bluuebunny/crossref_metadata_2025 huggingface dataset:
pH‐sensitive acrylic‐based copolymeric hydrogels for the controlled release of a pesticide and a micronutrient
Authors: Rudzinski Walter E. , Chipuk Timothy , Dave Ashok M. , Kumbar Sangamesh G. , Aminabhavi Tejraj M.
Published: November 2002

Acrylic‐based copolymers of methyl methacrylate (MMA) and methacrylic acid (MAA) have been prepared by solution and bulk polymerization techniques using benzoyl peroxide (BPO) as an initiator. Three polymers were prepared with a varying ratio of MMA/MAA. In an effort to increase the hydrophilicity of the matrix, one MMA/MAA polymer was prepared by adding an additional amount of 2‐hydroxy ethyl methacrylate (HEMA). All the polymers were crosslinked in situ by ethylene glycol dimethacrylate (EGDMA). These polymers were characterized by Fourier transform infrared spectroscopy and differential scanning calorimetry. Viscous flow characteristics were determined from solution viscosity and rheological measurements. Dynamic and equilibrium swelling experiments were carried out under varying pH conditions (i.e., 0.1N NaOH, 0.1N HCl, and double‐distilled water). Partially crosslinked hydrogels show varying hydrophilicity because of the presence of carboxylic acid groups making them pH‐responsive. Swelling increased with an increasing number of —COOH groups on the polymer backbone and the hydrophilicity varied with changing pH. Cypermethrin, a widely used pesticide, and cupric sulfate, a model micronutrient, were loaded into these pH‐sensitive hydrogels to investigate their controlled release characteristics. The in vitro release rates of both compounds have been carried out under static dissolution conditions at 30°C. Release data have been fitted to an empirical relation to estimate transport parameters. The release results have been discussed in terms of the varying hydrophilicity of the hydrogel network polymers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 394–403, 2003
Preparation of silicon‐/phosphorous‐containing epoxy resins from the fusion process to bring a synergistic effect on improving the resins' thermal stability and flame retardancy
Authors: Liu Ying Ling , Chiu Yie Chan , Wu Chuan Shao
Published: November 2002

Epoxy resins containing both phosphorous and silicon were prepared via the fusion process of reacting a phosphorous diol and a silicon diol with a bisphenol‐A‐type epoxy. With various feeding ratios of the reactants, epoxy resins with different phosphorous and silicon contents were obtained. Through curing the epoxies with diaminodiphenylmethane, the cured epoxy resins exhibit tailored glass transition temperatures (159–77°C), good thermal stability (>320°C), and high char yields at 700°C under air atmosphere. The high char yield was demonstrated to come from the synergistic effect of phosphorous and silicon, where phosphorous enriches char formation and silicon protects the char from thermal degradation. Moreover, high flame retardancy of the epoxy resins was found by the high LOI value of 42.5. The relationship of the char yields at 700°C under air atmosphere (ρ) and the LOI values of the epoxy resins could be expressed as LOI = 0.62ρ + 19.2. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 404–411, 2003
Tensile deformation mechanisms of polypropylene/elastomer blends reinforced with short glass fiber
Authors: Chin Tjong Sie , Xu Shi‐Ai , Li Robert Kwok Yiu , Mai Yiu‐Wing
Published: November 2002

Polypropylene hybrid composites reinforced with short glass fiber (SGF) and toughened with styrene–ethylene butylenes–styrene (SEBS) elastomer were prepared using extrusion and injection‐molding techniques. Moreover, hybrids compatibilized with SEBS‐grafted maleic anhydride (SEBS‐g‐MA) and hybrid compatibilized with PP grafted with maleic anhydride (PP‐g‐MA) were also fabricated. The matrix of the latter hybrid was designated as mPP and consisted of 95% PP and 5% PP‐g‐MA. Tensile dilatometry was carried out to characterize the fracture mechanisms of hybrid composites. Dilatometric responses showed that the elastic deformation was the dominant deformation mechanism for the SGF/SEBS/PP and SGF/SEBS‐g‐MA/PP hybrids. However, cavitation deformation prevailed over shearing deformation for both hybrids at the higher strain regime. The cavitation strain resulted from the debonding of glass fibers and from the crazing of the matrix in the SGF/SEBS/PP hybrid. In contrast, the cavitation was caused by the debonding of SEBS particles from the matrix of the SGF/SEBS‐g‐MA/PP hybrid. The use of PP‐g‐MA resulting in elastic deformation was the main mode of deformation in the low‐strain region for the SGF/SEBS/mPP and SEBS/SEBS‐g‐MA/mPP hybrids; thereafter, shearing appeared to dominate at the higher strain regime. This was attributed to the MA functional group improving the bonding between the SGF and PP. The correlation between fracture morphology and dilatometric responses also is presented in the article. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 441–451, 2003
Water‐soluble cationic polymers and their polymer–metal complexes with biocidal activity: A genotoxicity study
Authors: Rivas Bernabé L. , Pereira Eduardo D. , Mondaca María A. , Rivas Rodrigo J. , Saavedra Margarita A.
Published: November 2002

Water‐soluble polyelectrolytes containing ammonium and sulfonic groups, their polymer–Ag(I) complexes, and silver nitrate were investigated as bactericidal compounds for Staphylococcus aureus (Collection No. ATCC 28922) and Escherichia coli (Collection No. 6538P) according to the National Committee for Clinical Laboratory Standards (NCCL) method. All the compounds, except Ag(I), showed bactericidal activity only for S. aureus. Ag(I) showed high bactericidal activity for both bacteria. No important effect of the molecular weight or macromolecular size on the maximum bactericidal concentration value was observed. The genotoxicity was studied using the rec assay. None of the macromolecular compounds showed genotoxicity, except silver ions, whose value was borderline. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 452–457, 2003
Photografting of N‐isopropylacrylamide on polyethylene film in mixed solvents composed of water and organic solvent
Authors: Suka Irwan Ginting , Kuroda Shin‐Ichi , Kubota Hitoshi , Kondo Takashi
Published: November 2002

The effects of a mixed solvent consisting of water and organic solvents such as acetone and methanol on the photografting (λ > 300 nm) of N‐isopropylacrylamide (NIPAAm) on linear low‐density polyethylene film (thickness = 30 μm) was investigated at 30°C and 60°C. Xanthone, which had been coated on the film, was used as a photoinitiator. The photografting initiated even in the system at 30°C by using a longer irradiation time. It was found that the maximum percentage of grafting was attained at a certain concentration of organic solvent in the mixed solvent, which shifted to a lower concentration of organic solvent in the system at 60°C compared with the system at 30°C. It was found that the grafted chains of the sample prepared in the system with the higher polymerization temperature and the use of mixed solvent penetrated into the center of the film compared with the sample prepared in the system with the lower polymerization temperature and use of a water solvent. Moreover, the NIPAAm‐grafted films exhibited temperature responsiveness, swelling and shrinking in water at 0°C and 50°C, respectively. The extent of this characteristic was found to be closely related to the location of the grafted chains in film substrate, which was measured by an attenuated total reflection infrared spectroscope and a scanning electron microscope. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 458–463, 2003
In situ fast transient fluorescence technique (FTRF) to study swelling of gels made of various crosslinker contents
Authors: Erdoǧan M. , Pekcan Ö.
Published: November 2002

The fast transient fluorescence technique (FTRF), which uses the strobe master system (SMS), was employed to study the swelling of disc‐shaped PMMA [poly(methyl methacrylate] gels. Seven gels were prepared by free radical copolymerization (FCC) of methyl methacrylate (MMA) with various ethylene glycol dimethacrylate (EGDM) contents. Pyrene (Py) was introduced as a fluorescence probe during polymerization. After drying these gels, swelling experiments were performed in chloroform at room temperature. Py lifetimes were measured from fluorescence decay traces during the in situ swelling experiments. An equation was derived for low quenching efficiencies to interpret the behavior of lifetimes in the gel during swelling. It was observed that Py lifetimes in the gel decreased as swelling proceeded. The Li–Tanaka equation was used to determine the cooperative diffusion coefficients, Dc, which were found to decrease as the crosslinker content was increased. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 464–472, 2003
High‐resolution 13C–nuclear magnetic resonance study of heterogeneous amorphous polymers
Authors: Tavares Maria Inês Bruno
Published: November 2002

The combination of solid‐state nuclear magnetic resonance (NMR) techniques is very helpful for examining the behavior of heterogeneous amorphous polymers. With the magic‐angle spinning (MAS) technique, employing special conditions, only the mobile fraction of the molecule can be assigned. Cross‐polarization magic‐angle spinning (CPMAS) permits the evaluation of changes in the NMR line shapes and chemical shifts. The employment of proton spin‐lattice relaxation times (T1 and T1ρ) gives useful information on the molecular dynamic in heterogeneous polymers. From these parameters the response of the molecular mobility behavior of the polymer chains can be obtained. The results of the present work are discussed in this article in terms of molecular mobility and domain formations of heterogeneous amorphous polymers in order to understand the relations in the structure–mobility property. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 473–476, 2003
Guidelines for dryer design based on results from non‐Fickian model
Authors: Vinjamur Madhu , Cairncross Richard A.
Published: November 2002

In polymer solution coatings below the glass transition temperature of the pure polymer, the coating can go undergo a glass transition and develop stresses during drying. When stresses develop, a non‐Fickian model accurately describes solvent mass transport in drying polymer coatings. The non‐Fickian model includes the solvent transport due to both stress and concentration gradients. This article presents a non‐Fickian model, which predicts a lower residual solvent than does the corresponding Fickian model. We showed in an earlier article that the non‐Fickian model predicts trapping skinning (higher residual solvent under more intense operating conditions) at higher drying gas‐flow rates. In this article, the non‐Fickian model was used to investigate how the gas‐flow rate, dry film thickness, and substrate thickness affect the residual solvent for a single‐zone dryer. This work recommends guidelines for choosing gas‐flow rates, gas temperatures, and substrate thickness to minimize the residual solvent. The model predictions show that, at any gas temperature, the residual solvent is minimum at an intermediate gas‐flow rate. The trapping skinning effect is less evident in thicker coatings and substrates. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 477–486, 2003
Influence of mixing cycle on the degree of mixing of calcite‐filled polyethylene upon stretching
Authors: Kim Kwang‐Jea , Kwon Sangmin , Kim Hyun , Kundu Patit P. , Kim Yong‐Wook , Lee Yong‐Keun , Lee Kyu Jong , Lee Byung H. , Choe Soonja
Published: November 2002

The mixing cycle‐dependent degree of dispersion and degree of mixing of a calcite (calcium carbonate) agglomerate in high‐density polyethylene (HDPE), low‐density polyethylene (LDPE), and linear low‐density polyethylene (LLDPE) matrices upon stretching was investigated using three different techniques: mechanical property, morphological behavior, and image analyzer analyses. The mechanical properties analyzed in terms of the tensile strength and maximum elongation resulted in that the second mixing was the best for giving a better property for all systems except the LDPE system, which exhibited no significant difference between the second and third mixings. The morphological behavior of the three compounds were different, but no distinctive difference was observed to differentiate the degree of mixing from system to system. The number‐, weight‐, and z + 1‐average diameters of the air hole and the aspect ratio upon the stretching and mixing cycle were calculated to analyze the degree of mixing of the calcite‐filled composites. As a consequence, no difference in the average diameter of the air hole was obtained among the three systems, but the aspect ratios of the air hole varied significantly. Thus, the degree of dispersion and the degree of mixing may be influenced by the average calcite agglomerate size, the average diameter of the air hole, and the aspect ratio upon stretching and mixing cycles. Those factors would be formed by the difference in chemical characteristics upon various microstructures of polyethylene and its molecular weight and molecular weight distribution. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 311–321, 2003
Comparative study of maleated polyolefins as compatibilizers for polyethylene/wood flour composites
Authors: Lai Sun‐M. , Yeh Feng‐C. , Wang Yeh , Chan Hsun‐C. , Shen Hsiao‐F.
Published: November 2002

The effects of various types of compatibilizers on the mechanical properties of high‐density polyethylene/wood flour composites were investigated. Functionalized polyolefins, including maleated polyethylenes, polypropylene, and styrene–ethylene/butylene–styrene copolymer, were incorporated to reduce the interfacial tension between the polyethylene matrix and wood filler. Of these, maleated linear low‐density and high‐density polyethylenes gave higher tensile and impact strengths for the composites, presumably because of their better compatibility with the high‐density polyethylene matrix. Similar but less enhanced improvements in the mechanical properties, depending on the compatibilizer loading, were seen for a maleated styrene–ethylene/butylene–styrene triblock copolymer, whereas maleated polypropylene only slightly improved the tensile modulus and tensile strength, which increased with increasing compatibilizer loadings. Scanning electron microscopy was used to reveal the interfacial region and confirm these findings. Dynamic mechanical thermal measurements showed the interaction between the filler and the matrix. Fourier transform infrared spectroscopy was used to assign the chemical fixation and the various chemical species involved on the surfaces of the fillers before and after surface treatment. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 487–496, 2003
Atomic force microscopy studies of admicellar polymerization polystyrene‐modified amorphous silica
Authors: See Chun Hwa , O'Haver John
Published: November 2002

Atomic force microscopy was used to study polystyrene‐modified silica surfaces produced by admicellar polymerization (polymerization of monomers solubilized in adsorbed surfactant aggregates). The goal was to examine changes in the location and nature of the formed polystyrene resulting from changes in the surfactant and monomer feed levels on precipitated silica. Normal tapping and phase‐contrast modes in air were used to image the topography of the polystyrene‐modified silica. Moderate‐to‐light force‐tapping mode was used to differentiate between the silica surface and adsorbed water or polymer. The formed polystyrene exists primarily in the pores, with patches extending onto the exposed surface of the silica particles. At moderate tapping forces, darker phase regions were observed in the valleys and pores of the silica in both the modified and the unmodified samples. Upon higher magnification, the darker regions disappear on unmodified silicas, whereas polymer bands become evident on the modified silicas. At lower loadings of surfactant and monomer, the number and extent of polymer patches decreased, with polymer being found only in pores. The polystyrene patches observed inside the valleys of the amorphous silica varied from 1 to 10 nm in thickness. The structure of the polystyrene film formed on precipitated silica was found to be insensitive to the surfactant feed concentration. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 290–299, 2003
Blends of aliphatic polyesters. VIII. Effects of poly(L‐lactide‐co‐ε‐caprolactone) on enzymatic hydrolysis of poly(L‐lactide), poly(ε‐caprolactone), and their blend films
Authors: Tsuji Hideto , Yamada Tamami
Published: November 2002

Poly(L‐lactide), that is, poly(L‐lactic acid) (PLLA), poly(ε‐caprolactone) (PCL), and their blend (50/50) films containing different amounts of poly(L‐lactide‐co‐ε‐caprolactone) (PLLA‐CL), were prepared by solution casting. The effects of added PLLA‐CL on the enzymatic hydrolysis of the films were investigated in the presence of proteinase K and Rhizopus arrhizus lipase by use of gravimetry. The addition of PLLA‐CL decreased the proteinase K–catalyzed hydrolyzabilities of the PLLA and PLLA/PCL (50/50) films as well as the Rhizopus arrhizus lipase‐catalyzed hydrolyzability of the PCL and PLLA/PCL (50/50) films. The decreased enzymatic hydrolyzabilities of the PLLA and PCL films upon addition of PLLA‐CL are attributable to the fact that the PLLA‐CL is miscible with PLLA and PCL and the dissolved PLLA‐CL must disturb the adsorption and/or scission processes of the enzymes. In addition to this effect, the decreased enzymatic hydrolyzabilities of the PLLA/PCL (50/50) films upon addition of PLLA‐CL can be explained by the enhanced compatibility between the PLLA‐rich and PCL‐rich phases arising from the dissolved PLLA‐CL. These effects result in decreased hydrolyzable interfacial area for PLLA/PCL films. The decrement in proteinase K–catalyzed hydrolyzability of the PLLA film upon addition of PLLA‐CL, which is miscible with PLLA, was in marked contrast with the enhanced proteinase K–catalyzed hydrolyzability of the PLLA film upon addition of PCL, which is immiscible with PLLA. This confirms that the miscibility of the second polymer is crucial to determine the proteinase K–catalyzed hydrolyzabilities of the PLLA‐based blend films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 412–419, 2003
Monodisperse polymer/metal composite particles by electroless chemical deposition: Effect of surface functionality of polymer particles
Authors: Park Jin‐Gyu , Kim Jin‐Woong , Oh Seong‐Geun , Suh Kyung‐Do
Published: November 2002

Micron‐sized polymer particles were coated with layers of nickel compounds by plating electrolessly in the presence of aqueous solutions of nickel chloride, sodium hypophosphite, sodium citrate, and ammonium chloride at elevated temperature. The uniform functional polymer particle could be obtained by seeded polymerization. To investigate the effect of surface functionality on the conditions for nickel deposition, the polymer particle was functionalized with the thiol group. From morphological observation, it was found that the mode of nickel deposition was greatly dependent on the surface functionality of the polymer particle. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 420–424, 2003
Effect of the casting solvent on the free‐volume characteristics and gas permeability of poly[1‐(trimethylsilyl)‐1‐propyne] membranes
Authors: Bi Jing Jing , Wang C. L. , Kobayashi Y. , Ogasawara K. , Yamasaki A.
Published: November 2002

The effect of the casting solvent on the structure of poly[1‐(trimethylsilyl)‐1‐propyne] (PTMSP) membranes was investigated experimentally. The PTMSP membranes were cast from solutions of cyclohexane, toluene, and tetrahydrofuran; the membranes were characterized by the positron annihilation lifetime spectroscopy (PALS) technique and by gas‐permeation measurements of O2, N2, and CO2. The decay curves from the positron annihilation lifetime spectroscopy gave the best fit when two long‐life components (τ3 and τ4, τ3 < τ4) were employed. This suggests that two types of free volume existed in the PTMSP membranes. The size and number density of τ4, which was characteristic for PTMSP, decreased in the following order of the casting solvents: cyclohexane > toluene > tetrahydrofuran. The order was consistent with the order of gas permeability. A good correlation was observed between the permeability and the structural parameter that denoted the free‐volume size and the number density of τ4. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 497–501, 2003
Poly(3‐chlorothiophene) films prepared by the direct electrochemical oxidation of 3‐chlorothiophene in mixed electrolytes of boron trifluoride diethyl etherate and sulfuric acid
Authors: Xu Jingkun , Shi Gaoquan , Chen Fengen , Wang Fan , Zhang Jiaxin , Hong Xiaoyin
Published: November 2002

3‐Chlorothiophene (CT) was electrochemically polymerized in mixed electrolytes of a boron trifluoride diethyl etherate solution containing 0–20% (by volume) sulfuric acid. The oxidation potentials of the monomer in these media were measured to be only 1.06–1.31 V (vs Ag/AgCl). These values were much lower than that of CT in acetonitrile and 0.1 mol/L (Bu)4NBF4 (1.92 V vs Ag/AgCl). Poly(3‐chlorothiophene) (PCT) films with conductivities of 0.1–2 S cm−1 were obtained. The structure, morphology, and electrochemical behavior of the PCT films also were investigated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 502–509, 2003
Preparation and properties of poly(ethylene oxide) star polymers
Authors: Peppas Nicholas A. , Argade Ankush , Bhargava Saumitra
Published: November 2002

Poly(ethylene oxide) (PEO) star polymers were prepared by anionic polymerization of methacryloyl chloride and glyceryl trimethacrylate with sec‐butyllithium in cyclohexane. The ensuing polymers were grafted with poly(ethylene glycol) of molecular weight 400. The final product was washed with methylene chloride and analyzed with infrared spectroscopy, differential scanning calorimetry, and thermogravimetry. Star polymers of PEO were also prepared by anionic polymerization of glycidol with sec‐butyllithium in cyclohexane. The initiator was chosen so as to yield a polymer of 10,000 molecular weight. The resulting polymers were analyzed by nuclear magnetic resonance, infrared spectroscopy, and thermogravimetry. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 322–327, 2003
Graft copolymer–lanthanide complexes obtained by radiation grafting on polyethylene film
Authors: Choi Seong‐Ho , Lee Kwang‐Pill , Sohn Sang‐Ho
Published: November 2002

Radiation‐induced grafting of acrylic acid (AAc) onto polyethylene (PE) film was investigated. The grafted films rapidly adsorbed Eu, Gd, Tb, and Dy ions at high efficiency. The carboxylic acid groups on the AAc‐grafted PE film acted as a chelating site for the selected lanthanide ions. Complex formation of lanthanide ions and the carboxylic acid group on PE film was investigated by IR, FT–Raman, and X‐ray photoelectron spectroscopy (XPS). Photoluminescence (PL) spectra and the thermal properties of the graft copolymer–lanthanide complexes onto PE film were also investigated. The application of such prepared graft copolymer–lanthanide complexes in the field of fluorescence emission displays (FEDs) may be interest. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 328–336, 2003
Preparation and characteristics of composites of high‐crystalline cellulose with polypropylene: Effects of maleated polypropylene and cellulose content
Authors: Qiu Wulin , Zhang Farao , Endo Takashi , Hirotsu Takahiro
Published: November 2002

Binary composites of high‐crystalline fibrous cellulose with polypropylene (PP) or maleic anhydride‐grafted polypropylene (MAPP) were prepared by melt‐mixing with different contents of cellulose from 0 to 60 wt %. Ternary composites of cellulose with PP and MAPP were also prepared to investigate the effects of MAPP as a compatibilizer between cellulose and PP. Scanning electron microscopy revealed that the addition of MAPP generates strong interactions between a PP matrix and cellulose fibers: All cellulose fibers are encapsulated by layers of the matrix and connected tightly within the matrix. Thus, the tensile strength and Young's modulus of MAPP‐containing composites increase with an increase in MAPP and cellulose content, in contrast to the decrease in tensile strength of a PP‐based binary composite with an increase in cellulose. Cellulose fibers act as a nucleating agent for the crystallization of PP, which is promoted by the addition of MAPP through an increase of the crystallization temperature of PP in the composite. Accordingly, both cellulose and MAPP facilitate the thermooxidative stability of PP composites in the following order: MAPP/cellulose > PP/MAPP/cellulose > PP/cellulose > PP. Relative water absorption increases with an increase in cellulose content, decreasing with the addition of MAPP. MAPP‐containing cellulose composites have high potential for applications as environmentally friendly materials. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 337–345, 2003
Blends of i‐PP and SBS. II. Influence of in situ compatibilization on the mechanical properties
Authors: Wilhelm Helena Maria , Felisberti Maria Isabel
Published: November 2002

This article concerns the in situ compatibilization of immiscible isotatic polypropylene/styrene–butadiene–styrene triblock copolymer blends (i‐PP/SBS) by use of a reactive mixture. For this purpose, maleated PP (PP–MAH) and SBS (SBS–MAH) were used as functionalized polymers and 4,4′‐diaminediphenylmethane was used as a coupling agent between maleated polymers, resulting in a graft copolymer. Binary blends of i‐PP/SBS, nonreactive ternary blends of i‐PP/PP–MAH/SBS, and reactive ternary blends of i‐PP/PP–MAH/SBS–MAH with varying diamine/anhydride molar ratios were prepared. The mechanical properties of the blends were determined by tensile and impact‐resistance tests. The optimum improvement in the mechanical properties was found when the diamine/anhydride molar ratio in the ternary reactive blends was 0.5/1. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 516–522, 2003
Investigation of plasma polymerized benzene and furan thin films for application in opto‐electronic devices
Authors: Jobanputra Manish C. , Durstock Michael F. , Clarson Stephen J.
Published: November 2002

Conjugated polymers are among the most promising organic materials for opto‐electronic devices. In such applications, the main fabrication problem is to get uniform, defect‐free, and reproducible thin films of these materials. In this investigation, an RF plasma reactor was used to produce cross‐linked organic thin films from benzene and furan precursors. Uniform thin films of desired thickness were fabricated using this plasma polymerization technique. The composition of the plasma‐polymerized films was determined with X‐ray photoelectron spectroscopy. Fourier transform infrared spectra of the monomers and plasma‐polymerized thin films prepared were compared to analyze the chemical structure of the films. Ultraviolet–visible absorption spectroscopy shows a red shift of 45 nm in λmax for the case of plasma‐polymerized benzene films and 52 nm in the case of plasma‐polymerized furan films when compared to their respective monomer spectra. Photo luminescence spectra of these films show a blue emission with a broad peak at 460 nm for the plasma‐polymerized benzene films and 445 nm for the plasma‐polymerized furan films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 523–528, 2003
Environmental stress cracking of poly(butylene succinate)/cellulose triacetate blend films
Authors: Tatsushima Tohru , Ogata Nobuo , Nakane Koji , Ogihara Takashi
Published: November 2002

Blend films of poly(butylene succinate) (PBS) with cellulose triacetate (CTA) were prepared using a solvent‐cast technique. The environmental stress cracking (ESC) behavior of commercial PBS films and that of as‐prepared PBS/CTA blend films were investigated in an aqueous NaOH solution. It was found that the fracture behavior of PBS films can be analyzed by linear fracture mechanics, that is, the stress‐intensity factor, K, is found to control the crack‐growth rate, da/dt, in PBS films. The enhancement of da/dt induced by increasing the normality of NaOH(aq) is more marked at a high value of K rather than at a low value of K. Furthermore, the ESC behavior of the PBS/CTA blends was studied in NaOH(aq). It was found that the behavior cannot be analyzed by linear fracture mechanics and that the addition of CTA into PBS increases the ESC resistance of the blends. Large‐scale yielding of the material around the crack tip seems to be responsible for the high ESC resistance of the blends. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 510–515, 2003
Graft copolymerization of methyl acrylate onto poly(vinyl alcohol) initiated by potassium diperiodatonickelate(IV)
Authors: Liu Yinghai , Liu Xiaohui , Deng Kuilin , Liu Zhanjun
Published: November 2002

The graft copolymerization of methyl acrylate onto poly(vinyl alcohol) (PVA) with a potassium diperiodatonickelate(IV) [Ni(IV)]–PVA redox system as an initiator was investigated in an alkaline medium. The grafting parameters were determined as functions of the temperature and the concentrations of the monomer and initiator. The structures of the graft copolymers were confirmed by Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. The Ni(IV)–PVA system was found to be an efficient redox initiator for this graft copolymerization. A single‐electron‐transfer mechanism was proposed for the formation of radicals and the initiation. Other acrylate monomers, such as methyl methacrylate, ethyl acrylate, n‐butyl acrylate, and n‐butyl methacrylate, were used as reductants for graft copolymerization. These reactions definitely occurred to some degree. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 529–534, 2003
Electroactive mixtures of polyaniline and EPDM rubber: Chemical, thermal, and morphological characterization
Authors: Domenech S. C. , Bortoluzzi J. H. , Soldi V. , Franco C. V.
Published: November 2002

A new route for blending polyaniline (PAni) and EPDM rubber was devised with maleic anhydride as a compatibilizer precursor. Rubber matrices containing ammonium peroxidisulfate and dodecyl benzene sulfonic acid were cast from organic solvents. Exposure to the monomer vapors allowed the chemical polymerization of aniline. The influence of PAni and the compatibilizer on the thermal properties, chemical structure, electrical conductivity, and morphology of the mixtures was observed with differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared, in situ conductivity measurements, and optical microscopy. The micrographs showed a good distribution of the PAni complex in the matrix. The use of approximately 2 wt % compatibilizer resulted in chemical interactions between maleic anhydride and the PAni complex formed with dodecyl benzene sulfonic acid, which could enhance the compatibility between the polymers. The obtained blends reached relative electrical conductivity values of up to 9 × 10−3 S cm−1. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 535–547, 2003
Molar group contributions to polymer flammability
Authors: Walters Richard N. , Lyon Richard E.
Published: November 2002

The specific heat‐release rate is the molecular‐level fire response of a burning polymer. The Federal Aviation Administration obtains the specific heat‐release rate of milligram samples by analyzing the oxygen consumed by the complete combustion of the pyrolysis gases during a linear heating program. Dividing the specific heat‐release rate (W/g) by the rate of the temperature rise (K/s) of a sample during a test gives a material fire parameter with the units (J/g K) and significance of the heat (release) capacity. The heat‐release capacity appears to be a true material property that is rooted in the chemical structure of the polymer and is calculable from additive molar group contributions. Hundreds of polymers of known chemical compositions have been tested to date, providing over 40 different empirical molar group contributions to the heat‐release capacity. Measured and calculated heat‐release capacities for over 80 polymers agree to within ±15%, suggesting a new capability for predicting flammability from the polymer chemical structure. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 548–563, 2003
Compatibilization of syndiotactic polystyrene and a thermotropic liquid‐crystalline polymer blend with a zinc salt of a sulfonated polystyrene ionomer
Authors: Son Younggon , Weiss R. A.
Published: November 2002

A zinc salt of a lightly sulfonated (4.5 mol %) polystyrene ionomer was used to compatibilize a 3/1 (w/w) blend of syndiotactic polystyrene and a wholly aromatic thermotropic liquid‐crystalline polymer (TLCP). The addition of the ionomer significantly reduced the dispersed TLCP domain size and improved the tensile strength, ultimate elongation, and flexural toughness of the blend. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 564–568, 2003
Effect of the physicochemical properties on the permeation performance in fully aromatic crosslinked polyamide thin films
Authors: Juhn Roh Il
Published: November 2002

Thin‐film‐composite reverse‐osmosis (RO) membranes were prepared by the interfacial polymerization of trifunctional 1,3,5‐benzentricarbonyl chloride (TMC) with difunctional 1,3‐benzendiamine (MPDA) or 1,4‐benzendiamine (PPDA). The meta‐positioned polyamide (MPDA/TMC) resulted in higher water flux but lower salt rejection than the para‐positioned polyamide (PPDA/TMC). To understand this behavior, we studied various factors including the thickness, rupture strength, chemical properties, and solubilities of the water and salt in the thin‐film polyamide. The thin films made from MPDA and PPDA possessed similar thicknesses and rupture strengths adequate for withstanding the RO operation pressure. However, the meta‐positioned polyamide had higher hydrophilicity and greater molecular chain mobility than the para‐positioned polyamide, resulting in higher water flux. In contrast, the para‐positioned polyamide had lower salt solubility and lower molecular chain mobility than the meta‐positioned polyamide, thereby possessing higher salt rejection. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 569–576, 2003
Molecular dynamics simulation studies of induced fit and conformational capture in U1A–RNA binding: Do molecular substates code for specificity?
Authors: Pitici Felicia , Beveridge David L. , Baranger Anne M.
Published: November 2002

Molecular dynamics (MD) simulations on stem loop 2 of U1 small nuclear RNA and a construct of the U1A protein were carried out to obtain predictions of the structures for the unbound forms in solution and to elucidate dynamical aspects of induced fit upon binding. A crystal structure of the complex between the U1A protein and stem loop 2 RNA and an NMR structure for the uncomplexed form of the U1A protein are available from Oubridge et al. (Nature, 1994, Vol. 372, pp. 432–438) and Avis et al. (Journal of Molecular Biology, 1996, Vol. 257, pp. 398–411), respectively. As a consequence, U1A–RNA binding is a particularly attractive case for investigations of induced fit in protein–nucleic acid complexation. When combined with the available structural data, the results from simulations indicate that structural adaptation of U1A protein and RNA define distinct mechanisms for induced fit. For the protein, the calculations indicate that induced fit upon binding involves a non‐native thermodynamic substate in which the structure is preorganized for binding. In contrast, induced fit of the RNA involves a distortion of the native structure in solution to an unstable form. However, the RNA solution structures predicted from simulation show evidence that structures in which groups of bases are favorably oriented for binding the U1A protein are thermally accessible. These results, which quantify with computational modeling recent proposals on induced fit and conformational capture by Leuillot and Varani (Biochemistry, 2001, Vol. 40, pp. 7947–7956) and by Williamson (Nature Structural Biology, 2000, Vol. 7, pp. 834–837) suggest an important role for intrinsic molecular architecture and substates other than the native form in the specificity of protein–RNA interactions. © 2002 Wiley Periodicals, Inc. Biopolymers 65: 424–435, 2002
Stability of protein‐bound conformations of bioactive peptides: The folded conformation of an epidermal growth factor‐like thrombomodulin fragment is similar to that recognized by thrombin
Authors: Song Jianxing , Xu Ping , Koutychenko Anatol , Ni Feng
Published: November 2002

The relationship between the free and bound conformations of bioactive peptides is explored using the epidermal growth factor (EGF)‐like thrombomodulin fragment hTM409–426 as a model system. The hTM409–426 peptide has a sequence of C409PEGYILDDGFIC421TDIDE (with a disulfide bond between Cys409 and Cys421) and is a selective inhibitor of thrombin. Upon binding to thrombin, hTM409–426 adopts a well‐defined conformation—namely, a β‐turn followed by an antiparallel β‐sheet, similar to those found in all other EGF‐like protein repeats (Hrabal et al., Protein Science, 1996, Vol. 5, 195–203). Here we demonstrate that, at pH 6.8 and at 25°C, the hTM409–426 peptide in the free state is very flexible, but still populates a type II β‐turn over residues Pro410–Glu411–Gly412–Tyr413 and the clustering of some hydrophobic side chains, both of which are present in the thrombin‐bound conformation. At a lower temperature of 5 °C, significant conformational shifts of the CαH proton resonances and extensive medium‐ and long‐range NOEs are observed, indicating the presence of folded conformations with unique backbone–backbone and side‐chain interactions. A comparison of the NOE patterns in the free state with transferred NOEs shows that the free‐state folded and the thrombin‐bound conformations of the hTM409–426 peptide are very similar, particularly over residues Pro410–Ile424. The folded conformation of hTM409–426 appears to be stabilized by two hydrophobic clusters, one formed by the side chains of residues Pro410, Tyr413, Leu415, and Phe419 and the Cys409–Cys421 disulfide bond, the second involving residues Ile414 and Ile424. These results indicate that the overall topology of the thrombin‐bound conformation of the hTM409–426 peptide is prefolded in the free state and the primary sequence (including the disulfide bond) may be selective for an ensemble of conformations similar to that recognized by thrombin. Published 2002 Wiley Periodicals, Inc. Biopolymers 65: 373–386, 2002
Probing multiple effects on 15N, 13Cα, 13Cβ, and 13C′ chemical shifts in peptides using density functional theory
Authors: Xu Xiao‐Ping , Case David A.
Published: November 2002

We have used density functional calculations on model peptides to study conformational effects on 15N, 13Cα, 13Cβ, and 13C′ chemical shifts, associated with hydrogen bonding, backbone conformation, and side‐chain orientation. The results show a significant dependence on the backbone torsion angles of the nearest three residues. Contributions to 15N chemical shifts from hydrogen bonding (up to 8 ppm), backbone conformation (up to 13 ppm), side‐chain orientation and neighborhood residue effects (up to 22 ppm) are significant, and a unified theory will be required to account for their behavior in proteins. In contrast to this, the dependence on sequence and hydrogen bonding is much less for 13Cα and 13Cβ chemical shifts (<0.5 ppm), and moderate for carbonyl carbon shifts (<2 ppm). The effects of side‐chain orientation are mainly limited to the residue itself for both nitrogen and carbon, but the χ1 effect is also significant for the nitrogen shift of the following residue and for the 13C′ shift of the preceding residue. The calculated results are used, in conjunction with an additive model of chemical shift contributions, to create an algorithm for prediction of 15N and 13C shifts in proteins from their structure; this includes a model to extrapolate results to regions of torsion angle space that have not been explicitly studied by density functional theory (DFT) calculations. Crystal structures of 20 proteins with measured shifts have been used to test the prediction scheme. Root mean square deviations between calculated and experimental shifts 2.71, 1.22, 1.31, and 1.28 ppm for N, Cα, Cβ, and C′, respectively. This prediction algorithm should be helpful in NMR assignment, crystal and solution structure comparison, and structure refinement. © 2002 Wiley Periodicals, Inc. Biopolymers 65: 408–423, 2002
Chain stiffness of heteropolysaccharide from Aeromonas gum in dilute solution by dynamic light scattering
Authors: Xu Xiaojuan , Zhang Lina , Nakamura Yo , Norisuye Takashi
Published: November 2002

Dynamic light scattering measurements have been made on 15 fractions of aeromonas (A) gum, an extracellular heteropolysaccharide produced by the strain Aeromonas nichidenii, with dimethylsulfoxide containing 0.2M lithium chloride as the solvent at 25°C. Data for the translational diffusion coefficient D covering a molecular weight range from 4.5 × 105 to 2.1 × 106 and ratios of the z‐average radius of gyration 〈s2〉z1/2 to the hydrodynamic radius RH (calculated with previous 〈s2〉z data) suggest that the polymer behaves like a semiflexible chain in this solvent similar to the stiffness of cellulose derivatives. Thus the D data are analyzed on the basis of the Yamakawa–Fujii theory for the translational friction coefficient of a wormlike cylinder by coarse‐graining the heteropolysaccharide molecule. Excluded‐volume effects are taken into account in the quasi‐two‐parameter scheme, as was done previously for 〈s2〉z and [η] (the intrinsic viscosity) of A gum in the same solvent. The molecular weight dependence of RH is found to be explained by the perturbed wormlike chain with a persistence length of 10 nm, a linear mass density of 1350 nm−1, an excluded‐volume strength parameter of 1.3 nm, and a chain diameter of 2.8 nm. These parameters are in substantial agreement with those estimated previously from 〈s2〉z and [η] data, demonstrating that the solution properties (D, 〈s2〉z, and [η]) of the heteropolysaccharide are almost quantitatively described by the current theories for wormlike chains in the molecular weight range studied. © 2002 Wiley Periodicals, Inc. Biopolymers 65: 387–394, 2002
Molecular structure of the outer bacterial membrane of Pseudomonas aeruginosa via classical simulation
Authors: Shroll Robert M. , Straatsma T. P.
Published: November 2002

A detailed structural analysis has been performed of the outer bacterial membrane of Pseudomonas aeruginosa using a parameterized classical simulation model (R. D. Lins and T. P. Straatsma, Biophysical Journal, 2001, Vol. 81, pp. 1037–1046) with modest modifications. The structural analysis of the membrane is presented and newly discovered characteristics of the membrane are discussed. Simulations indicate that the relative contribution of different ligands to calcium ion coordination varies across the membrane, while maintaining a constant average coordination number of 6.1. Water penetrates the surface of the membrane to a depth of about 30 Å. The hydration of ions and phosphate groups is shown to depend on location within the membrane. A measure of saccharide residue orientation is defined and average orientations are presented. Saccharide residues possess varying degrees of motion with a trend of greater mobility at the membrane surface. However, their motion is limited and even in the membrane outer core region the average structure appears fairly rigid over a period of 1 ns. © 2002 Wiley Periodicals, Inc. Biopolymers 65: 395–407, 2002
Initial treatment for prostate carcinoma in relation to comorbidity and symptoms
Authors: Hall H. Irene , Satariano William A. , Thompson Trevor , Ragland Kathleen E. , Van Den Eeden Stephen K. , Selvin Steve
Published: November 2002

BACKGROUND

Evidence suggests the type of treatment received for prostate carcinoma is associated with comorbidity, but little information is available on associations with specific comorbid disease or symptoms. The authors examined the relations between treatment and comorbidity, specific comorbid disease, and symptoms.

METHODS

Medical records were abstracted for 1054 male members of the Kaiser Permanente medical care program diagnosed with prostate carcinoma from 1975 to 1987. Information was obtained on demographic characteristics, comorbid conditions, symptoms, tumor stage and grade, and treatment. Logistic regression was used to determine the significant predictors of treatment (radiation vs. nonaggressive treatment and surgery vs. nonaggressive treatment).

RESULTS

Compared to nonaggressive treatment, radiation treatment was less likely among men who had prior cancer (adjusted odds ratio [OR] 0.29, 95% confidence interval [CI] 0.09–0.90) or cerebrovascular disease (OR 0.33, 95% CI 0.13–0.83). There was a significant interaction between race and myocardial infarction (P = 0.02). Surgery, compared to nonaggressive treatment, was less common among men with a prior cancer (OR 0.21, 95% CI 0.07–0.63) or congestive heart failure (OR 0.29, 95% CI 0.09–0.90). Significant interactions were observed between race and myocardial infarction (P = 0.01), diabetes and dysuria or hematuria (P = 0.02), and para‐ or hemiplegia and urinary frequency or nocturia (P = 0.01).

CONCLUSIONS

Specific symptoms and comorbidity appear to influence treatment for prostate carcinoma. More research is needed on treatment differences by race. Cancer 2002;95:2308–15. Published 2002 by the American Cancer Society.

DOI 10.1002/cncr.10926
Pathologic review of the Mayo Lung Project
Authors: Colby Thomas V. , Tazelaar Henry D. , Travis William D. , Bergstralh Erik J. , Jett James R.
Published: November 2002

BACKGROUND

In the Mayo Lung Project Screening Trial, there were more carcinomas identified in the screened group compared with the control group. The screened group had better survival, but there was no difference in lung carcinoma mortality between the screened group and the control group. The purpose of this study was to review all available original pathology from the trial to determine whether overdiagnosis (carcinomas that do not result in the death of the patient) or misdiagnosis of lung carcinoma may explain this discrepancy.

METHODS

All available lung pathology slides from patients who underwent surgery at the Mayo Clinic were reviewed independently by three blinded lung pathologists. Tumors were classified according to the 1999 World Health Organization criteria. In addition, agreement among the pathologists was assessed.

RESULTS

Among 106 patients who underwent surgery at the Mayo Clinic, slides were available for review from 105 patients, including 77 slides from the screened group and 28 slides from the control group. The original diagnosis of carcinoma was confirmed in all patients. In 7 patients (6.7%), there was unanimous agreement that the lesion was preinvasive (carcinoma in situ), and these lesions all were from the screened group. In 90 patients (85.5%), there was unanimous agreement that the tumors were invasive. In 8 patients (7.8%), there was some disagreement between the observers about whether lesions were invasive or preinvasive; 7 of these 8 lesions were from the screened group. The level of agreement among pathologists for invasive carcinomas was > 94% for all comparisons, and the κ statistic ranged from 0.67 (substantial agreement) to 0.84 (almost perfect agreement). There was good agreement among the pathologists about tumor cell type with the κ statistic ≥ 0.65.

CONCLUSIONS

The histologic diagnosis of carcinoma was confirmed for all 105 slides that were reviewed. The results of this study indicate that misdiagnosis does not explain the increased numbers of carcinomas identified in the screened group. The increased numbers of in situ carcinomas in the screened group resulted in increased numbers of squamous carcinomas in the screened group compared with the control group and may have contributed to the better survival. It is possible that carcinoma in situ accounted for some instances of overdiagnosis. Cancer 2002;95:2361–5. © 2002 American Cancer Society.

DOI 10.1002/cncr.10930