bluuebunny/crossref_metadata_2025 huggingface dataset:
Main kinetic features of ethylene polymerization reactions with heterogeneous Ziegler–Natta catalysts in the light of a multicenter reaction mechanism
Authors: Kissin Yury V.
Published: October 2004

A previously developed kinetic scheme for ethylene polymerization reactions with heterogeneous Ziegler–Natta catalysts (see Y. V. Kissin, R. I. Mink, & T. E. Nowlin, J Polym Sci Part A: Polym Chem 1999, 37, 4255 and Y. V. Kissin, R. I. Mink, T. E. Nowlin, & A. J. Brandolini, J Polym Sci Part A: Polym Chem 1999, 37, 4273, 4281) states that the catalysts have several types of active centers that have different activities and different stabilities, produce different types of polymer materials, and respond differently to reaction conditions. Each type of center produces a single polymer component (Flory component), a material with a uniform structure (copolymer composition, isotacticity, etc.) and a narrow molecular weight distribution (weight‐average molecular weight/number‐average molecular weight = 2.0). This article examines several previously known features of ethylene polymerization and copolymerization reactions on the basis of this mechanism. The discussed subjects include temperature and cocatalyst effects on the polymerization kinetics and molecular weight distribution of polymers and reaction parameter effects (temperature, ethylene and hydrogen partial pressures, and α‐olefin and cocatalyst concentrations) on the molecular weights of Flory components. The results show that the formulation of the multicenter kinetic scheme and the development of kinetic tools necessary for the application of this scheme significantly expand our understanding of the working of heterogeneous polymerization catalysts and provide additional means for their control. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1681–1695, 2001
Photoinitiated polymerization of methacrylic monomers in a polystyrene matrix: Kinetic, mechanistic, and structural aspects
Authors: Mateo J. L. , Calvo M. , Bosch P.
Published: October 2004

The kinetics and mechanism of the photoinitiated polymerization of tetrafunctional and difunctional methacrylic monomers [1,6‐hexanediol dimethacrylate (HDDMA) and 2‐ethylhexyl methacrylate (EHMA)] in a polystyrene (PS) matrix were studied. The aggregation state, vitreous or rubbery, of the monomer/matrix system and the intermolecular strength of attraction in the monomer/matrix and growing macroradical/matrix systems are the principal factors influencing the kinetics and mechanism. For the PS/HDDMA system, where a relatively high intermolecular force of attraction between monomer and matrix and between growing macroradical and matrix occurs, a reaction‐diffusion mechanism takes place at low monomer concentrations (<30–40%) from the beginning of the polymerization. For the PS/EHMA system, which presents low intermolecular attraction between monomer and matrix and between growing macroradical and matrix, the reaction‐diffusion termination is not clear, and a combination of reaction‐diffusion and diffusion‐controlled mechanisms explains better the polymerization for monomer concentrations below 30–40%. For both systems, for which a change from a vitreous state to a rubbery state occurs when the monomer concentration changes from 10 to 20%, the intrinsic reactivity and kp/kt1/2 ratio (where kp is the propagation kinetic constant and kt is the termination kinetic constant) increase as a result of a greater mobility of the monomer in the matrix (a greater kp value). The PS matrix participates in the polymerization process through the formation of benzylic radical, which is bonded to some extent by radical–radical coupling with the growing methacrylic radica, producing grafting on the PS matrix. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2049–2057, 2001
“Charge transfer” polymerization—and the absence thereof!
Authors: Hall, H. K. , Padias Anne Buyle
Published: October 2004

Mechanisms for “charge‐transfer” spontaneous polymerizations and cycloadditions between electron‐rich olefins and electron‐poor olefins were reviewed. As for propagation, literature proposals involving charge‐transfer complexes were rejected. Instead, alternating copolymerization is ascribed to polar effects in free‐radical reactions. As for spontaneous initiation, literature proposals involving charge‐transfer complexes, with or without proton transfer, were rejected. Instead, the initiating species is postulated to be a tetramethylene zwitterion biradical, which may initiate either ionic homopolymerization or free‐radical copolymerization. A new hypothesis proposes that any interaction that brings vinyl monomers close together may facilitate tetramethylene formation and spontaneous polymerization. These interactions include Coulombic, acid–base, hydrophobic–hydrophilic and templating–tethering interactions. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2069–2077, 2001
Modified polysulfones. IV. Synthesis and characterization of polymers with silicon substituents for a comparative study of gas‐transport properties
Authors: Guiver Michael D. , Robertson Gilles P. , Rowe Sheri , Foley Stephen , Kang Yong Soo , Park Hyun Chae , Won Jongok , Thi Hoai Nam Le
Published: October 2004

We previously conducted a detailed study of gas‐transport and other properties of a series of silicon derivatives of Udel polysulfone (PSf) and Radel polyphenylsulfone; we now report the details of their preparation by the reaction of lithiated polymer intermediates with chlorosilylalkylaryl electrophiles. Ortho‐sulfone‐substituted polymers with pendant trimethylsilyl, dimethylphenylsilyl, and diphenylmethylsilyl and other groups were obtained by direct metalation followed by the reaction of the dilithiated intermediate with the appropriate silyl electrophile. In addition, the structural regularity and geometry of the dilithiated site was also exploited to introduce silicon into the main chain by the reaction of dichlorosilyl electrophiles, leading to the formation of a new tricyclic heteroatom ring. Ortho‐ether PSf derivatives were obtained from a dibrominated polymer via the lithiation of brominated polymer and reaction with a silyl electrophile. The degree of substitution of the silyl groups was 2.0 or less from dilithiated polymers and was dependent on the electrophile reactivity and reaction conditions. A detailed structural characterization of the polymers by NMR and IR spectroscopy is reported in addition to glass‐transition temperatures and thermal stabilities. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2103–2124, 2001
Block and star block copolymers by mechanism transformation. VI. Synthesis and characterization of A4B4 miktoarm star copolymers consisting of polystyrene and polytetrahydrofuran prepared by cationic ring‐opening polymerization and atom transfer radical polymerization
Authors: Guo Yan‐Ming , Pan Cai‐Yuan , Wang Jian
Published: October 2004

The synthesis of A4B4 miktoarm star copolymers, where A is polytetrahydrofuran (PTHF) and B is polystyrene (PSt), was accomplished with orthogonal initiators and consecutive cationic ring‐opening polymerization (CROP) and atom transfer radical polymerization (ATRP). The compound formed in situ from the reaction of 3‐{2,2‐bis[2‐bromo‐2‐(chlorocarbonyl) ethoxy] methyl‐3‐(2‐chlorocarbonyl) ethoxy} propoxyl‐2‐bromopropanoyl chloride [C(CH2OCH2CHBrCOCl)4] with silver perchlorate was used to initiate the CROP of tetrahydrofuran. The obtained polymer contained four secondary bromine groups at the α position to the original initiator sites and was used to initiate the ATRP of styrene with a CuBr/2,2′‐bipyridine catalyst to form a C(PTHF)4(PSt)4 miktoarm star copolymer. The miktoarm copolymer was characterized by gel permeation chromatography and 1H NMR. The macroinitiator C(PTHF)4Br4 was hydrolyzed to afford PTHF arms. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2134–2142, 2001
Low‐oxidation‐potential conducting polymers derived from 3,4‐ethylenedioxythiophene and dialkoxybenzenes
Authors: Irvin Jennifer A. , Schwendeman Irina , Lee Youngkwan , Abboud Khalil A. , Reynolds John R.
Published: October 2004

Monomers derived from 3,4‐ethylenedioxythiophene and phenylenes with branched or oligomeric ether dialkoxy substituents were prepared with the Negishi coupling technique. Electrooxidative polymerization led to the corresponding dialkoxy‐substituted 3,4‐ethylenedioxythiophene–phenylene polymers, with extremely low oxidation potentials (E1/2,p = −0.16 to −0.50 V vs Ag/Ag+) due to the highly electron‐rich nature of these materials. The polymers were electrochromic, reversibly switching from red to blue upon oxidation, with bandgaps at about 2 eV. The electrochemical behavior of the oligomeric ether‐substituted polymer was investigated in the presence of different metal ions. Films of the polymer exhibited electrochemical recognition for several alkali and alkaline‐earth cations with selectivity in the order Li+ > Ba2+ > Na+ > Mg2+. Cyclic voltammetry showed a decrease in the oxidation potential and an improvement in the definition of the voltammetric response, as well as an increase in the overall electroactivity of the polymer films when the concentration of the cations in the medium was increased. These results are discussed in terms of the electrostatic interactions between the complexed cation and the redox center, as well as the diffusion of the ionic species into the polymer matrix. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2164–2178, 2001
Synthesis of well‐defined cyclodextrin‐core star polymers
Authors: Ohno Kohji , Wong Benjamin , Haddleton David M.
Published: October 2004

The synthesis of 21‐arm methyl methacrylate (MMA) and styrene star polymers is reported. The copper (I)‐mediated living radical polymerization of MMA was carried out with a cyclodextrin‐core‐based initiator with 21 independent discrete initiation sites: heptakis[2,3,6‐tri‐O‐(2‐bromo‐2‐methylpropionyl]‐β‐cyclodextrin. Living polymerization occurred, providing well‐defined 21‐arm star polymers with predicted molecular weights calculated from the initiator concentration and the consumed monomer as well as low polydispersities [e.g., poly(methyl methacrylate) (PMMA), number‐average molecular weight (Mn) = 55,700, polydispersity index (PDI) = 1.07; Mn = 118,000, PDI = 1.06; polystyrene, Mn = 37,100, PDI = 1.15]. Functional methacrylate monomers containing poly(ethylene glycol), a glucose residue, and a tert‐amine group in the side chain were also polymerized in a similar fashion, leading to hydrophilic star polymers, again with good control over the molecular weight and polydispersity (Mn = 15,000, PDI = 1.03; Mn = 36,500, PDI = 1.14; and Mn = 139,000, PDI = 1.09, respectively). When styrene was used as the monomer, it was difficult to obtain well‐defined polystyrene stars at high molecular weights. This was due to the increased occurrence of side reactions such as star–star coupling and thermal (spontaneous) polymerization; however, low‐polydispersity polymers were achieved at relatively low conversions. Furthermore, a star block copolymer consisting of PMMA and poly(butyl methacrylate) was successfully synthesized with a star PMMA as a macroinitiator (Mn = 104,000, PDI = 1.05). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2206–2214, 2001
Synthesis, characterization, and thermal properties of ladderlike polyepoxysiloxanes
Authors: Lin Yuhui , Pramoda K. P. , He Chaobin , Chen Wei‐Yu , Chung T. S.
Published: October 2004

Starting from trichlorosilanes and using 1,4‐phenylenediamine as a template, we have synthesized some ladderlike poly(glycidyl‐co‐alkyl/aryl)siloxanes (polyepoxysiloxanes or polyepoxies for short). The structures of copolymers were confirmed through IR, 1H NMR, elemental analyses, and gel permeation chromatography. Curing behaviors of these polyepoxies in the absence and presence of a curing agent have been studied with DSC. It was shown that these epoxies could be cured without any curing agent. Copolymers having aromatic groups showed higher curing reactivity than those having alkyl groups. The experimental results also demonstrate that the curing reaction occurred solely via epoxy functionality, not via the condensation reaction of the hydroxy groups located at the end of polymer main chains. The thermal stability of the cured polymers was examined by thermogravimetric analysis. The results confirm that polyepoxies with aromatic groups had better thermal stability than those with alkyl groups. It was also found that polyepoxies cured with a diamine have a higher thermal stability than those cured in the absence of a curing agent. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2215–2222, 2001
Replacement of benzene with regulators for the catalyzed polymerization of 1,3‐butadiene to high cis‐1,4‐polybutadiene
Authors: Cass Peter , Pratt Kerry , Mann Terry , Laslett Bob , Rizzardo Ezio
Published: October 2004

The polymerization regulators mesitylene and 1,3,5‐trimethoxybenzene were investigated as suitable substitutes for benzene in the cobalt(II) octanoate/diethylaluminum chloride/water‐catalyzed polymerization of 1,3‐butadiene to high cis‐1,4‐polybutadiene. The propagation rates were reduced by 50% with the inclusion of 18 mM mesitylene or 0.17 mM trimethoxybenzene. Mesitylene was found to be an inefficient polymerization regulator because it reduced the propagation rate by a combination of regulation and destruction of the active catalyst complex. Not only did trimethoxybenzene reduce the propagation rate by effective regulation at low concentration, it also increased the percentage activity of cobalt to 200%, indicating that two polymer chains were propagating simultaneously from each active center. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2244–2255, 2001
Aromatic poly(1,3,4‐oxadiazole)s and poly(amide‐1,3,4‐oxadiazole)s containing ether sulfone linkages
Authors: Hsiao Sheng‐Huei , Chiou Jiun‐Hsiang
Published: October 2004

Polyhydrazides and poly(amide‐hydrazide)s were prepared from two ether‐sulfone‐dicarboxylic acids, 4,4′‐[sulfonylbis(1,4‐phenylene)dioxy]dibenzoic acid and 4,4′‐[sulfonylbis(2,6‐dimethyl‐1,4‐phenylene)dioxy]dibenzoic acid, or their diacyl chlorides with terephthalic dihydrazide, isophthalic dihydrazide, and p‐aminobenzhydrazide via a phosphorylation reaction or a low‐temperature solution polycondensation. All the hydrazide polymers were found to be amorphous according to X‐ray diffraction analysis. They were readily soluble in polar organic solvents such as N‐methyl‐2‐pyrrolidone and N,N‐dimethylacetamide and could afford colorless, flexible, and tough films with good mechanical strengths via solvent casting. These hydrazide polymers exhibited glass‐transition temperatures of 149–207 °C and could be thermally cyclodehydrated into the corresponding oxadiazole polymers in the solid state at elevated temperatures. Although the oxadiazole polymers showed a significantly decreased solubility with respect to their hydrazide prepolymers, some oxadiazole polymers were still organosoluble. The thermally converted oxadiazole polymers had glass‐transition temperatures of 217–255 °C and softening temperatures of 215–268 °C and did not show significant weight loss before 400 °C in nitrogen or air. For a comparative study, related sulfonyl polymers without the ether groups were also synthesized from 4,4′‐sulfonyldibenzoic acid and the hydrazide monomers by the same synthetic routes. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2271–2286, 2001
Formation of regioregular head‐to‐tail poly[3‐(4‐butylphenyl)thiophene] by an oxidative coupling polymerization with vanadium acetylacetonate
Authors: Hayakawa Teruaki , Fukukawa Ken‐Ichi , Morishima Makoto , Takeuchi Kazuhiko , Asai Michihiko , Ando Shinji , Ueda Mitsuru
Published: October 2004

The mechanism for the formation of head‐to‐tail (H–T) poly[3‐(4‐butylphenyl)thiophene] by oxidative coupling polymerization with a catalytic amount of vanadium acetylacetonate was investigated. Polymerization was carried out in the presence of vanadium acetylacetonate, trifluoromethane sulfonic acid, and trifluoroacetic anhydride under an oxygen atmosphere in 1,2‐dichloroethane at room temperature. Polymers and oligomers obtained after several polymerization times were characterized by gel permeation chromatography, IR, and NMR spectroscopies. With these findings and the reactivity of monomer and dimers based on ab initio density functional theory, the polymerization was found to proceed mainly through the formation of H–T linkages due to the high spin density at the 2‐position of 3‐(4‐butylphenyl)thiophene and the calculated total energy of dimers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2287–2295, 2001
End‐capped carbosilane dendrimers with benzoxazole, quinoline, and pyrone derivatives
Authors: Kim Chungkyun , Park Eunmi
Published: October 2004

Dendritic carbosilanes containing benzoxazole, quinoline, and pyrone derivatives on the periphery were prepared. The parent dendrimers in the inner shell were prepared by the use of iterative hydrosilation and alkenylation cycles. The end generations were obtained by the reaction of terminal SiCl groups on each periphery with HOR [HOR = 2‐(2‐hydroxyphenyl)‐benzoxazole, 8‐hydroxyquinoline, and 3‐hydroxy‐2‐methyl‐4‐pyrone] in the presence of amine. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2308–2314, 2001
Rigid‐chain metallomesogenic polymers containing vanadyl or copper(II) ions coordinated in the main chain
Authors: Caruso U. , Panunzi B. , Roviello A. , Sirigu A. , Spasiano D.
Published: October 2004

Rigid‐chain metallomesogenic polymers containing Cu(II) or VO(II) were prepared and characterized. All the polymers were soluble and melted without decomposition. They showed a thermotropic liquid–crystal (LC) behavior, and the mesophases were invariably preserved for a long time at room temperature in a metastable condition, with respect to the semicrystalline state. The nature of the mesophases of the Cu(II)‐containing polymers was similar to that observed in analogous organic rigid‐chain polymers having long lateral alkyl chains packed as extended ribbons. The VO(II)‐containing polymers showed an LC polymorphism involving a smectic A and a nematic phase. For all the polymers in a smectic or smecticlike state at room temperature, X‐ray diffraction data suggested short mean distances among the metal ions arranged in layers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2342–2349, 2001
1H NMR study of the kinetics of substituted aniline polymerization. II. Copolymerization of 2‐methoxyaniline and 3‐aminobenzenesulfonic acid
Authors: Mav Ida , Žigon Majda
Published: October 2004

We investigated the kinetics of the oxidative chemical copolymerization of 2‐methoxyaniline (OMA) and 3‐aminobenzenesulfonic acid (MA) by monitoring monomer depletion with 1H NMR spectroscopy. We adapted a semiempirical kinetic model, previously used for OMA homopolymerization, for the consumption of both OMA and MA monomers with a large difference in their reactivities. The OMA polymerization rate and end conversion showed a similar dependence on the reaction conditions, as described in the first part of this series, for its homopolymerization. Generally, the MA comonomer had an inhibition effect on the OMA polymerization rate. However, an increase in the initial MA concentration resulted in an increased OMA initiation rate. Because of the higher reactivity of OMA compared with that of MA, the OMA conversion began before the MA conversion, and both the initiation and propagation rates were higher than those for MA. The molar ratios of the converted monomers (MA/OMA) were always significantly lower than the corresponding MA/OMA feed fractions. They depended on the reaction conditions used for the copolymerization. In particular, higher oxidant or MA concentrations, higher temperatures, and a 1 M DCl concentration favored MA conversion, that is, its insertion into the copolymer. The MA end conversion was much smaller than that of OMA, only up to 23%; for a low oxidant concentration (oxidant/monomer‐deficient molar ratio), it was only 6%. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2482–2493, 2001
Equilibrium polymerization behavior in the cationic single ring‐opening polymerization of bicyclo orthoesters
Authors: Sanda Fumio , Hitomi Masakatsu , Endo Takeshi
Published: October 2004

The synthesis and cationic polymerization of the following bicyclo orthoesters were examined: 4‐ethyl‐2,6,7‐trioxabicyclo[2.2.2]octane, 1,4‐diethyl‐2,6,7‐trioxabicyclo[2.2.2]octane, 4‐ethyl‐1‐phenyl‐2,6,7‐trioxabicyclo[2.2.2]octane, 4‐ethyl‐1‐(4‐methoxyphenyl)‐2,6,7‐trioxabicyclo[2.2.2]octane, and 4‐ethyl‐1‐(4‐nitrophenyl)‐2,6,7‐ trioxabicyclo[2.2.2]octane. All the monomers underwent equilibrium polymerization, which was confirmed by the relationships between the polymerization temperature and monomer conversion. The obtained polymers afforded the original monomers via an acid‐catalyst treatment with a low reagent concentration in CH2Cl2 at 20 °C. The equilibrium monomer concentration was constant, regardless of the initial reagent concentration, in both polymerization and depolymerization. The bicyclo orthoesters with a bulky and electron‐withdrawing substituent showed a larger equilibrium monomer concentration. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3159–3167, 2001
Correlation between mechanical adhesion and interfacial properties of starch/biodegradable polyester blends
Authors: Biresaw G. , Carriere C. J.
Published: October 2004

Biopolymers are preferred ingredients for the manufacture of materials because they are based on abundantly available and renewable raw materials that have benign environmental problems associated with their production, fabrication, use, and disposal; however, the wide use of biopolymers in engineering applications has not been achieved, mainly because of the inferior quality of many biopolymer‐based products. To overcome this limitation, studies have been initiated on blends of biopolymers and biodegradable synthetic polymers. We used the contact angle of probe liquids to measure the surface energy of polystyrene, the biodegradable polyesters polycaprolactone, poly(hydroxybutyrate‐co‐hydroxyvalerate), polylactic acid, polybutylene adipate terephthalate, and adipic poly(hydroxy ester ether), and normal starch. The surface energies were used to estimate the starch/polymer interfacial energy and work of adhesion. The calculated starch/polyester work of adhesion showed mixed correlation with published starch/polyester mechanical properties, indicating that factors other than interfacial properties might be dominant in determining the mechanical properties of some starch/polyester blends. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 920–930, 2001
Water‐vapor permeation in semicrystalline and molten poly(octadecyl acrylate)
Authors: Mogri Z. , Paul D. R.
Published: October 2004

The water‐vapor permeability of poly(octadecyl acrylate) (PA‐18) was measured as a function of temperature in the region traversing its melting point (50 °C). The molten‐state permeability of PA‐18 is comparable to that of shorter side‐chain methacrylate polymers. Water permeability in the semicrystalline state of PA‐18 is similar to that of polyethylene at comparable crystallinity levels. The permeation switch, or change in permeability with the traversing of the melting point, for water is discussed in the context of previous results for other penetrants in this and other side‐chain crystalline polymers. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 979–984, 2001
Properties of nitrocellulose‐coated and polyethylene‐laminated chitosan and whey films
Authors: Gällstedt M. , Törnqvist J. , Hedenqvist M. S.
Published: October 2004

Chitosan (chitosan acetic acid salt) and whey (65% protein) films were coated with a nitrocellulose lacquer or laminated with polyethylene to enhance their water resistance and gas barrier properties in humid environments. The barrier properties were measured by the Cobb60test and water‐vapor (100% relative humidity) transmission and oxygen (90% relative humidity) permeability tests. Mechanical properties were obtained with tensile tests. Packaging properties were studied with crease and folding tests. The Cobb60test revealed that the coated films were resistant to liquid water, at least for a short exposure time, if the coating thickness was at least 10–17 μm. Water‐vapor transmission rates comparable to those of polyethylene‐laminated films were obtained for coated chitosan at a coating thickness of 5–7 μm. The coated films possessed low oxygen permeability despite the high humidity. Coated films dried for 3 weeks showed oxygen permeabilities at 90% relative humidity that were similar to values for dry ethylene‐co‐vinyl alcohol at 0% relative humidity. The lacquer partly penetrated the whey films, and this led to excellent adhesion but poor lacquer toughness. The lacquer coating on chitosan was tougher, and it was possible to fold these films 90° without the coating fracturing if the coating thickness was small. The coated whey films were readily creasable. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 985–992, 2001
Crystallization behavior of polypropylene with or without sodium benzoate as a nucleating agent
Authors: Jang Gu‐Su , Cho Won‐Jei , Ha Chang‐Sik
Published: October 2004

The crystallization kinetics of polypropylene (PP) with or without sodium benzoate as a nucleating agent were investigated by means of DSC and polarized optical microscopy in isothermal and nonisothermal modes. A modified Avrami equation was applied to the kinetic analysis of isothermal crystallization. The addition of the nucleating agent up to its saturation concentration increased the crystallization temperature by 15 °C and shortened both the isothermal and nonisothermal crystallization half‐times. It was concluded that the sodium benzoate acted as a good nucleating agent for α‐form PP. By adding the nuclefier to PP, adequately controlled spherulites increased the mechanical properties including especially the Izod impact strength and shortened cycle time of PP. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1001–1016, 2001
Synthesis and characterization of ion‐conducting polymer systems based on EPDM blends
Authors: Bashir H. , Linares A. , Acosta J. L.
Published: October 2004

This work reports the preparation and characterization of new polymeric ionomers based on etylene–propylene–diene copolymer (EPDM) with a high norbornene content. The sulfonation level was determined with X‐ray photoelectron spectroscopy, and the microstructural characterization was obtained through differential scanning calorimetry and dynamic mechanical analysis. In addition, the effects of certain plasticizers and polymers on the microstructures and conducting properties of these materials were studied, with special attention paid to the latter because of the interest aroused by these materials as membranes in polymer fuel cells. On the basis of the results, some of the synthesized membranes could be used for fuel cells because of their high conductivity (≥10−2 S/cm) and good dimensional stability (any shrinkage observed). © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1017–1026, 2001
Surface modification of polystyrene by blending substituted styrene copolymers
Authors: Chen Xianyi , Jankova Katja , Kops Joergen , Larsen Niels B. , Batsberg Walther , Johannsen Ib
Published: October 2004

The surface modification of polystyrene (PS) by the blending of 4‐acetoxystyrene polymers and their corresponding hydrolysis products, 4‐hydroxystyrene polymers, was investigated on the basis of X‐ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and contact‐angle measurements. According to XPS and AFM measurements, when polystyrene‐block‐poly(4‐acetoxystyrene) (PS‐b‐PAS) or polystyrene‐block‐poly(4‐hydroxystyrene) (PS‐b‐PHS) was incorporated into PS, the block copolymer was preferentially segregated at the highest surface region of the blend. This segregation increased to a plateau value when more than 5 wt % of either PS‐b‐PHS or PS‐b‐PAS was added. The contact angle of the modified PS by PS‐b‐PAS or PS‐b‐PHS was slightly lower than that of homopolystyrene, but no further decrease was observed with the blend ratio of the diblock copolymer increasing from 5 to 20 wt %. For a PS/PS‐b‐PHS blend, the surface atomic concentration ratio O/C increased linearly with the molecular weight of poly(4‐hydroxystyrene) blocks in diblock copolymer PS‐b‐PHS in the range of our study. The different structures of 4‐acetoxystyrene polymers and their hydrazinolyzed materials may affect the surface compositions of their blends with PS; among these polymers, PS‐b‐PHS and PS‐b‐PAS appeared to be most effective. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1046–1054, 2001
Control of bending electrostriction in polyurethane films by doping with salt
Authors: Watanabe Masashi , Kato Takahiro , Suzuki Makoto , Hirako Yoshiyuki , Shirai Hirofusa , Hirai Toshihiro
Published: October 2004

We systematically investigated the effect of doping with salt on the bending electrostriction in polyurethane films. When a film was doped with sodium acetate, it was bent toward the cathode side by the application of an electric field. However, when a film was doped with zinc bromide, it was bent toward the anode side. Thus, we found a way of controlling the bending direction. We also investigated the mechanism of the effect of the doping. Doping is believed to be a treatment that can control the bending deformation through modification of the charge injection, the major origin of the deformation. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1061–1069, 2001
Reversible and irreversible heat capacity of poly[carbonyl(ethylene‐co‐propylene)] by temperature‐modulated calorimetry
Authors: Pyda M. , Di Lorenzo M. L. , Pak J. , Kamasa P. , Buzin A. , Grebowicz J. , Wunderlich B.
Published: October 2004

The heat capacity of poly[carbonyl(ethylene‐co‐propylene)] with 95 mol % C2H4CO (Carilon EP®) was measured with standard differential scanning calorimetry (DSC) and temperature‐modulated DSC (TMDSC). The integral functions of enthalpy, entropy, and free enthalpy were derived. With quasi‐isothermal TMDSC, the apparent reversing heat capacity was determined from 220 to 570 K, including the glass‐ and melting‐transition regions. The vibrational heat capacity of the solid and the heat capacity of the liquid served as baselines for the quantitative analysis. A small amount of apparent reversing latent heat was found in the melting range, just as for other polymers similarly analyzed. With an analysis of the heat‐flow rates in the time domain, information was collected about latent heat contributions due to annealing, melting, and crystallization. The latent heat decreased with time to an even smaller but truly reversible latent heat contribution. The main melting was fully irreversible. All contributions are discussed in the framework of a suggested scheme of six physical contributions to the apparent heat capacity. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1565–1577, 2001
Comparison of semicrystalline ethylene–styrene and ethylene–octene copolymers based on comonomer content
Authors: Chen H. Y. , Chum S. P. , Hiltner A. , Baer E.
Published: October 2004

The structure and properties of homogeneous copolymers of ethylene and styrene (ES) and ethylene and octene (EO) were compared. Semicrystalline copolymers presented a broad spectrum of solid‐state structures from highly crystalline, lamellar morphologies to the granular, fringed micellar morphology of low‐crystallinity copolymers. The combined observations from density, thermal behavior, and morphology with primarily atomic force microscopy revealed that the crystalline phase depended on the amount of comonomer but was not strongly affected by whether the comonomer was styrene or octene. This was consistent with the exclusion of both comonomers from the crystal. However, ES and EO showed strong differences in the amorphous phase. ES had a much higher β‐relaxation temperature than EO, which was attributed to restrictions on chain mobility imposed by the bulky phenyl side group. The deformation behavior of ES and EO exhibited the same trends with comonomer content, from necking and cold drawing typical of a semicrystalline thermoplastic to uniform drawing and high recovery characteristic of an elastomer. Aspects of deformation behavior that depended on crystallinity, such as yielding and cold drawing, were determined primarily by comonomer content. However, the difference in the β‐relaxation temperature resulted in much higher strain hardening of ES than EO. This was particularly evident with low‐crystallinity, elastomeric copolymers. A classification scheme for semicrystalline copolymers based on comonomer content, previously developed for EO, was remarkably applicable to ES. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1578–1593, 2001
Crystallizability of ethylene homopolymers by crystallization analysis fractionation
Authors: Nieto J. , Oswald T. , Blanco F. , Soares Joao B. P. , Monrabal Benjamin
Published: October 2004

The effect of molecular weight and long‐chain branching on the crystallization analysis fractionation (CRYSTAF) of ethylene homopolymers was investigated. Several ethylene homopolymers were prepared with different molecular weights and levels of long‐chain branching to isolate these effects from the dominant effect of comonomer content on crystallizability measured by CRYSTAF. Molecular weight effects might be significant for samples with number‐average molecular weights below 5000, but this effect can be corrected if terminal methyl groups are taken into account. Long‐chain branching has only a very small effect on the CRYSTAF profile of the samples investigated in this study. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1616–1628, 2001
Changes in superstructure and mechanical properties of poly(ethylene‐2,6‐naphthalate) fibers with critical necking tension
Authors: Suzuki Akihiro , Kawada Takashi , Hasegawa Toshinori
Published: October 2004

Poly(ethylene‐2,6‐naphthalate) fibers were zone‐drawn under a critical necking tension (σc) defined as the minimum tension needed to generate a necking at a given drawing temperature (Td). In the zone drawing under σc, the neck was observed from 110 to 160 °C. The superstructure in a neck zone induced at each Td was studied. The σc value decreased exponentially with increasing Td and dropped to a low level at a higher Td. The draw ratio increased rapidly with Td increasing above 90 °C, but the birefringence and degree of crystallinity decreased gradually. To study the molecular orientation in the neck zone, we measured a dichroic ratio (A‖/A⟂) of a CO band at 1256 cm−1 along a drawing direction in the neck zone with a Fourier transform infrared microscope. A‖/A⟂ at Td = 110 °C increased rapidly in the narrow neck zone, and that at Td = 140 °C increased in the edge of the wide neck zone. Wide‐angle X‐ray diffraction patterns of the fibers obtained at Td = 130 °C and lower showed three reflections due to an α form, but those at Td = 140 and 150 °C had reflections due to the α form and a β form. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1629–1637, 2001
Confirmation of universality of time–humidity superposition principle for various water‐absorbable polymers through dynamic viscoelastic measurements under controlled conditions of relative humidity and temperature
Authors: Zhou S.‐M. , Tashiro K. , Ii T.
Published: October 2004

Dynamic viscoelastic measurements were made for storage (E′) and loss (E″) tensile moduli of water‐absorbable polymers such as nylon‐6, nylon‐66, poly(vinyl alcohol), ethylene–vinyl alcohol copolymers, and regenerated cellulose under the control of stepwise scanned relative humidity at constant temperature by changes in the strain frequency over a wide range. Smooth master curves of log(E′) and log(E″) plotted against log(frequency) were successfully obtained for all samples. The evaluated shift factors changed with the relative humidity and could be interpreted well on the basis of a concept of free volume in the amorphous region. The free volume was affected sensitively, depending on the heat‐treatment condition and the types of polymers used. For nylon‐66 film, the dynamic viscoelastic measurements were made at different humidities and temperatures, from which one smooth master curve was obtained. This experimental result is important in realizing the similar effect of relative humidity and temperature on the expansion of free volume of the amorphous phase: the shift factor change induced by the relative humidity change of about 30% was equivalent to the shift factor change induced by the temperature change of about 30 °C. That is, the time–humidity superposition principle and the time–temperature superposition principle were applicable as equivalent contributors to the mechanical property of water‐absorbable polymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1638–1650, 2001
Screening effects in blends of a hyperbranched, dendrimer‐like polyester with poly(4‐vinyl phenol)
Authors: Pruthtikul Rittirong , Coleman Michael M. , Painter Paul C. , Beck Tan Nora
Published: October 2004

We previously reported self‐association and interassociation equilibrium constant values describing hydrogen bonding in solutions of a hyperbranched polyester. These allow us to estimate the extent of intramolecular screening and the fraction of same‐chain contacts in this system as a function of generation number. In this article, we use a similar method to evaluate the degree of intramolecular screening in polymer blends. The calculated values reported here are consistent with those previously reported in our solution study, confirming the validity of the calculation procedures we used to evaluate the accessibility of functional groups in these highly branched systems. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1651–1658, 2001
Effect of residual water and free volume on the glass‐transition temperature and heat capacity in polystyrene/poly(vinyl acetate‐co‐butyl acrylate) structured latex films
Authors: Song M. , Hourston D. J. , Silva G. G. , Machado J. C.
Published: October 2004

The dynamic heat capacity and glass‐transition temperature of polystyrene (PS)/poly(vinyl acetate‐co‐butyl acrylate) (VAc–BA) (50:50 w/w) structured latex films as a function of annealing time at 70, 77, and 85 °C were examined with modulated‐temperature differential scanning calorimetry. The PS and poly(vinyl acetate‐co‐n‐butyl acrylate) components were considered to be the cores and shells, respectively, in the structured latex. The dynamic heat capacity decreased with time. The glass‐transition temperatures of the PS and VAc–BA phases shifted to higher values after annealing. The results of thermogravimetry showed that there existed about 1.8% residual water in the films. The mean free volume and relative concentration of holes at room temperature (before and after annealing) and 85 °C, as a function of time, were obtained with positron annihilation lifetime spectroscopy (PALS). The PALS results indicated no significant change in free volume during annealing. It is believed that the loss, by diffusion, of residual water mainly caused a decrease in heat capacity and an increase in the glass‐transition temperatures. As little as 1.8% residual water in the structured latex films had a significant influence on the thermal properties. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1659–1664, 2001
Attenuated total reflectance/fourier transform infrared studies on the phase‐separation process of aqueous solutions of poly(n‐isopropylacrylamide)
Authors: Ramon Ory , Kesselman Ellina , Berkovici Ronen , Cohen Yachin , Paz Yaron
Published: October 2004

Temperature‐induced phase separation of poly(N‐isopropylacrylamide) in aqueous solutions was studied by attenuated total reflectance (ATR)/Fourier transform infrared spectroscopy. The main objectives of the study were to understand, on a molecular level, the role of hydrogen bonding and hydrophobic effects below and above the phase‐separation temperature and to derive the scenario leading to this process. Understanding the behavior of this particular system could be quite relevant to many biological phenomena, such as protein denaturation. The temperature‐induced phase transition was easily detected by the ATR method. A sharp increase in the peaks of both hydrophobic and hydrophilic groups of the polymer and a decrease in the water‐related signals could be explained in terms of the formation of a polymer‐enriched film near the ATR crystal. Deconvolution of the amide I and amide II peaks and the OH stretch envelope of water revealed that the phase‐separation scenario could be divided, below the phase‐separation temperature, into two steps. The first step consisted of the breaking of intermolecular hydrogen bonds between the amide groups of the polymer and the solvent and the formation of free amide groups, and the second step consisted of an increase in intramolecular hydrogen bonding, which induced a coil–globule transition. No changes in the hydrophobic signals below the separation temperature could be observed, suggesting that hydrophobic interactions played a dominant role during the aggregation of the collapsed chains but not before. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1665–1677, 2001
Molecular motion in nanocomposites of poly(ethylene oxide) and montmorillonite
Authors: Kwiatkowski Johann , Whittaker Andrew K.
Published: October 2004

Motion of chains of poly(ethylene oxide) within the interlayer spacing of 2:1 phyllosilicate/montmorillonite was studied with 1H and 13C NMR spectroscopy. Measurements of the 1H NMR line widths and relaxation times across a large temperature range were used to determine the effect of bulk thermal transitions on polymer chain motion within the nanocomposites. The results were consistent with previous reports of low apparent activation energies of motion. Details of the frequency and geometry of motion were obtained from a comparison of the 13C cross‐polarity/magic‐angle spinning spectra and relaxation times of the nanocomposite with those of the pure polymer. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1678–1685, 2001
Effect of crosslinking on the photoinduced orientation of azo groups in thin polymer films
Authors: Takase Hideaki , Natansohn Almeria , Rochon Paul
Published: October 2004

A series of amorphous copolymers containing disperse red 1 and crosslinkable acrylic groups were prepared. The crosslinked polymers were prepared in thin films by thermal polymerization of the acrylic groups in the copolymers. The orientation induced by irradiation with a linearly polarized laser was measured as birefringence at several temperatures, and the effect of crosslinking on the photoinduced orientation was investigated. Crosslinking enhanced the stability of the photoinduced birefringence. In particular, crosslinking helped to maintain the birefringence both at high temperatures and after the linearly polarized laser was turned off. The birefringence dynamics was analyzed with biexponential curve fitting. Crosslinking influenced not only the birefringence levels but also its rate of growth. The growth rate of the photoinduced birefringence decreased by crosslinking, whereas the relaxation was not significantly affected. Although crosslinking restrained the mobility of the azo chromophores, a certain fraction could orient or move randomly even in highly crosslinked polymer networks. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1686–1696, 2001
Organic light‐emitting device dark spot growth behavior analysis by diffusion reaction theory
Authors: Ke Lin , Lim Shuang Fang , Chua Soo Jin
Published: October 2004

Dark spot growth rate tracing experiments performed on an organic light‐emitting device show that moisture entering into the device is relatively properly fitted by Fick's diffusion equation in the substrate/indium tin oxide (ITO)/hole transport layer (HTL)/silver (Ag) structure. It is believed that the moisture is dissolved into the polymer layer, which results in a decrease in the diffusion coefficient in the device with the substrate/ITO/HTL/electroluminescent (EL) polymer/Ag structure. The diffusion and chemical reaction occurring in the cathode layer further decreases the diffusion coefficient in the device with the substrate/ITO/HTL/EL polymer/calcium/Ag structure. Useful parameters, such as diffusion and solubility constants, describing possible mechanisms happening during dark spot growth on organic light‐emitting diode devices are extracted. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1697–1703, 2001
Oxygen‐barrier properties of copolymers based on ethylene terephthalate
Authors: Polyakova A. , Liu R. Y. F. , Schiraldi D. A. , Hiltner A. , Baer E.
Published: October 2004

The oxygen‐barrier properties of amorphous polyethylene terephthalate‐based copolymers with various acid comonomers were examined. The incorporation of increasing amounts of isophthalate, phthalate, or naphthalate gradually reduced the permeability P toward the low values obtained for the corresponding homopolymers. The permeability of poly(ethylene 3,4′‐bibenzoate) homopolymer was only slightly lower than that of polyethylene terephthalate, and the copolymers correspondingly exhibited a very gradual decrease in P as the amount of 3,4′‐bibenzoate (3,4′BB) increased. In contrast, copolymerization with the linear isomer, 4,4′BB, produced a substantial increase in P. Generally, comonomer affected the solubility S less than the diffusivity D, and therefore changes in P reflected primarily changes in D for the polymers studied. The diffusivity and solubility depended on the copolymer composition in accordance with static and dynamic free‐volume concepts of gas permeability in glassy polymers. The solubility S correlated with the amount of free volume as determined by the glass‐transition temperature. Correlation of the diffusivity D with the magnitude of the subambient γ relaxation identified dynamic free volume with thermally activated conformational changes and segmental motions. Correspondence in the activation energy confirmed the relationship. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1889–1899, 2001