bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of the Thermal and Thermo‐Oxidative Degradation of a Polystyrene–Clay Nanocomposite
Authors: Vyazovkin Sergey , Dranca Ion , Fan Xiaowu , Advincula Rigoberto
Published: February 2004

Summary: Thermogravimetry and differential scanning calorimetry have been used to study the thermal and thermo‐oxidative degradation of polystyrene (PS) and a PS–clay nanocomposite. An advanced isoconversional method has been applied for kinetic analysis. Introduction of the clay phase increases the activation energy and affects the total heat of degradation, which suggests a change in the reaction mechanism. The obtained kinetic data permit a comparative assessment of the fire resistance of the studied materials.

The change in activation energy for the degradation of PS and the PS–clay nanocomposite with the extent of polymer conversion.

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The change in activation energy for the degradation of PS and the PS–clay nanocomposite with the extent of polymer conversion.
Cover Picture: Macromol. Rapid Commun. 2/2004
Authors: Kihara Hideyuki , Miura Toshiaki , Kishi Ryoichi
Published: February 2004

Cover: The picture on the cover shows SEM images of LC polymer films consisting of rotating fine fibers, which were prepared by photopolymerization‐induced phase separation under a cholesteric LC ordering field. The background images are polarizing optical micrographs of the fingerprint (left) and Grandjean (right) textures of the cholesteric phase that were used as the templates for preparation of the respective polymer films.

Details can be found in the Communication by H. Kihara,* T. Miura, and R. Kishi* on page 445.
Cover Picture: Macromol. Rapid Commun. 3/2004
Authors: Wang Wei , Fujiki Michiya , Nomura Kotohiro
Published: February 2004

Cover: Titanium complexes containing triaryloxoamine ligands of the type, TiX‐[(OArCH2)3N], exhibited notable catalytic activity for ethylene polymerization in the presence of MAO, especially at higher temperatures. The activity further increased upon the addition of a small amount of AIMe3, and dissociation of the one σ bond to generate the catalytically active species occurred.

Further details can be found in the Communication by W. Wang, M. Fujiki, and K. Nomura* on page 504.
Modeling Investigation of Hydrogel Volume Transition
Authors: Wu Shunnian , Li Hua , Chen J. Paul , Lam K. Y.
Published: February 2004

Summary: This paper provides an overview of the latest development in modeling and simulation of volume transition behaviors of hydrogels with models at both macroscopic and molecular levels. Energy conservation law, mass conservation law and momentum conservation law provide good starting points for developing models for hydrogel volume transition. Thermodynamic models, transport models, multiphasic mixture theory and molecular simulation are discussed. Thermodynamic models provide qualitative description of equilibrium volume transition of hydrogels. Both transport models and multiphasic mixture theory can predict transient and equilibrium volume transition of hydrogels. Molecular simulation provides mechanistic understanding of hydrogel volume transition. Several key parameters are summarized for future model development.
Binary Polymer Mixtures in Selective Solvents: Interfacial Structure
Authors: Abramchuk Sergei S. , Semenov Alexander N. , Khokhlov Alexei R.
Published: February 2004

Summary: The interaction of a large polymer droplet (formed by a poorly soluble polymer A) with a soluble polymer additive (polymer B) is investigated in the framework of a mean‐field approach. We found that polymer B may tend to adsorb on the surface of the droplet even when it is immiscible with polymer A in the droplet and is soluble in the solvent surrounding the droplet. We calculated the concentration profiles of both polymers A and B near the interface and established conditions for polymer B accumulation at the interface. The dependencies of the surface tension and the interfacial excess of polymer B on its bulk concentration are also calculated. We found that even a very small amount of homopolymer B additive may result in a significant reduction of the interfacial tension (by a factor of 2). The effect is stronger if the additive is more flexible than the insoluble polymer.

The region of parameters where B from dilute solution is adsorbed at the A/solvent interface (II).

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The region of parameters where B from dilute solution is adsorbed at the A/solvent interface (II).
Theoretical Study of the Effects of Templated Materials on Aggregate Formation
Authors: Chen Yong , Shew Chwen‐Yang , Gbemudu Chukwunonso , Chauhan Bhanu P. S.
Published: February 2004

Summary:We have conducted Monte Carlo simulations to investigate a greatly simplified model for a blend composed of templated materials (polymers or monomers), smaller reacting particles and solvents on a two‐dimensional lattice. In the simulations, we compute the mean chain conformation of flexible templated polymers, and the distribution of the number of adjacent reacting particles aligned along the same axis to rationalize how templated materials affect the physical aggregation of smaller particles in a blend. We first examine the effects of the effective interactions between templated materials and smaller reacting particles. For repulsive interactions, flexible templated polymers tend to contract to reduce repulsions arising from smaller reacting particles, but for attractive interactions, mean chain dimension increases to maximize attraction. When templated material composition is increased, the conformational deformation of templated polymers becomes more pronounced. Moreover, in the presence of attractive interactions, reacting particles are more dispersed in the blend. In contrast, repulsive interactions increase the probability of aggregation of reacting particles. Also, our findings show that templated monomers (without chain connectivity) interact with reacting particles more effectively than with templated polymers due to the greater interacting area per monomer, which enhances the dispersion and segregation of reacting particles in the blend due to the attractive and repulsive interaction, respectively. In addition, as templated material composition is increased, the probability of forming a larger aggregate decreases. This simple model allows us to elucidate the role of templated materials on the physical aggregation of smaller particles in a blend.

Probability distributionP(m) of findingmadjacent reacting particles along the same axis in the presence of templated polymers (open symbols) and templated monomers (solid symbols) for different monomer‐reacting particle ratio, 1:3 (□/▪), 1:1 (○/•) and 3:1 (▵/▴):.

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Probability distributionP(m) of findingmadjacent reacting particles along the same axis in the presence of templated polymers (open symbols) and templated monomers (solid symbols) for different monomer‐reacting particle ratio, 1:3 (□/▪), 1:1 (○/•) and 3:1 (▵/▴):.
Multi‐Objective Optimization of Semi‐Batch Copolymerization Reactors Using Adaptations of Genetic Algorithm
Authors: Nayak Arpan , Gupta Santosh K.
Published: February 2004

Summary: The polymerization of styrene‐acrylonitrile (SAN) random copolymers in semi‐batch reactors is optimized using multiple objective functions that are often conflicting and non‐commensurate in nature. These include the average composition of the copolymer product, its number‐average molecular weight, its polydispersity index, and the conversion of monomers attained in the reactor. Two decision/control variables are used, namely, the rate of continuous addition of a monomer‐solvent‐initiator mixture (having a specified and fixed composition) and the history of the temperature in the reactor. The elitist non‐dominated sorting genetic algorithm, NSGA‐II, is adapted and used for decision variables that are functions of time (trajectory optimization). This robust, AI (artificial intelligence)‐based technique, enables the solution of far more complex optimization problems than those reported in the literature. A set of several non‐dominating (equally good) Pareto optimal solutions was obtained. These provide insights into the conflicting nature of the objective functions. An engineer (decision maker) can then use his judgment (often intuitive) to choose the preferred solution from among these possibilities.

Pareto set of optimal solutions and some corresponding state variables for a Reference Problem.

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Pareto set of optimal solutions and some corresponding state variables for a Reference Problem.
Monte Carlo Simulations of Polymers in Nanoslits
Authors: Vacatello Michele
Published: February 2004

Summary:Monte Carlo computer simulations have been performed for model polymers confined in slits of thickness comparable to the transverse diameter of the chains. The density of polymer within the slits is allowed to vary with the slit thickness in such a way that the content of the slits is always in equilibrium with a large reservoir of bulk polymer. The calculations reveal the presence of polymer‐mediated attractive or repulsive interactions between the slit plates, oscillating with the slit thickness in good agreement with experimental results.

The base cell used in the simulations.

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The base cell used in the simulations.
Conformational Polymer Statistics from the Geometrical Scaling of Monomeric Units and the Characteristic Ratio from Circle Maps. Application to Carbohydrate Macromolecules
Authors: Mezzasalma Stefano A. , Angioletti Carmela , Cesàro Attilio
Published: February 2004

Summary: Basic results on conformational chain statistics were formerly derived from scaling concepts for geometry and a relativistic picture of Brownian self‐diffusion in liquids. A polymer conformation was interpreted as a geometrical scaling law of its monomer shape, where the concept of characteristic ratio identifies a mean metric coefficient, originating topologically from rotational degrees of freedom internal to single molecules. Here, we add the former theoretical results to first numerical calculations. They are performed for three polysaccharides, provided with different chain topologies and constrained conformationally to identical square‐well energy states with increasing width. The spatial coil dilation‐contraction has been described satisfactorily by dihedral sine‐like rotations on a circle at dimeric length scales. New intrinsic quantities, like inner characteristic ratio and angular Kuhn step, both belonging to the shape of single molecules, have been finally defined. The geometrical mechanism bringing them at larger scales, to point out the chain shape size, is still unknown and under consideration.

Conformational energy landscape of nigerose.

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Conformational energy landscape of nigerose.
Multiple Histogram Method and Static Monte Carlo Sampling
Authors: Inda Márcia A. , Frenkel Daan
Published: February 2004

Summary: We describe an approach to use multiple‐histogram methods in combination with static, biased Monte Carlo simulations. To illustrate this, we computed the force‐extension curve of an athermal polymer from multiple histograms constructed in a series of static Rosenbluth Monte Carlo simulations. From the complete histogram of the distribution function of the end‐to‐end vectors of the polymer chain, we can efficiently compute the polymer force‐extension curve.

Comparison of the stress‐strain curves for the stress ensemble (symbols) and the strain ensemble (lines). Results obtained for N = 100, 200, 400, and 600. For small x, f(x) = −F′(x) was computed by aproximating F(x) by a second degree polynomial and then taking the derivative. For large x, f(x) = −F′(x) was computed numerically.

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Comparison of the stress‐strain curves for the stress ensemble (symbols) and the strain ensemble (lines). Results obtained for N = 100, 200, 400, and 600. For small x, f(x) = −F′(x) was computed by aproximating F(x) by a second degree polynomial and then taking the derivative. For large x, f(x) = −F′(x) was computed numerically.
Cover Picture: Macromol. Theory Simul. 1/2004
Authors: Inda Márcia A. , Frenkel Daan
Published: February 2004

Cover: Histograms of the x‐coordinate of the end‐to‐end vector of an athermal polymer subject to an external force. Above: raw data – Rosenbluth sampling. Below (reflected(: improved histograms after applying the multiple histogram method.

Further details can be found in the Full Paper by M. A. Inda and D. Frenkel* on page 36.
Experimental study of thermal effects on the mechanical behaviour of a clay
Authors: Cekerevac Cane , Laloui Lyesse
Published: February 2004

The paper presents the results of an experimental study of thermal effects on the mechanical behaviour of a saturated clay. The study was performed on CM clay (Kaolin) using a temperature‐controlled triaxial apparatus. Applied temperatures were between 22 and 90°C. A comprehensive experimental program was carried out, including: (i) triaxial shear tests at ambient and high temperatures for different initial overconsolidation ratios; (ii) consolidation tests at ambient and high temperatures; and (iii) drained thermal heating for different initial overconsolidation ratios. The obtained results provide observations concerning a wide scope of the thermo‐mechanical behaviour of clays. Test results obtained at 90°C were compared with tests performed at ambient temperature. Based on these comparisons, thermal effects on a variety of features of behaviour are presented and discussed. Focus is made on: (i) induced thermal volume change during drained heating; (ii) experimental evidence of temperature influence on preconsolidation pressure and on compressibility index; (iii) thermal effects on shear strength and critical state; and (iv) thermal effects on elastic modulus. Thermal yielding is discussed and yield limit evolution with temperature is presented. The directions of the induced plastic strains are also discussed. Several remarks on the difference in the mechanical behaviour at ambient and high temperatures conclude the paper. Copyright © 2004 John Wiley & Sons, Ltd.
About Darcy's law in non‐Galilean frame
Authors: Geindreau C. , Sawicki E. , Auriault J.‐L. , Royer P.
Published: February 2004

This paper is aimed towards investigating the filtration law of an incompressible viscous Newtonian fluid through a rigid non‐inertial porous medium (e.g. a porous medium placed in a centrifuge basket). The filtration law is obtained by upscaling the flow equations at the pore scale. The upscaling technique is the homogenization method of multiple scale expansions which rigorously gives the macroscopic behaviour and the effective properties without any prerequisite on the form of the macroscopic equations. The derived filtration law is similar to Darcy's law, but the tensor of permeability presents the following remarkable properties: it depends upon the angular velocity of the porous matrix, it verifies Hall–Onsager's relationship and it is a non‐symmetric tensor. We thus deduce that, under rotation, an isotropic porous medium leads to a non‐isotropic effective permeability. In this paper, we present the results of numerical simulations of the flow through rotating porous media. This allows us to highlight the deviations of the flow due to Coriolis effects at both the microscopic scale (i.e. the pore scale), and the macroscopic scale (i.e. the sample scale). The above results confirm that for an isotropic medium, phenomenological laws already proposed in the literature fails at reproducing three‐dimensional Coriolis effects in all types of pores geometry. We show that Coriolis effects may lead to significant variations of the permeability measured during centrifuge tests when the inverse Ekman number Ek−1 is 𝒪(1). These variations are estimated to be less than 5% if Ek−1<0.2, which is the case of classical geotechnical centrifuge tests. We finally conclude by showing that available experimental data from tests carried out in centrifuges are not sufficient to determining the effective tensor of permeability of rotating porous media. Copyright © 2004 John Wiley & Sons, Ltd.
Comparison of non‐local and polar modelling of softening in hypoplasticity
Authors: Maier Th.
Published: February 2004

The paper deals with the comparison of a non‐local and a polar (Cosserat) hypoplastic model. The hypoplastic constitutive law in the version of von Wolffersdorff is chosen as local reference model. For the comparison the results of biaxial tests on dense Hostun Rf sand are predicted with both enhanced models. The comparison is based on a strict separation of input data from triaxial‐ and oedometer tests and output data from biaxial tests. The comparison is drawn in terms of the shear band width, the load–displacement curves and the influence of the pressure level. Finally, the non‐local and the polar hypoplastic model are applied on the strip foundation problem. Copyright © 2004 John Wiley & Sons, Ltd.
On the evolution of simple shear in saturated soils
Authors: Lu X. B. , Wang S.Y. , Peng Cui
Published: February 2004

Development of shear bands in saturated soils is a multi‐stage process based on the theoretical and numerical investigations in this paper. The soil is initially in homogenous shear strain state, and the instability can be characterized by a dimensionless number D. The inhomogenous distribution of shear strains appears when D>1, and the shear band will initiate and develop gradually. Numerical solutions show that only single shear band that is finally formed in the central region of the specimen even several disturbances (distributed along the specimen) appear in the beginning. Copyright © 2004 John Wiley & Sons, Ltd.
Functionalization of a poly(vinyl alcohol) in the solid state with a swelling agent by methacrylic anhydride
Authors: Becquart F. , Taha M. , Zerroukhi A. , Kaczun J. , Stebani U.
Published: February 2004

Poly(vinyl alcohol‐co‐vinyl acetate) was functionalized by methacrylic anhydride to introduce functional groups by a new process that consisted of modifying a polymer directly from a powder form in the solid state. To favor the diffusion of the reagents, a swelling agent composed by a mixture of ethylene carbonate and propylene carbonate was used. N‐methylimidazole was used as a basic catalyst of the esterification reaction, adjusting the reaction times. This work presents the process and the effects of the formulation on anhydride conversion. The side reactions were also determined; they all involved N‐methylimidazole. Decarboxylation reactions of the carbonates were characterized, that is, going from ethylene carbonate to ethylene glycol, which is able to react with two anhydride molecules by esterification reactions to, respectively, form 2‐hydroxyethyl 2‐methylpropenoate and ethyl 1,2‐bis(2‐methyl propenoate). The same side reactions are possible with propylene carbonate but are less reactive than the starting ethylene carbonate. Model anhydrides such as hexanoic and heptanoic anhydrides, less reactive than methacrylic anhydride, were used to characterize a new anhydride decarboxylation reaction. The homogeneity of the grafting is also discussed, especially its dependence on the polymer properties, the diffusion modes of the reagents (carbonate mixture and the anhydride), and the competition between the diffusional and chemical kinetics of methacrylic anhydride. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1618–1629, 2004
Novel dinitroxide mediating agent for stable free‐radical polymerization
Authors: Lizotte Jeremy R. , Anderson Sara G. , Long Timothy E.
Published: February 2004

A novel dinitroxide mediating agent that was suitable for stable free‐radical polymerization was synthesized and used in the block copolymerization of styrene and t‐butyl styrene. Quantitative yields of a novel dinitroxide based on 1,6‐hexamethylene diisocyanate and 4‐hydroxy‐2,2,6,6‐tetramethyl‐1‐piperidinyloxy were obtained. Various experimental parameters, including the nitroxide‐to‐initiator molar ratio, were examined, and it was determined that the polymerization was most controlled under conditions similar to those of conventional 2,2,6,6‐tetramethyl‐1‐piperidinyloxy‐mediated stable free‐radical polymerization. Moreover, the dinitroxide mediator proved to be a viable route for the facile two‐step synthesis of triblock copolymers of styrene and t‐butyl styrene. However, the dinitroxide mediation process resulted in a higher than expected level of nitroxide decomposition, which resulted in polymers possessing a terminal alkoxyamine and an adjacent hydroxylamine rather than a preferred internal bisalkoxyamine. This decomposition resulted in the formation of diblock copolymer species during the triblock copolymer synthesis. Gel permeation chromatography was used to monitor the chain‐end decomposition kinetics, and the determined observed rate constant (5.89 × 10−5 s−1) for decomposition agreed well with previous studies for other dinitroxide mediating agents. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1547–1556, 2004
Synthesis and characterization of naphthyl‐substituted poly(p‐phenylenevinylene)s with few structural defects for polymer light‐emitting diodes
Authors: Lee Nancy Hoi Sim , Chen Zhi‐Kuan , Huang Wei , Xu Yi‐She , Cao Yong
Published: February 2004

A series of naphthyl‐substituted poly(p‐phenylenevinylene)s (2N‐PPV, 4N‐PPV, and NAP‐PPV) has been synthesized and characterized by Fourier transform IR, 1H NMR, and elemental analysis. The polymers possess excellent solubility, high molecular weights, good thermal stability, and high photoluminescence efficiencies. Thermogravimetric analysis reveals the onset of degradation to be 347, 301, and 306 °C for 2N‐PPV, 4N‐PPV, and NAP‐PPV, respectively. The differential scanning calorimetry investigation gives the respective glass‐transition temperature values of 118, 135, and 141 °C. The UV and photoluminescence spectra measurements reveal that the polymers exhibit similar optical properties, indicating that side‐chain substitution has little effect on the optical properties of this series of polymers. Proton NMR measurement of the signal due to tolane–bisbenzyl defects at around 2.7 ppm indicates that all the polymers have negligible amounts of tolane–bisbenzyl defects along the polymer main chain as a result of the steric bulk imposed by the naphthalene side chain. The highest occupied and lowest unoccupied molecular orbital energy levels of the polymers are investigated through cyclic voltammetry. Polymer light‐emitting diodes utilizing the polymers as the emissive layer with a configuration of indium tin oxide/poly(3,4‐ethylenedioxythiophene)/polymer/Ba/Al are fabricated and evaluated. The diodes emit blue‐green to yellow‐green light with maximum peaks at 518, 542, and 486 nm for 2N‐PPV, 4N‐PPV, and NAP‐PPV, respectively. The respective turn‐on electric fields of the diodes are 0.84, 0.69, and 0.83 MV/cm and the respective maximum external quantum efficiencies are 0.08, 0.54, and 0.02%. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1647–1657, 2004
Studies of ethylene–styrene copolymerization with dinuclear constrained geometry complexes with methyl substitution at the five‐membered ring in indenyl of [Ti(η5:η1‐C9H5SiMe2NCMe3)]2 [CH2]n
Authors: Noh Seok Kyun , Lee Mijung , Kum Don Ho , Kim Kiseok , Lyoo Won Seok , Lee Dong‐Ho
Published: February 2004

The new dinuclear half‐sandwich CGC (constrained geometry catalyst) with methyl substitution in indenyl, [Ti(η5:η1‐2‐methylindenyl)SiMe2NCMe3]2 [(CH2)n] [n = 6 (10), n = 9 (11), n = 12 (12)], have been synthesized, and structure of these complexes has been characterized by 1H and 13C NMR. The most important feature is that two protons of methylene directly bonded to the indenyl ring become inequivalent to be shown as two separated resonances at 2.9 and 3.0 ppm, probably due to the formation of planar chirality caused by a titanium complex formation. It has been found that the dinuclear CGCs with methyl substitution at an indenyl ring were very active catalysts for ethylene and styrene copolymerization. The activity increases in the order of 10 < 11 < 12, which indicates that the presence of a longer bridge between two active sites contributes to facilitate the polymerization activity of the dinuclear CGC more effectively. This result might be understood by the implication that the steric factor rather than the electronic factor may play a major role to direct the polymerization behavior of the dinuclear CGC. It is found that the dinuclear catalysts are very efficient to incorporate styrene in the polyethylene backbone. The styrene contents in the formed copolymers ranged from 5 to 40% according to the polymerization conditions. One can observe strong signals at 29.7 ppm of the polyethylene sequences, and, in addition, peaks at 27.5, 36.9, and 46. 2ppm (Sβδ, Sαδ, and Tδδ, respectively) of sequences of EESEE. Weak peak at 25.3 ppm are attributed to Sββ, which represents SES sequence. The absence of a signal for Tββ at 41.3 ppm and for Sαα at 43.6 ppm shows there is no styrene–styrene sequences in copolymers. This result indicates that the dinuclear CGC are very effective to generate well‐distributed poly(ethylene‐co‐styrene)s. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1712–1723, 2004
Initiator‐fragment incorporation radical copolymerization of divinylbenzene and N‐isopropylacrylamide with dimethyl 2,2′‐azobisisobutyrate: Formation of soluble hyperbranched polymer nanoparticle
Authors: Sato Tsuneyuki , Higashida Naoki , Hirano Tomohiro , Seno Makiko
Published: February 2004

The copolymerization of divinylbenzene (DVB) and N‐isopropylacrylamide (NIPAm) with dimethyl 2,2′‐azobisisobutyrate of a concentration as high as 0.50 mol/L proceeded homogeneously without any gelation at 80 °C in N,N‐dimethylformamide, where the concentrations of DVB and NIPAm were 0.15 and 0.50 mol/L. The copolymer yield increased with time and leveled off over 50 min. Although DVB was consumed more rapidly than NIPAm, both comonomers were completely consumed in 50 min. The homogeneous polymerization system at 80 °C involved electron spin resonance‐observable propagating polymer radicals, the total concentration of which increased with time. The resulting copolymer was soluble in tetrahydrofuran, chloroform, acetone, ethyl acetate, acetonitrile, N,N‐dimethylformamide, dimethyl sulfoxide, and methanol, but insoluble in benzene, n‐hexane, and water. The copolymer showed an upper critical solution temperature (50 °C on cooling) in a methanol–water [11:3 (v/v)] mixture. Dimethyl 2,2′‐azobisisobutyrate fragments as high as 37–45 mol % were incorporated as terminal groups in the copolymers through initiation and primary radical termination. The contents of DVB and NIPAm were 10–30 mol % and 30–50 mol %, respectively. The intrinsic viscosity of the copolymer was very low (0.09 dL/g) at 30 °C in tetrahydrofuran despite high weight‐average molecular weight (1.2 × l06 by multi‐angle laser light scattering). These results indicate that the copolymer was of hyperbranched structure. By transmission electron microscopy observation, the individual copolymer molecules were visualized as nanoparticle of 6–20 nm. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1609–1617, 2004
Polysiloxanes with chlorobenzyl groups as precursors of new organic‐silicone materials
Authors: Kazmierski K. , Hurduc N. , Sauvet G. , Chojnowski J.
Published: February 2004

Various polysiloxanes bearing chlorobenzyl side groups were synthesized by the hydrolytic polycondensation of the 73:27 mol/mol mixture of [2‐(4‐chloromethylphenyl)ethyl] methyldichlorosilane and [1‐(4‐chloromethylphenyl)ethyl] methyldichlorosilane followed by the cationic equilibration or coequilibration with octamethylcyclotetrasiloxane, D4. 1,3‐Divinyltetramethyl‐disiloxane was used as the chain end blocker to obtain a vinyl–Si ended chlorobenzyl‐substituted polysiloxane. In some cases, the polymer was additionally treated with dimethylvinylchlorosilane to achieve full substitution of chain ends by the vinyl group. Cohydrolysis of the chlorobenzylic monomer mixture with dimethyldichlorosilane was also practiced. Multiblock copolymers were obtained by polyhydrosilylation of the α,ω‐divinylsilyl chlorobenzyl‐substituted polysiloxanes with α,ω‐dihydrosilyl polydimethylsiloxanes. All these polymers and copolymers containing reactive chlorobenzylic groups were demonstrated to be convenient precursors of functional polysiloxanes of potential practical use. Some specific functional groups, such as quaternary ammonium salt groups of biocidal activity or azobenzene groups making the polymer sensitive to external stimuli by light, may be readily generated on polysiloxane under mild conditions. The chlorobenzylic substituted polysiloxanes may be also used as macroinitiators of the atom transfer radical polymerization, to obtain polysiloxanes with grafted organic polymers, such as styrene, 4‐chloromethylstyrene, and n‐butylacrylate. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1682–1692, 2004
Influence of phenylenediamine additions on the morphology and on the catalytic effect of polyaniline
Authors: Duić Ljerka , Kraljić Marijana , Grigić Sanja
Published: February 2004

The influence of para‐, ortho‐, and meta‐phenylenediamine (p‐, o‐, and m‐PDA) additions on the electrochemical synthesis of polyaniline has been investigated by the use of cyclic voltametry. It has been found that small additions (1 and 5 mmol L−1) of PDA monomers influence significantly the polymerization rate. Whereas p‐PDA increases the polymerization rate, the addition of o‐ or m‐PDA slows it down. Therefore, a different number of potential cycling is necessary to obtain similar thickness of layers. The layers exhibit very different morphology, which changes from “spaghetti‐like” for polyaniline to “sponge‐like” for p‐PDA, to “pebble‐like” for o‐PDA and to “cauliflower‐like” for m‐PDA additions, respectively. The catalytic effect of the synthesized polymer layers has been tested. It has been found that all the layers exhibit catalytic effect in lowering the redox potential of hydroquinone/quinone tested reaction, but the rate of the electrocatalytic reaction varies depending on the PDA monomer added. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1599–1608, 2004
Aqueous solution properties of pH‐responsive AB diblock acrylamido–styrenic copolymers synthesized via aqueous reversible addition–fragmentation chain transfer
Authors: Sumerlin Brent S. , Lowe Andrew B. , Thomas David B. , Convertine Anthony J. , Donovan Michael S. , McCormick Charles L.
Published: February 2004

Here we report the synthesis and solution characterization of a novel series of AB diblock copolymers with neutral, water‐soluble A blocks consisting of N,N‐dimethylacrylamide and pH‐responsive B blocks of N,N‐dimethylvinylbenzylamine. To our knowledge, this represents the first example of an acrylamido–styrenic block copolymer prepared directly in a homogeneous aqueous solution. The best blocking order [with poly(N,N‐dimethylacrylamide) as a macro‐chain‐transfer agent] yielded well‐defined block copolymers with minimal homopolymer impurities. The reversible aggregation of these block copolymers in aqueous media was studied with 1H NMR spectroscopy and dynamic light scattering. Finally, an example of core‐crosslinked micelles was demonstrated by the addition of a difunctional crosslinking agent to a micellar solution of the parent block copolymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1724–1734, 2004
Poly(ethylene terephthalate) modified with aromatic bisester diamides: Thermal and oxygen barrier properties
Authors: Hibbs Michael R. , Holtzclaw Jeremy , Collard David M. , Liu Richard Y. F. , Hiltner Anne , Baer Eric , Schiraldi David A.
Published: February 2004

The synthesis and properties of poly(ethylene terephthalate) (PET) copolymers containing four bisester diamide structural units are reported. Two of the bisester diamides consist of three para‐substituted aromatic rings, and the other two consist of three meta‐substituted aromatic rings. The copolymers have been characterized by nuclear magnetic resonance, differential scanning calorimetry, and dilute solution viscometry. Three of the copolymers can be compression‐molded into amorphous films for oxygen barrier testing, and one of these three films can be oriented for additional barrier testing. The three amorphous films all have lower permeabilities than unoriented PET. However, this difference diminishes upon the orientation of the polymer films. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1668–1681, 2004
Synthesis and characterization of negative‐type photosensitive hyperbranched polyimides with excellent organosolubility from an A2 + B3 monomer system
Authors: Chen Huan , Yin Jie
Published: February 2004

A series of photosensitive hyperbranched polyimides (HB‐PIs) were prepared through facile end‐group modifications of the fully imidized polymer. A triamine, 1,3,5‐tris(4‐aminophenoxy)benzene, and a dianhydride, 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride, were condensed with a dropwise addition method in a molar ratio of 1/2 to afford an anhydride‐terminated poly(amic acid) precursor, which was then end‐capped by 4‐aminophenol and chemically imidized to yield a phenol‐terminated HB‐PI. The modifications of the terminal phenol groups of the polyimide by acyl chloride compounds (acryloyl chloride, methylacryloyl chloride, and cinnamoyl chloride) gave the target polymers. The photosensitive HB‐PIs showed good thermal properties and excellent solubility even in low‐boiling‐point solvents at room temperature, such as acetone, 1,1,2‐trichloroethane, tetrahydrofuran, and chloroform. Photosensitive property studies revealed good photolithographic properties with a resolution greater than 3 μm and a sensitivity of 650–680 mJ/cm2. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1735–1744, 2004
Pyrrole derivatives for electrochemical coating of metallic medical devices
Authors: Weiss Zehava , Mandler Daniel , Shustak Galit , Domb Abraham J.
Published: February 2004

Electropolymerization of medical devices such as cardiovascular stents may posses advantages including a simple and reproducible process with the ability to control the thickness, adherence, and composition of the coating by the duration and intensity of the applied current, the monomer composition and concentration, the solvent, and the reaction conditions. The properties of the polymer can also be controlled by copolymerization of different monomers, grafting substituents to a functionalized polymer, and by entrapping biomolecules. This article describes the synthesis of a range of pyrrole‐based monomers and their electrocoating onto stainless steel surfaces. N‐substituted pyrrole monomers with C1–C18 alkyl chains and poly (ethylene glycol) chains were synthesized in good yields and purity. Electropolymerization of these monomers provided uniform coatings with different hydrophobicities. Studies now focus on the incorporation of drugs in the coated device for release from the surface. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1658–1667, 2004
Reaction of oligoalcohols with diepoxides: An easy, one‐pot way to star‐shaped, multibranched polymers. II. Poly(ethylene oxide) stars—synthesis and analysis by size exclusion chromatography triple‐detection method
Authors: Lapienis Grzegorz , Penczek Stanislaw
Published: February 2004

An Erratum has been published for this article in Journal of Polymer Science Part A: Polymer Chemistry (2004) 42(10) 2575‐2576

Starlike, highly branched (AxByAz) macromolecules having from a few to 100 arms and molar masses up to 105 were prepared in three stages with the one‐pot, arms‐core‐arms method (By stands for y molcules of former diepoxides introduced into the core). Oligoalcohols, at least partially converted into their alcoholate counterpart states, reacted with diepoxy compounds giving star‐shaped, highly branched macromolecules. With the properly chosen conditions, complete conversion of both starting components was achieved. In this article homostars built with the first and second generation of poly(ethylene oxide) arms (Ax and Az, respectively) are described. The number of arms (f) was determined either by direct measurements of the number‐average molcular weight (Mn) of the first and second stars (Mn of arms Ax and Az is known) or by calculating f from branching indices g and g′ determined from the radius of gyration and the limited viscosity number measured with size exclusion chromatography (SEC) triple detection with TriSEC software. For a few samples, Mn was measured with high‐speed membrane osmometry. The progress of the stars' formation was monitored by 1H NMR, SEC, and matrix‐assisted laser desorption/ionization time‐of‐flight methods. Functionalization of the OH end groups in the second generation of arms was observed by 1H and/or 31P NMR. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1576–1598, 2004
Linear polyamides from L‐malic acid and alkanediamines
Authors: Regaño Celia , Alla Abdellilah , de Ilarduya Antxon Martínez , Muñoz‐Guerra Sebastián
Published: February 2004

A series of linear polyamides (PnMLM) derived from O‐methyl‐protected L‐malic acid and 1,n‐alkanediamines with even n values ranging from 4 to 12 were prepared and fully characterized. L‐Malic acid entered in the chain with a random orientation rendering essentially aregic polymers. PnMLM displayed optical rotation consistent with the content of the polymer in malic units, and they all were crystalline with melting points ranging from 158 to 188 °C and glass‐transition temperatures varying from 37 to 70 °C. PnMLM appeared to be fairly stable to heat with thermal decomposition starting close to 300 °C. Hydrolytic degradation of PnMLM at 37 °C was slow, but the process was significantly faster at 70 °C. Thermal degradation took place with the formation of cyclic malimides in the residual polymer and released the 1,n‐alkanediamine. However, hydrolytic degradation took place in a first stage with the formation of open chains of carboxylic‐ and amine‐ended oligomers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1566–1575, 2004
Radical polymerization of allylbiguanide
Authors: Iio Kokoro , Yamasaki Susumu , Tasaki Shinji , Kudoh Hisako , Matsunaga Mutsuo
Published: February 2004

Monoallyl compounds are not readily homopolymerized by a conventional free‐radical mechanism. However, we successfully performed the radical polymerization of allylbiguanide hydrochloride in a concentrated acid solution (hydrochloric acid or phosphoric acid) in the presence of a radical initiator at 50 °C. The polymer product was precipitated from the reaction solution through the addition of an excess amount of acetone. The precipitated crude polymer [polyallylbiguanide (PAB)] was then purified by dialysis. PAB was confirmed by elemental analysis, infrared spectroscopy, and 1H NMR. The molecular weight range of PAB was 10,340–113,200, and PAB exhibited a low polydispersity (weight‐average molecular weight/number‐average molecular weight = 1.04–1.68) by multi‐angle laser light scattering. The polymerization of allylbiguanide was quite sensitive to the protonic concentration of the inorganic acid. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1707–1711, 2004
Theoretical study of the free‐radical copolymerization of styrene with methyl methacrylate: Comparative study to the styrene–acrylonitrile monomer system
Authors: Cieplak Piotr , Kaim Andrzej
Published: February 2004

Enthalpic and electronic terminal and penultimate unit effects in the free‐radical copolymerization of styrene (S) with methyl methacrylate (M) were investigated by quantum mechanical calculations at 0 and 298 K. Total energies, zero‐point energies scaled by a 0.96 factor, and thermal enthalpy corrections for all optimized structures were computed at the B3‐LYP/6‐31G(d) level of theory. Differences in enthalpies for elementary propagation reactions at 0 and 298 K did not exceed 0.6 kcal/mol. Enthalpic effects of the replacement of S by M in the penultimate position of the growing radicals in elementary copolymerization propagation reactions (enthalpic penultimate unit effects) were always positive, ranging from 1.2 to 3.3 kcal/mol at 298 K. The values suggested that the elementary propagation reactions involving more S units in the growing polymer chain ends should be slightly thermodynamically preferred. A comparison of these results with those for the S–acrylonitrile monomer system showed that the most crucial feature differentiating enthalpic effects for the two monomer systems is the replacement of M by acrylonitrile in the reaction pair CH3‐S‐M · + M → CH3‐S‐M‐M · and CH3‐M‐M · + M → CH3‐M‐M‐M ·. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1557–1565, 2004
Thiol‐ene photopolymerization of polymer‐derived ceramic precursors
Authors: Cramer Neil B. , Reddy Sirish K. , Lu Hui , Cross Tsali , Raj Rishi , Bowman Christopher N.
Published: February 2004

The liquid, ceramic precursor monomer VL20 was copolymerized with a thiol monomer in a traditional radical thiol‐ene photopolymerization. Polymerization occurred via addition of the thiol functional group to the vinyl silazane functional group in a 1:1 ratio consistent with a step‐growth polymerization. Gelation occurred at a high conversion of functional groups (70%) consistent with an average molecular weight and functionality of 560 and 1.7, respectively, for VL20 monomers. Initiatorless photopolymerization of the thiol‐VL20 system also occurred upon irradiation at either 365 or 254 nm. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1752–1757, 2004
Photoinduced cationic ring‐opening frontal polymerizations of oxetanes and oxiranes
Authors: Crivello J. V. , Falk B. , Zonca M. R.
Published: February 2004

The photoinitiated cationic ring‐opening polymerizations of certain epoxides and 3,3‐disubstituted oxetanes display the characteristics of frontal polymerizations. When irradiated with UV light, these monomers display a marked induction period, during which little conversion of the monomer to the polymer takes place. The local application of heat to an irradiated monomer sample results in polymerization that occurs as a front propagating rapidly throughout the entire reaction mass. For the characterization of these frontal polymerizations, the use of a new monitoring technique, employing optical pyrometry, has been instituted. This method provides a simple, rapid means of following these fast polymerizations and quantitatively determining their frontal velocities. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1630–1646, 2004
Synthesis and sulfonation of poly(arylene ether)s containing tetraphenyl methane moieties
Authors: Wang L. , Meng Y. Z. , Wang S. J. , Hay A. S.
Published: February 2004

Novel poly(arylene ether)s with sulfonic acid containing pendent groups were successfully synthesized by the nucleophilic displacement of aromatic dihalides with bisphenols in an aprotic solvent in the presence of excess potassium carbonate followed by sulfonation with chlorosulfonic acid. The sulfonation took place only at the controlled positions on the phenyl rings due to the novel bisphenol structures designed. The sulfonic acid group containing polymers were very soluble in common organic solvents, such as dimethyl sulfoxide, N,N′‐dimethylacetamide, and dimethylformamide, but swelled only slightly in water. These sulfonic acid group containing polymers were readily cast into tough and smooth films from organic solvents. The synthesized polymers had high glass‐transition temperatures of 171.0–240.7 °C and high molecular weights of 15,600–33,000 Da. These films could potentially be used as proton‐exchange membranes for fuel cells. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1779–1788, 2004
Synthesis and characterization of original functional polymers of tetrafluoroethylene and 4,5,5‐trifluoro‐4‐ene pentyl acetate
Authors: Kostov George , Améduri Bruno , Boutevin Bernard , Bauduin Gérard , Stankova Maya
Published: February 2004

The bulk radical copolymerization of tetrafluoroethylene (TFE) with 4,5,5‐trifluoro‐4‐ene pentyl acetate (FAc), initiated by tert‐butyl peroxypivalate to synthesize original, functionalized fluorinated poly(TFE‐co‐FAc), was investigated. FAc monomer was prepared from a five‐step process. The copolymerization was carried out in batch at different initial monomer molar ratios ([TFE]o/[FAc]o ranging from 95/5 to 10/90 mol %) and at different initiator concentrations (ranging between 0.075 and 1.100 mol % about the monomers) at 70 °C. All the experiments revealed the production of fluorooligomers as evidenced by an allylic‐transfer reaction from FAc. The microstructure of these copolymers (i.e., the molar percentage of both monomers in the copolymers) was assessed by 19F NMR spectroscopy. From the kinetics of copolymerization, two key characteristics were determined. First, the reaction order to the initiator (being 1.07) and that of FAc monomer (0.85) showed a heterogeneous character of the copolymerization and monomolecular chain‐transfer reaction to FAc. Second, from the Tidwell and Mortimer method, the reactivity ratios of both comonomers were determined, showing a tendency to alternance in a wide range of initial monomeric ratios (30/70–70/30): rFAc = 0.20 ± 0.26 and rTFE = 0.18 ± 0.15. Alfrey and Price's Q and e values of FAc were calculated by Greenley's technique [QFAc = 0.098 (from QTFE = 0.032) and eFAc = 1.23 (vs eTFE = 1.63)], indicating that FAc is a strong electron‐withdrawing monomer as TFE. The normalized monomer‐diad and triad fractions as a function of the polymer composition were obtained from the comonomer sequence‐distribution procedure. The average molecular weights and molecular weight distributions as well as the thermal properties (glass‐transition temperature and decomposition temperature) of the fluorocopolymers were assessed and are discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1693–1706, 2004
Synthesis of polystyrene–poly(tert‐butyl methacrylate)–poly(ethylene oxide) triarm star block copolymers
Authors: Nasser‐Eddine Mohamad , Reutenauer Simone , Delaite Christelle , Hurtrez Guy , Dumas Philippe
Published: February 2004

Three alternative routes, using the heterobifunctional macroinitiator technique, have been developed to obtain polystyrene–poly(tert‐butyl methacrylate)–poly(ethylene oxide) triarm star block copolymers. Only the route showing the reverse initiation of tert‐butyl methacrylate on potassium alkoxide leads to the pure star, whereas the other strategies lead to incomplete initiation because of either an increase in the side reactions, such as transesterification, or a decrease in the accessibility toward bulky catalysts. These limits are linked to the particular location of the initiating group at the junction of the two blocks of the copolymer precursor. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1745–1751, 2004