bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis, characterization, and crosslinking of novel stars comprising eight poly(isobutylene‐azeotropic‐styrene) copolymer arms with allyl or hydroxyl termini. I. Living azeotropic copolymerization of isobutylene and styrene
Authors: Hull Diana L. , Kennedy Joseph P. 
Published: August 2002

AbstractThe overall objective of this research is the creation of novel star polymers consisting of well‐defined stable cores out of which radiate multiple poly(isobutylene‐co‐styrene) [P(IB‐co‐St)] arms whose glass‐transition temperature (Tg) can be controlled over a wide range (−73 to +100 °C) and whose arm termini are fitted with multipurpose (e.g., crosslinkable) functionalities. The first article of this series relates the synthesis and characterization of azeotropic IB/St copolymers [P(IB‐aze‐St)], which are to be subsequently used as end‐functional arms of the target stars. The P(IB‐aze‐St)s are models for statistical IB/St copolymers. The azeotropic composition is 21/79 (mol/mol) IB/St, and NMR, Fourier transform infrared, and gel permeation chromatography techniques demonstrate copolymer compositional homogeneity over the 12–96% conversion range. Conditions were developed for living azeotropic IB/St copolymerization. The livingness of the azeotropic copolymerization was proven by kinetic investigations. P(IB‐aze‐St)s with number‐average molecular weights of up to 24,000 g/mol and polydispersity indices (weight‐average molecular weight/number‐average molecular weight) less than 1.5 were prepared. The copolymerization reactivity ratios were determined: rIB = 3.41 ± 0.23 and rSt = 1.40 ± 0.26. The effect of the P(IB‐aze‐St) molecular weight on Tg was studied by DSC. Tg increases linearly with the number‐average molecular weight and reaches a plateau at 62 °C at 24,000 g/mol. The heat stability of P(IB‐aze‐St) was investigated by thermogravimetric analysis, and a 5% weight loss was found at 250 °C in air. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1515–1524, 2001
Preparing organosoluble aromatic polyimides based on 3,3′,5,5′‐tetrabromo‐2,2‐bis[4‐(4‐aminophenoxy)phenyl]propane and aromatic dianhydrides
Authors: Hung Kuo‐Yuan , Tsiang Raymond Chien‐Chao 
Published: August 2002

AbstractA new aromatic diamine, with an isopropylidene and bromo‐substituted arylene ether structure, 3,3′,5,5′‐tetrabromo‐2,2‐bis[4‐(4‐aminophenoxy)phenyl]propane, was synthesized by the nucleophilic substitution reaction of p‐chloronitrobenzene with 3,3′,5,5′‐tetrabromobisphenol A, followed by a catalytic reduction of the resulting dinitro compound. Novel aromatic polyimides with inherent viscosities ranging from 0.53 to 2.1 dL/g were then obtained by a one‐step or two‐step polymerization process with this diamine and various aromatic dianhydrides. These bromine‐containing polyimides showed typical amorphous diffraction patterns and were readily soluble at room temperature in N‐methyl‐2‐pyrrolidone, N,N′‐dimethylformamide, N,N′‐dimethylacetamide, and even in less polar solvents such as chloroform, tetrahydrofuran, and pyridine. They also dissolved in dimethyl sulfoxide, m‐cresol, o‐chlorophenol, or concentrated sulfuric acid with heating. Glass‐transition temperatures were 272–303 °C, depending on the nature of the dianhydride moiety. Thermogravimetric analysis showed that all the polymers were thermally stable, with 10% weight loss occurring between 465 and 499 °C in nitrogen and between 457 and 492 °C under atmospheric conditions. The bulky bromine substituents not only increased the solubility but also compensated for the loss of thermal properties caused by the flexible ether linkage. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1662–1674, 2001
Syntheses and characterizations of bis(trialkoxysilyl)oligoimides. II. Syntheses and characterizations of fluorinated crosslinkable oligoimides with low refractive indices
Authors: Bes L. , Rousseau A. , Boutevin B. , Mercier R. 
Published: August 2002

AbstractNovel crosslinkable fluorinated oligoimides were prepared in two steps. The first involved the synthesis of oligoimides terminated with nadic or allylic double bonds, and the second step was materialized either by a radical addition of mercaptotrialkoxysilane derivatives onto nadic double bonds or a hydrosilylation reaction of hydrogenotrialkoxysilane derivative onto allylic double bonds. Three kinds of crosslinking of the trialkoxysilane end groups were studied. The first kind entailed a thermal self‐crosslinking of trialkoxysilane groups. The second process of crosslinking incorporated a bicomponent system—the crosslinked agent was 1,1,1‐tris(4‐hydroxyphenyl)ethane (TRIOH). The trialkoxysilane groups reacted with the hydroxyl–phenol groups of TRIOH to give thermally stable phenoxysilane bonds as well as a crosslinking network. The last method was also a bicomponent system; the oxalic acid was added into an oligoimide solution where by thermal treatment water was created. The water molecules hydrolyzed the trialkoxysilane groups into silanol groups that polycondensed into a crosslinked network following a sol–gel process. The mechanism of the different crosslinking reactions was investigated by Fourier transform infrared spectroscopy and solid‐state 29Si NMR. The self‐crosslinked material prepared from precursor α,ω‐trimethoxysilyl fluorinated oligomer (Mn = 5500 g · mol−1) exhibited a 10 wt % loss temperature under air higher than 420 °C and a low birefringence (Δn = 0.008) at 1.300 μm. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2602–2619, 2001
Stabilization and kinetics in the emulsion copolymerization of butyl acrylate and methyl methacrylate
Authors: Ouzineb K. , Heredia M. Fortuny , Graillat C. , Mckenna T. F. 
Published: August 2002

AbstractWe carried out emulsion homopolymerizations and copolymerizations of butyl acrylate (BuA) and methyl methacrylate (MMA) with different types and concentrations of surfactants to determine the influence of these parameters on the particle size and particle size distribution and to elucidate the mechanism of particle formation. As expected, the mechanisms of nucleation above and below the critical micelle concentration were very different; however, it was also found that the presence of partially soluble monomers such as MMA in the water phase had a significant influence on the critical micelle concentration of Triton X‐405 (>50%). In addition, the nucleation mechanism during copolymerization seemed to be dominated by BuA, with the number of particles per liter being very similar to the number nucleated during its homopolymerization. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2832–2846, 2001
Preparation and characterization of novel basic polysulfone polymers
Authors: Kerres Jochen , Ullrich Andreas , Hein Martin 
Published: August 2002

AbstractTwo synthesis routes for the preparation of novel base‐modified polysulfones (PSUs; Udel®) were investigated: (1) the addition of the basic aromatic ketones 2,2′‐dipyridylketone and 4,4′‐bis‐(diethylamino)benzophenone and the basic aromatic aldehydes N,N‐dimethylamino‐benzaldehyde, pyridine‐2‐aldehyde, pyridine‐3‐aldehyde, and pyridine‐4‐aldehyde to lithiated PSU and (2) the reaction of lithiated PSU with basic aromatic carboxylic acid esters such as 4‐N,N‐dimethylaminobenzoic acid ethylester, pyridine‐2‐carboxylic acid ethylester, pyridine‐3‐carboxylic acid ethylester, and pyridine‐4‐carboxylic acid ethylester. Both synthesis routes lead to a high degree of conversion, without the occurrence of crosslinking. This is remarkable, especially for the reaction of lithiated PSU with the ester compounds, because the (CO)Ar groups formed by the reaction of the ester with PSU–Li are not further converted with the remaining PSU–Li sites to (crosslinked) PSUC(OLi)ArPSU alcoholates, as normally observed when esters are reacted with Li‐organic compounds. Starting with dilithiated PSU, we obtained degrees of substitution of 0.8–2 groups per PSU repeating unit. The structures and compositions of the modified PSU polymers were confirmed with NMR spectroscopy and elemental analysis. The modified polymers were also characterized via thermogravimetric analysis (thermal stability). Interestingly, the product of the reaction of lithiated PSU with 4,4′‐bis‐(diethylamino)benzophenone could be oxidized to a deep blue polymeric dye that showed proton self‐conductivity. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2874–2888, 2001
End‐functionalized copolymers prepared by the addition–fragmentation chain‐transfer method: Vinyl acetate/methacrylonitrile system
Authors: Busfield W. Ken , Zayas‐Holdsworth Clovia I. , Thang San. H. 
Published: August 2002

AbstractCopolymers of vinyl acetate and methacrylonitrile were prepared by free‐radical polymerization in the presence of the chain‐transfer agent (CTA) ethyl‐α‐ (t‐butanethiomethyl)acrylate. Molecular weight measurements showed that the chain‐transfer constants increased with the vinyl acetate content of the comonomer mixture, ranging from 0.42 for methacrylonitrile to 6.3 for the copolymerization of a vinyl acetate‐rich monomer mix (89/11). The bulk copolymer composition was not appreciably affected by the amount of CTA used in the copolymerization. The efficiency of the addition–fragmentation mechanism in producing specifically end‐functionalized copolymers was investigated with 1H NMR spectroscopy. Spectral peaks consistent with all the expected end groups were observed for all comonomer feeds. Peaks consistent with other end groups were also observed, and these were particularly prominent for copolymers made with lower CTA concentrations. At the highest concentrations used, quantitative measurements of end‐group concentrations indicated that 70–80% of the end groups were those expected on the basis of the addition–fragmentation chain‐transfer mechanism. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2911–2919, 2001
Synthesis and properties of poly‐(2‐ethynylpyridinium bromide) having propargyl side chains
Authors: Gal Yeong‐Soon , Lee Won‐Chul , Kim Sang‐Yul , Park Jong‐Wook , Jin Sung‐Ho , Koh Kwang‐Nak , Kim Sung‐Hoon 
Published: August 2002

AbstractPoly‐(2‐ethynylpyridinum bromide) (PEPBP) having propargyl side chains was prepared by the direct polymerization of 2‐ethynylpyridine and propargyl bromide under mild reaction conditions without any initiator and catalysts. The polymerization proceeded well to give PEPBP with propargyl side chains in relatively high yields. Various spectral data for the polymer structure indicated that the conjugated polymer system having N‐propargylpyridinum substituent was formed. This ionic polymer was completely soluble in water, methanol, dimethylformamide, dimethyl sulfoxide, and N,N‐dimethylacetamide and well processable into thin homogeneous film. The photoluminescence intensity (λmax = 760 nm) of this polymer increased as the temperature was increased. At 1 KHz and room temperature, this polymer has k′ = 2.9 and σ = 7.3 × 10−10 (S/cm). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3151–3158, 2001
Anomalous solubility of polyacrylamide prepared by dispersion (precipitation) polymerization in aqueous tert‐butyl alcohol
Authors: Guha Suparna , Ray Biswajit , Mandal Broja M. 
Published: August 2002

AbstractPolyacrylamide prepared by dispersion (precipitation) polymerization in an aqueous t‐butyl alcohol (TBA) medium is only partially soluble when the TBA concentrations in the polymerization media are in the range 82 vol % < TBA < 95 vol %. Independent experiments with a soluble (linear) sample of polyacrylamide show that the polymer swells sufficiently in the aforementioned media to lower the glass‐transition temperature of the polymer below the polymerization temperature (50 °C). The anomalous solubility has been attributed to the crosslinking of polymer chains that occurs during the solid‐phase polymerization of acrylamide in the swollen polymer particles. It is postulated that some of the radical centers shift from the chain end to the chain backbone during solid‐phase polymerization by chain transfer to neighboring polymer molecules, and when pairs of such radicals come into close vicinity, crosslinking occurs. However, dispersion (precipitation) polymerization in other media such as aqueous methanol and aqueous acetone yields polymers that are soluble. This result has been attributed to the fact that the polymer radical undergoes a chain‐transfer reaction with these solvents at a much faster rate than with TBA, which overcomes the effect of the polymer‐transfer reaction. Even the addition of as little as 5% methanol to a TBA–water mixture (TBA:water = 85:10) gives rise to a soluble polymer. The chain‐transfer constants for acetone, methanol, and TBA have been determined to be 9.0 × 10−6, 6.9 × 10−6, and 1.48 × 10−6, respectively, at 50 °C. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3434–3442, 2001
Semi‐interpenetrating polymer networks based on polyurethane and polymethacrylate functional prepolymers: Morphology and mechanical properties in dependence of the concentration of functional groups
Authors: Anžlovar Alojz , Žigon Majda 
Published: August 2002

AbstractGrafted semi‐interpenetrating polymer networks (IPNs) were prepared from polyurethane (PU) prepolymers with polyester soft segments and hard segments containing carboxylic functional groups as well as polymethacrylate (PM) prepolymers with tertiary amine functional groups. The dependence of morphological and mechanical properties on the concentration of functional groups was studied. The enhanced miscibility of PU and PM prepolymers was observed at concentrations of functional groups of 0.25 mmol/g of polymer and above. Despite the improved miscibility, the PM prepolymers showed a tendency toward phase separation. Because the observed glass‐transition temperature shifts of PU prepolymers indicated substantial miscibility, we ascribed this phenomenon to the presence of methyl methacrylate rich sequences in the PM prepolymer. The observed changes in mechanical properties by increasing the content of functional groups were typical for ionomers. Young's modulus increased as a result of physical interactions between functional groups. A significant drop in tensile strength was observed in IPN samples with phase‐separated PU and PM prepolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 115–123, 2002
Novel etching phenomena in poly(3‐hydroxy butyrate) and poly(oxymethylene) spherulites
Authors: Shahin M. M. , Olley R. H. 
Published: August 2002

AbstractPoly‐3‐hydroxy butyrate has been etched and studied under scanning and transmission electron microscopes. It displays three of the following unusual features: (1) spherulites develop in a loose spiral rather than radial structure, which appears to reflect the chiral nature of the polymer; (2) in the banded spherulitic structure, lamellae oriented flat‐on to the surface are etched more deeply in relation to edge‐on lamellae; and (3) material crystallized at high temperature is less resistant to etching than that crystallized at low temperature, whereas the most rapid rate of etching appears to be where growth occurred at an intermediate temperature where the growth rate was at its maximum. The second and third phenomena are contrary to what is found in polymers such as polyethylene and polyethylene terephthalate and are attributed to excess free volume in the material located between the main lamellar bundles. Polyoxymethylene also displays the same unusual relationship of etching rate with crystallization temperature. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 124–133, 2002
Angular dependence in the transmittance from self‐organized striped pattern of refractive indices in photopolymer
Authors: Uematsu Takafumi , Maenosono Shinya , Watanabe Akira , Yamaguchi Yukio 
Published: August 2002

AbstractWe report on a self‐organized striped pattern of refractive indices in a photopolymer and the resulting angular dependence in the transmittance as a result of the microstructure. The photopolymer plates were obtained by photoreaction of a monomer mixture placed in a space between two glass plates. The monomer mixture was prepared by mixing bifunctional methacrylate monomer, cyanoethylmethacrylate, and 2,4,6‐trimethylbenzoyldiphenylphosphine oxide as photoinitiator. After the photoreaction by uniform irradiation of UV light, the self‐organized striped pattern was observed in the crosslinked photopolymer plate by optical microscopy. Electron probe microanalysis of the cross section of the polymer plate confirms that a compositional inhomogeneity in the medium is quite small. The result suggests that the optically observed striped pattern is not due to the compositional and/or density modulation through the diffusion of monomers. We attribute the striped pattern to the crosslink density modulation and the resulting refractive‐index modulation. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 216–225, 2002
Microphase separation in poly(acrylonitrile–butadiene–styrene) (ABS) studied with paramagnetic spin probes. II. Simulation of electron spin resonance spectra
Authors: Varghese Biji , Schlick Shulamith 
Published: August 2002

AbstractWe recently presented electron spin resonance spectra of poly(acrylonitrile–butadiene–styrene) (ABS) doped with 10‐doxylnonadecane (10DND) and 5‐doxyldecane (5DD) as spin probes. The spectra were measured in three types of ABS that differed in their butadiene contents and methods of preparation. Results for the ABS polymers were evaluated by comparison with similar studies on the homopolymers polybutadiene (PB) and polystyrene (PS) and the copolymers poly(styrene‐co‐acrylonitrile) (SAN) and poly(styrene‐co‐butadiene) (SB). Only one spectral component was detected for 10DND in PB, PS, SAN, and SB. In contrast, two spectral components differing in their dynamic properties were detected in the ABS samples and were assigned to spin probes located in butadiene‐rich domains (the fast component) and SAN‐rich domains (the slow component). The presence of two spectral components was taken as an indication of microphase separation. In this study, we present details on the dynamics and microphase separation by simulating spectra of 10DND in ABS, PB, PS, and SAN. The simulations are based on a dynamic model defined by the components of the rotational diffusion tensor and the diffusion tilt angle between the symmetry axis of the rotational diffusion tensor and the direction of the nitrogen 2pz atomic orbital. The jump diffusion model led to good agreement with experimental spectra. In this model, the spin probe has a fixed orientation for a given time and then jumps instantaneously to a new orientation. The temperature variation of the rotational correlation time in PB and PS consisted of two dynamic regimes, with different activation energies. The transition temperature at which the change in dynamics occurs (Ttr) is 380 K for PS and 205 K for PB, essentially the same as the corresponding glass‐transition temperatures measured by differential scanning calorimetry. We suggest that Ttr is a better indicator of the glass transition than the temperature at which the total spectral width is 50 G, especially for large probes. The simulation program allowed the determination of the relative intensities of the fast and slow spectral components as a function of temperature; this information was used to clarify the redistribution of the probe above the glass transition of the SAN‐rich component in ABS systems. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 424–433, 2002; DOI 10.1002/polb.10110
Diffusion measurements with fourier transform infrared attenuated total reflectance spectroscopy: Water diffusion in polypropylene*
Authors: Yi Xiaohua , Pellegrino John 
Published: August 2002

AbstractThe diffusion of pure liquid water into a commercial polypropylene (PP) film at 278–348 K was studied with Fourier transform infrared attenuated total reflectance spectroscopy. Abnormal diffusion behavior was indicated by a significant deviation between the experimental data and a Fickian diffusion model with the conventional saturated boundary condition applied at the water/PP interface. This deviation was observed at all the temperatures studied. With a modified boundary condition that took into account a mass‐transfer resistance at the water/PP interface, the Fickian model was able to represent the experimental data satisfactorily. The average water diffusion coefficient varied between 1.41 and 7.64 × 10−9 cm2/s, with an activation energy of diffusion of about 19.3 kJ/mol. The interfacial mass‐transfer resistance was represented by an exponential model with an empirical relaxation parameter. The relaxation parameter β increased as the temperature increased and reached an apparent plateau. The infrared spectrum indicated a positive chemical shift of 18 cm−1 for the less strongly hydrogen‐bonded component of the broad hydroxyl stretching band with respect to pure liquid water, indicating that hydrogen‐bonding interactions were weakened or broken when water molecules diffused into the PP matrix. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 980–991, 2002
Interaction mechanism of a novel polymer electrolyte composed of poly(acrylonitrile), lithium triflate, and mineral clay
Authors: Chen Hsien‐Wei , Chang Feng‐Chih 
Published: August 2002

AbstractThe addition of optimum cetyl pyridium chloride (CPC)–modified montmorillonite (CM) increases the ionic conductivity of poly(acrylonitrile)‐based electrolytes by roughly two orders of magnitude. Specific interactions between the silicate layer, the nitrile group, and the lithium cation were investigated by FTIR, solid‐state NMR, dielectric analyzer, and alternating current impedance. IR and NMR spectra confirm that the negative charges in the silicate layers alter the ionic charge environment of the PAN‐based electrolyte composites, which have the same function as the polar group in PAN. The optimum CM content to achieve the maximum ionic conductivity is 6 phr. However, untreated montmorillonite leads to insignificant polymer intercalation, the negative charges in the silicate layers fail to appreciably disturb the attractive force of the lithium salt, and the resulting conductivity improvement is also less than that of the CM additives. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2407–2419, 2001
Simulation of two‐dimensional streptavidin crystallization
Authors: Zhdanov V.P. , Höök F. , Kasemo B. 
Published: August 2002

AbstractWe present lattice Monte Carlo simulations of the growth of streptavidin islands at a biotinylated lipid layer. The model employed takes into account attractive anisotropic lateral interactions between streptavidin tetramers. With a minimal set of interactions, we reproduce the formation of rectangular islands experimentally observed at pH ≥ 9.0. Specifically, we analyze two scenarios of the island growth. First, if streptavidin is rapidly adsorbed at t = 0 (stepwise coverage change without ongoing adsorption), the average linear island size is found to grow according to the Lifshitz–Slyozov law, R ∝ t1/3. Second, if the island growth occurs in parallel with streptavidin adsorption limited by diffusion in the solution, the Lifshitz–Slyozov law is also applicable, but only at the late stage, when the streptavidin coverage is appreciable. Proteins 2001;43:489–498. © 2001 Wiley‐Liss, Inc.