authors: Hu Wei , Liu Baijun , Wang Dong , Yang Yanhua , Chen Chunhai , Jiang Zhenhua , Zhang Wanjin , Wu Zhongwen
Published: May 2003

Novel aromatic poly(ether ketones) containing bulky lateral groups were synthesized via nucleophilic substitution reactions of 4,4′‐biphenol and (4‐chloro‐3‐trifluoromethyl)phenylhydroquinone (CF‐PH) with 1,4‐bis(p‐fluorobenzoyl)benzene. The copolymers were characterized by differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction, and polarized light microscopy observation. Thermotropic liquid‐crystalline behavior was observed in the copolymers containing 40, 50, 60, and 70 mol % CF‐PH. The crystalline–liquid‐crystalline transition [melting temperature (Tm)] and the liquid‐crystalline–isotropic phase transition appeared in the DSC thermograms, whereas the biphenol‐based homopolymer had only a melting transition. The novel poly(aryl ether ketones) had glass‐transition temperatures that ranged from 143 to 151°C and lower Tm's that ranged from 279 to 291°C, due to the copolymerization. The polymers showed high thermal stability, and some exhibited a large range in mesophase stability. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1347–1350, 2003
Graft copolymerization of acrylic acid onto xanthum gum using a potassium monopersulfate/Fe2+ redox pair
Authors: Pandey Peeyoosh Kant , Banerjee Jaya , Taunk Kavita , Behari Kunj
Published: May 2003

A previously unreported graft copolymer of xanthan gum (XOH) with acrylic acid was synthesized and the reaction conditions were optimized using a potassium monopersulfate (PMS)/Fe2+ redox pair. Grafting ratio, add on, and conversion increase with an increase in the ferrous ion concentration (2.0 × 10−3 to 5.0 × 10−3 mol dm−3) and PMS concentration (1.0 × 10−3 to 4.0 × 10−3 mol dm−3). It was observed that grafting takes place efficiently when the acrylic acid concentration and temperature were 5.0 × 10−2 mol dm−3 and 35°C, respectively. Samples of xanthan gum and xanthan gum–g–acrylic acid were subjected to thermogravimetric analysis with the objective of studying the effect of grafting of acrylic acid on the thermal stability of xanthan gum. The graft copolymer was found to be more thermally stable than xanthan gum. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1341–1346, 2003
Influence of hydrophobe content on phase coexistence curves of aqueous two‐phase solutions of associative polyacrylamide copolymers and poly(ethylene glycol)
Authors: Abu‐Sharkh B. F. , Hamad E. Z. , Ali S. A.
Published: May 2003

The influence of hydrophobe content and type on the phase coexistence curves of aqueous two‐phase polymer systems containing poly(ethylene glycol) and associative polyacrylamide copolymers has been investigated. The top phase was poly(ethylene glycol)‐rich while the bottom phase was rich in the copolymer. Increased intramolecular association resulting from increased hydrophobe content was found to increase compatibility of the two polymers in the bottom phase. Large size asymmetry was found to be an important factor in determining the binodal curve. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1351–1355, 2003
The influence of various reaction parameters on the performance of (α‐diimine)nickel(II) catalysts in ethylene oligomerization reactions
Authors: Helldörfer Markus , Alt Helmut G.
Published: May 2003

Modified (α‐diimine)nickel(II) catalysts are suitable for ethylene oligomerization reactions. Due to the mechanism (“chain running”), the formation of double‐bond isomers and branched olefins can be observed. The obtained oligomer mixtures show a Schulz–Flory distribution. Increasing ethylene pressure favors the selectivity of α‐olefin formation. The same effect can be observed when Lewis bases like thiophene or furane are added to the oligomerization reaction mixture. These results can be related to an interaction of the additives with the catalytic active species during the oligomerization process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1356–1361, 2003
Calorimetric and rheological study of isocyanate–pyrolysis oil blends
Authors: Gagnon Mélany , Roy Christian , Rodrigue Denis , Riedl Bernard
Published: May 2003

The reaction of polymethylene diphenyl diisocyanate (pMDI) with pyrolysis oils (PO) was studied by differential scanning calorimetry (DSC) and rheology. Chemical reactions between pMDI and PO occur under 100°C, as shown in DSC scans. DSC analysis showed that the peak temperature of the reaction decreased as the PO content of the PO–pMDI blends increased. The heat of reaction is at its maximum around 30–40% PO content. A rheological study of various PO–pMDI blends was done to evaluate the evolution of viscosity with time for different PO–pMDI hybrid mixtures. The initial viscosity of the blends is directly proportional to the PO content. An exponential increase of viscosity was demonstrated for all PO–pMDI mixtures. Rheological and chemical analysis results confirmed that chemical reactions occur between pMDI and PO at room temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1362–1370, 2003
Synthesis, characterization, and rheological studies of methacrylic acid–ethyl acrylate–diallyl phthalate copolymers
Authors: Jassal Manjeet , Acharya Badri Narayan , Bajaj Pushpa
Published: May 2003

Copolymerization of methacrylic acid (MAA) and ethyl acrylate (EA) was performed by the emulsion polymerization technique in the presence of a mixture of ionic and nonionic emulsifiers, at 85°C, using potassium persulfate as initiator (0.16 wt % of monomer). The molar ratio of MAA : EA varied between 44 : 56 and 54 : 46 in the monomer feed. Copolymers of MAA and EA were synthesized by incorporating diallyl phthalate (DAP) with varying concentrations (0–1.7 mol % of total monomer) in the feed. A copolymer latex of MAA, EA, and DAP was also prepared by the variable feed process. The intrinsic viscosity and gel content were determined. Copolymers were characterized by IR and NMR spectroscopic techniques. The composition of copolymers was determined by 1H‐NMR spectra and sequential distribution from 13C{1H}‐NMR spectra. The pH of the copolymer emulsion varied between 3 and 10 by addition of aqueous ammonia (23% w/w) and its effect on Brookfield viscosity was studied. The effects of copolymer composition, crosslinking agent concentration in the feed, monomer feed process, polymer solid contents, and shear rate on Brookfield viscosity were studied at pH ∼ 8. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1430–1441, 2003
Physical properties of aliphatic polycarbonates made from CO2 and epoxides
Authors: Thorat Sudhir D. , Phillips Paul J. , Semenov Viktor , Gakh Andre
Published: May 2003

A homologous series of aliphatic polycarbonates with different side‐chain lengths was synthesized by ring‐opening polymerization of terminal epoxides with CO2 using zinc adipionate as catalyst [patented process of Empower Materials (formerly PAC Polymers Inc.)]. Additionally, a polycarbonate was made having a cyclohexane unit in its backbone, together with a terpolymer having both cyclohexane and propylene units. After characterization of thermal properties the aliphatic polycarbonates were found to be completely amorphous. Polycarbonates derived from long‐chain epoxides showed a glass‐transition temperature (Tg) below room temperature, whereas polycarbonates derived from cyclohexene oxide showed a Tg of 105°C, the highest yet reported for this class of polymers. The initial decomposition temperature of the polymers in air and nitrogen atmospheres was found to be less than 300°C. The mechanical properties and the dynamic mechanical relaxation behavior of the polymers were also reported. The effect of the chemical structure on the physical properties of aliphatic polycarbonates was discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1163–1176, 2003
Curing process of powdered phenol–formaldehyde resol resins and the role of water in the curing systems
Authors: He Guangbo , Riedl Bernard , Aït‐Kadi Abdellatif
Published: May 2003

The curing behavior of two kinds of commercial powdered resol phenolic resins was studied by differential scanning calorimetry. Liquid‐state 13C‐NMR spectroscopy was used to aid in understanding the curing behavior by detecting the structure of powdered resins. The reaction mechanism was interpreted with the dependency of activation energy on the degree of conversion. The results indicate that there are differences in the curing mechanism between core and face phenolic resins. The curing process of core resin was faster than that of face resin at the same reaction temperature. The water added in the curing system played an important role of plasticizer or diluent according to different curing stages and water content. In the initial curing stage, water mainly diluted the system and retarded the curing reactions. However, at the higher degrees of conversion, water played the role of plasticizer to decrease the effect of diffusion on the curing reactions to make the curing reactions more complete. The excess water added in the curing system played the role of diluent at almost all stages during the curing process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1371–1378, 2003
Structure and gas separation properties of composite films based on polyaniline
Authors: Orlov A. V. , Kiseleva S. G. , Karpacheva G. P. , Teplyakov V. V. , Syrtsova D. A. , Starannikova L. E. , Lebedeva T. L.
Published: May 2003

Composite films based on the polyvinyltrimethylsilane (PVTMS) with polyaniline (PANI) coating were obtained by borderline polymerization of aniline. The obtained coating was shown to differ from the polymer forming in the reaction mixture bulk both in chemical structure and morphology. Ratio and concentration of the reagents, mixing rate, reaction time, and condition of support surface were among the investigated factors affecting the growth and quality of PANI coating. The gas separation characteristics of composite membranes, as affected by the process conditions and the type of PANI, were investigated. It is shown that the proposed method provides a means for obtaining composite membranes that combine high selectivity, especially in O2/N2, He/CH4, and CO2/CH4 separation, with permeability higher than that of known composite materials. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1379–1384, 2003
Properties of impregnation resin added to multifunctional epoxy at cryogenic temperature
Authors: Chen Qiang , Gao Bingjun , Chen Jinglin
Published: May 2003

A multifunctional epoxy tetraglycidyl dibenzmethyldiamine and triglycidyl benzylamine were blended, respectively, into impregnation resin, which mainly consists of diglycidyl ether of bisphenol A (DGEBA) and acid anhydride hardener. This resin is expected to impregnate HT‐7U superconducting Tokamak toroidal field coils and improve the fracture toughness of DGEBA–acid anhydride resin at cryogenic temperature. However, the experimental results reveal that resin lap shear strengths decrease remarkably both at ambient and liquid nitrogen temperatures. After blending multifunctional epoxy for several hours, its viscosity increased quickly at room temperature. The usable potting life is too short to impregnate large coils such as those used in fusion reaction. By FTIR the possible reason was investigated. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1385–1389, 2003
Imprinting evolution and the price of silence
Authors: Murphy Susan K. , Jirtle Randy L.
Published: May 2003

In contrast to the biallelic expression of most genes, expression of genes subject to genomic imprinting is monoallelic and based on the sex of the transmitting parent. Possession of only a single active allele can lead to deleterious health consequences in humans. Aberrant expression of imprinted genes, through either genetic or epigenetic alterations, can result in developmental failures, neurodevelopmental and neurobehavioral disorders and cancer. The evolutionary emergence of imprinting occurred in a common ancestor to viviparous mammals after divergence from the egg‐laying monotremes. Current evidence indicates that imprinting regulation in metatherian mammals differs from that in eutherian mammals. This suggests that imprinting mechanisms are evolving from those that were established 150 million years ago. Therefore, comparing genomic sequence of imprinted domains from marsupials and eutherians with those of orthologous regions in monotremes offers a potentially powerful bioinformatics approach for identifying novel imprinted genes and their regulatory elements. Such comparative studies will also further our understanding of the molecular evolution and phylogenetic distribution of imprinted genes. BioEssays 25:577–588, 2003. © 2003 Wiley Periodicals, Inc.
The architecture of polarized cell growth: The unique status of elongating plant cells
Authors: Baluška František , Wojtaszek Przemysław , Volkmann Dieter , Barlow Peter
Published: May 2003

Polarity is an inherent feature of almost all prokaryotic and eukaryotic cells. In most eukaryotic cells, growth polarity is due to the assembly of actin‐based growing domains at particular locations on the cell periphery. A contrasting scenario is that growth polarity results from the establishment of non‐growing domains, which are actively maintained at opposite end‐poles of the cell. This latter mode of growth is common in rod‐shaped bacteria and, surprisingly, also in the majority of plant cells, which elongate along the apical–basal axes of plant organs. The available data indicate that the non‐growing end‐pole domains of plant cells are sites of intense endocytosis and recycling. These actin‐enriched end‐poles serve also as signaling platforms, allowing bidirectional exchange of diverse signals along the supracellular domains of longitudinal cell files. It is proposed that these actively remodeled end‐poles of elongating plant cells remotely resemble neuronal synapses. BioEssays 25:569–576, 2003. © 2003 Wiley Periodicals, Inc.
Fanconi anaemia proteins: Major roles in cell protection against oxidative damage
Authors: Pagano Giovanni , Youssoufian Hagop
Published: May 2003

Fanconi anaemia (FA) is a cancer‐prone genetic disorder that is characterised by cytogenetic instability and redox abnormalities. Although rare subtypes of FA (B, D1 and D2) have been implicated in DNA repair through links with BRCA1 and BRCA2, such a role has yet to be demonstrated for gene products of the common subtypes. Instead, these products have been strongly implicated in xenobiotic metabolism and redox homeostasis through interactions of FANCC with cytochrome P‐450 reductase and with glutathione S‐transferase, and of FANCG with cytochrome P‐450 2E1, as well as redox‐dependent signalling through an interaction between FANCA and Akt kinase. We hypothesise that FA proteins act directly (via FANCC and FANCG) and indirectly (via FANCA, BRCA2 and FANCD2) with the machinery of cellular defence to modulate oxidative stress. The latter interactions may co‐ordinate the link between the response to DNA damage and oxidative stress parameters (3, 6–12). BioEssays 25:589–595, 2003. © 2003 Wiley Periodicals, Inc.
Species as family resemblance concepts: The (dis‐)solution of the species problem?
Authors: Pigliucci Massimo
Published: May 2003

The so‐called “species problem” has plagued evolutionary biology since before Darwin's publication of the aptly titledOrigin of Species. Many biologists think the problem is just a matter of semantics; others complain that it will not be solved until we have more empirical data. Yet, we don't seem to be able to escape discussing it and teaching seminars about it. In this paper, I briefly examine the main themes of the biological and philosophical literatures on the species problem, focusing on identifying common threads as well as relevant differences. I then argue two fundamental points. First, the species problem is not primarily an empirical one, but it is rather fraught with philosophical questions that require—but cannot be settled by—empirical evidence. Second, the (dis‐)solution lies in explicitly adopting Wittgenstein's idea of “family resemblance” or cluster concepts, and to consider species as an example of such concepts. This solution has several attractive features, including bringing together apparently diverging themes of discussion among biologists and philosophers. The current proposal is conceptually independent (though not incompatible) with the pluralist approach to the species problem advocated by Mishler, Donoghue, Kitcher and Dupré, which implies that distinct aspects of the species question need to be emphasized depending on the goals of the researcher. From the biological literature, the concept of species that most closely matches the philosophical discussion presented here is Templeton's cohesion idea. BioEssays 25:596–602, 2003. © 2003 Wiley Periodicals, Inc.
Biological activities of the shrub Salsola tuberculatiformis Botsch.: Contraceptive or stress alleviator?
Authors: Swart Pieter , Swart Amanda C. , Louw Ann , van der Merwe Kirsten J.
Published: May 2003

Plants belonging to the genus Salsola (Family: Chenopodiaceae) are common in the arid and semiarid regions of our planet with no less than 69 different Salsola species found in Namibia and the Republic of South Africa. This genus is used as a traditional medicine and aqueous extracts of Salsola have been used by Bushmen women as an oral contraceptive. Ingestion of the Namibian shrub Salsola tuberculatiformis Botsch. by pregnant Karakul sheep leads to prolonged gestation and fetal post‐maturity and, as a result, the pelts of the new‐born karakul lambs are worthless. This initiated an investigation into the active agents in the plant, using the terminal enzyme in adrenal corticosteroidogenesis, cytochrome P450‐dependent 11β‐hydroxylase (P450c11), as a bioassay. Although the active fraction, S2, was extremely labile, partial structure determination suggested the presence of synephrine and a highly reactive aziridine. Therefore a more stable analogue, 2‐(4‐acetoxyphenyl)2‐chloro‐N‐methylethylammonium‐chloride (compound A), was synthesised, which, like the active plant extracts, inhibited adrenal steroidogenesis and acted as a contraceptive. In addition, compound A was stabilised by interaction with steroid‐binding globulins in plasma thus enhancing biological activity in vivo. These findings provided explanations for the complex biological effects of the shrub as well as a new insight into the mode of action of chemically labile plant products in vivo. BioEssays 25:612–619, 2003. © 2003 Wiley Periodicals, Inc.
Dlg, Scribble and Lgl in cell polarity, cell proliferation and cancer
Authors: Humbert Patrick , Russell Sarah , Richardson Helena
Published: May 2003

Dlg (Discs large), Scrib (Scribble) and Lgl (Lethal giant larvae) are evolutionarily conserved components of a common genetic pathway that link the seemingly disparate functions of cell polarity and cell proliferation in epithelial cells. dlg, scrib and lgl have been identified as tumour suppressor genes in Drosophila, mutations of which cause similar phenotypes, involving disruption of cell polarity and neoplastic overgrowth of tissues. The molecular mechanisms by which Dlg, Scrib and Lgl proteins regulate cell proliferation are not clear, but there is some evidence that epithelial polarisation is required for this regulation. Dlg, Scrib and Lgl are highly conserved between human and Drosophila, and we discuss evidence that these proteins also play a role in cancer progression in humans. BioEssays 25:542–553, 2003. © 2003 Wiley Periodicals, Inc.
The thioredoxin‐like fold: Hidden domains in protein disulfide isomerases and other chaperone proteins
Authors: Clissold Patricia M. , Bicknell Roy
Published: May 2003

Although protein disulphide isomerase (PDI) has been known for nearly 40 years, several new PDIs have recently been described that reveal a remarkable diversity in both structure and function. This article reviews our current knowledge of the PDI family members and identifies four novel PDIs in the human genome. These include human transmembrane proteins that have C. elegans or Drosophila orthologues for which a developmental role has been proven. Their role in development, together with other functional roles for PDIs such as conferring resistance to apoptosis under hypoxia and a potential role in the oxygen‐sensing apparatus are discussed. Supplementary material for this article can be found on the BioEssays website (http://www.interscience.wiley.com/jpages/0265‐9247/suppmat/2003/25/v25.603.html). BioEssays 25:603–611, 2003. © 2003 Wiley Periodicals, Inc.
About face: Signals and genes controlling jaw patterning and identity in vertebrates
Authors: Richman Joy M. , Lee Sang‐Hwy
Published: May 2003

The embryonic vertebrate face is composed of similarly sized buds of neural crest‐derived mesenchyme encased in epithelium. These buds or facial prominences grow and fuse together to give the postnatal morphology characteristic of each species. Here we review the role of neural crest cells and foregut endoderm in differentiating facial features. We relate the developing facial prominences to the skeletal structure of the face and review the signals and genes that have been shown to play an important role in facial morphogenesis. We also examine two experiments one at the genetic level and one at the signal level in which transformation of facial prominences and subsequent change of jaw identity was induced. We propose that signals such as retinoids and BMPs and downstream transcription factors such as Distal‐less related genes specify jaw identity. BioEssays 25:554–568, 2003. © 2003 Wiley Periodicals, Inc.
Mitochondrial biogenesis: Which part of “NO” do we understand?
Authors: Leary Scot C. , Shoubridge Eric. A.
Published: May 2003

A recent paper by Nisoli et al.1 provides the first evidence that elevated levels of nitric oxide (NO) stimulate mitochondrial biogenesis in a number of cell lines via a soluble guanylate‐cyclase‐dependent signaling pathway that activates PGC1α (peroxisome proliferator‐activated receptor γ coactivator‐1α), a master regulator of mitochondrial content. These results raise intriguing possibilities for a role of NO in modulating mitochondrial content in response to physiological stimuli such as exercise or cold exposure. However, whether this signaling cascade represents a widespread mechanism by which mammalian tissues regulate mitochondrial content, and how it might integrate with other pathways that control PGC1α expression, remain unclear. BioEssays 25:538–541, 2003. © 2003 Wiley Periodicals, Inc.
The Ciona intestinalis genome: When the constraints are off
Authors: Holland Linda Z. , Gibson‐Brown Jeremy J.
Published: May 2003

The recent genome sequencing of a non‐vertebrate deuterostome, the ascidian tunicate Ciona intestinalis, makes a substantial contribution to the fields of evolutionary and developmental biology.1 Tunicates have some of the smallest bilaterian genomes, embryos with relatively few cells, fixed lineages and early determination of cell fates. Initial analyses of the C. intestinalis genome indicate that it has been evolving rapidly. Comparisons with other bilaterians show that C. intestinalis has lost a number of genes, and that many genes linked together in most other bilaterians have become uncoupled. In addition, a number of independent, lineage‐specific gene duplications have been detected. These new results, although interesting in themselves, will take on a deeper significance once the genomes of additional invertebrate deuterostomes (e.g. echinoderms, hemichordates and amphioxus) have been sequenced. With such a broadened database, comparative genomics can begin to ask pointed questions about the relationship between the evolution of genomes and the evolution of body plans. BioEssays 25:529–532, 2003. © 2003 Wiley Periodicals, Inc.
An improved model for analyzing the small angle x‐ray scattering of starch granules
Authors: Daniels D. R. , Donald A. M.
Published: May 2003

The structure of starch was studied using small‐angle x‐ray scattering (SAXS). The scattering data was modeled by considering a finite stack of alternating lamellae that are allowed to fluctuate both along the layer repeat direction and along the transverse layer direction. Analysis in this way of the SAXS data from starch allowed fresh insights into the native structure of several starch species, particularly potato starch. The novel model presented in this work was able to capture the experimentally observed SAXS patterns much better than previous models, which did not incorporate transverse layer fluctuations. © 2003 Wiley Periodicals, Inc. Biopolymers 69: 165–175, 2003
Structural characterization and artificial fiber formation of Bombyx mori silk fibroin in hexafluoro‐iso‐propanol solvent system
Authors: Zhao Chenhua , Yao Juming , Masuda Hiromi , Kishore Raghuvansh , Asakura Tetsuo
Published: May 2003

High‐resolution solution 13C‐NMR and CD studies of Bombyx mori silk fibroin revealed the presence of an ordered secondary structure 310‐helix, in hexafluoro‐iso‐propanol (HFIP). The solid‐state structure of the silk fibroin film prepared by drying it gently from the HFIP solution still keep the structure, 310‐helix, which was studied with high‐resolution solid state 13C‐NMR. The structural transition from the 310‐helix to silk II structure, heterogeneous structure including antiparallel β‐sheet, occurred during the artificial spinning from the HFIP solution. The wide‐angle x‐ray diffraction and differential scanning calorimetry thermograms of the artificial spinning fiber after postspinning treatments were observed together with the stress–strain curves. The results emphasize that the molecular structures, controlled morphology, and mechanical properties of the protein‐based synthetic polymers can be modulated for enhancing biocompatibility. © 2003 Wiley Periodicals, Inc. Biopolymers 69: 253–259, 2003
Acid‐induced denaturation of Escherichia coli ribonuclease HI analyzed by CD and NMR spectroscopies
Authors: Yamasaki Kazuhiko , Yamasaki Tomoko , Kanaya Shigenori , Oobatake Motohisa
Published: May 2003

Acid‐induced denaturation of the ribonuclease HI protein from Escherichia coli was analyzed by CD and NMR spectroscopies. The CD measurement revealed that the acid denaturation at 10°C proceeds from the native state (N‐state) to a molten globule‐like state (A‐state), through an apparently more unfolded state (UA‐state). In 1H–15N heteronuclear single‐quantum coherence (HSQC) spectra, cross peaks from the N‐state and those from the other two states are distinctively observed, while the UA‐state and A‐state are not distinguished from each other. Cross peaks from the UA/A‐states showed a small pH dependence, which suggests a similarity in the backbone structure between the two states. The direct hydrogen–deuterium (H–D) exchange measurement at pH with the largest population of UA‐state revealed that at least α‐helix I is highly protected in the structure of the UA‐state. A pH‐jump H–D exchange analysis showed that the protection of α‐helix I is highest also in the A‐state. The profile of hydrogen‐bond protection indicated that the structure of the A‐state is closely related to that of the kinetic folding intermediate. © 2003 Wiley Periodicals, Inc. Biopolymers 69: 176–188, 2003