bluuebunny/crossref_metadata_2025 huggingface dataset:
Sorption and addition of bromine from aqueous solutions on cis‐1,4‐polyisoprene
Authors: Lewin Menachem , Penhasi Adel
Published: April 2003

The sorption of bromine from bromine water on cis‐1,4‐polyisoprene film and the initial stages of bromination are studied at concentrations of 0.002–0.1 mol/l and temperatures of 15–35°C. The diffusion coefficient of bromine into natural rubber (NR) is 1.3–2.0 × 10−6 cm2/sec for the total sorption and 5–13 × 10−7 cm2/sec for the irreversible sorption. The partition coefficient of bromine between water and rubber increased from 17.3 at 15°C to 37.1 l/kg at 35°C. The chemical potential, enthalpy and change in entropy of partition are, at 25°C, respectively: −1.9 kcal/mol, 6.6 kcal/mol and 28.4 cal/mol. K. The irreversible sorption is due to a charge‐transfer complex between bromine molecules and double bonds of the rubber. The complex is the first stage of the addition reaction, which becomes noticeable at concentrations above 0.012 mol/l. With increasing bromine concentration the concentration of the complex decreases and the added bromine increases. The charge transfer complex appears to change the conformation of the cis‐NR chains so that the bromine addition occurs in the trans‐conformation, as shown by FT–IR spectra. The bromination is accompanied by a marked crystallization effect as illustrated by thermal analysis and WAXS measurements.
Kinetic behavior of UV‐sensitive polymers from modified natural rubber
Authors: Visconte Leila L. Y. , Andrade Cristina T. , Azuma Chiaki
Published: April 2003

Photosensitive copolymers have been obtained by chemical modification of natural rubber. The introduction of the photoreactive cinnamoyl group in different conversions has been carried out by the reaction of natural polyisoprene with maleic anhydride, followed by ring opening and condensation with some oxyalkylcinnamate esters. These reactions gave rise to five polymer series. Each series, for which the anhydride content was kept constant, is constituted of five copolymeric products, differing from each other in the size of the aliphatic chain between the chromophore and the main chain. The photosensitive products were submitted to UV irradiation, and their kinetic behavior has been investigated in order to correlate structural dissimilarities with the dimerization rate constants.
Photosensitive poly(vinyl alcohol) bearing N‐(1‐pyridinio)benzamidate groups
Authors: Nagasawa Jun'ichi , Tamaki Takashi , Ichimura Kunihiro
Published: April 2003

Poly(vinyl alcohol) (PVA) bearing N‐(1‐pyridinio)benzamidate (PB) was synthesized through acetalization of PVA and 4‐dimethoxymethyl‐N‐(1‐pyridinio)benzamidate (DMPB) in water. The PB groups in PVA–PB had almost the same proportion of DMPB to the starting PVA. The UV spectrum of PVA–PB shows an absorption band of pyridinium ylide as a shoulder around 300 nm in water, and as a maximum at 315 nm in a film on a quartz plate. These absorption bands decreased on irradiation at 313 nm. The photoreaction of the PVA–PB film proceeds much faster than that of PVA–PB in water. The solution, of PVA‐bearing high‐PB content, became slightly turbid during irradiation. After irradiation the film became insoluble in water, and the soluble fraction of polymer (P̄ = 1700) was 3% at a PB content of 1 mol% and less than 1% at that of more than 2 mol%. This polymer can be applied as a water‐soluble negative photoresist.
Kinetic study of cyanoguanidine resin formation: acid hydrolysis of hydroxymethyl and methoxymethyl cyanoguanidine
Authors: Shiba R. , Takahashi M.
Published: April 2003

The hydrolysis of hydroxymethyl cyanoguanidine and methoxymethyl cyanoguianidine in acidic aqueous media were studied by analyzing the eluted formaldehyde and the reaction products. Dihydroxymethyl cyanoguanidine released two formaldehydes with different rates because one of the two hydroxymethyl groups is intramolecularly interactive through the hydrogen bond. Methanol dissociation from methoxymethyl cyanoguanidine was seven to eight times faster than the dissociation of hydroxymethyl group, and the overall hydrolysis kinetics were similar to those of hydroxymethyl cyanoguanidine.
Complexation of poly(ethylene glycol) with some salts of alkali‐earth metals
Authors: Bekturov Esen , Tolendina Akmaral , Shaikhutdinov Yerenqaip , Dzhumadilov Talkybek
Published: April 2003

The interaction of poly(ethylene glycol) with some salts of alkali‐earth metals (Mg(ClO4)2, BaCl2, SrCl2, SrBr2 and CaCl2) in methanolic solutions was investigated by electroconductivity, viscometry, X‐ray diffractometry and NMR. It was established that the conformation of macromolecules is strongly changed in the presence of Mg(ClO4)2. Chlorides and bromides of alkali‐earth metals have a weak influence on macromolecule size. The formation of amorphous complexes in the PEG–Mg(ClO4)2 system and crystalline complexes in PEG–chloride systems of alkali‐earth metals was shown.
Polymer role in advanced battery technology
Authors: Wada Moriyasu
Published: April 2003

A brief introduction to a new generation of sealed, rechargeable battery, a nickel metal hydride battery (Ni‐MH), is presented in connection with the polymer role in battery technology and engineering.

Ni‐MH batteries have higher energy density and better environmental friendliness than the conventional sealed nickel cadmium (Ni‐Cd) batteries, and accordingly the importance of the battery is increasing in the area of high‐technology information, communication and audiovideo equipment.

In this article it is pointed out that the key technologies for Ni‐MH batteries are: tridimensional nickel foam or mat for the positive nickel electrode substrate made by nickel plating of polyurethane foam or polyester nonwoven fabric; hydrogen‐storage negative electrode treated with hydrophobic polymer; and modified polypropylene nonwoven fabric separator with permanent hydrophilic properties.

Moreover, the further importance of polymer science and technology to improve Ni‐MH battery performance is described.
Gas separation using polymer membranes: an overview
Authors: Ghosal Kanchan , Freeman Benny D.
Published: April 2003

This overview article discusses fundamental principles of gas sorption and transport in rubbery and glassy polymers and material selection guidelines for gas separation membranes. Comparisons between the performance of membrane‐based gas separation systems and more conventional technologies in key commercial applications are provided. Companion articles in this special edition focus on state‐of‐the‐art reviews and descriptions of theoretical and experimental developments important in the technology of gas separations using polymeric membranes.
Molecular modeling studies of polymeric gas separation and barrier materials: structure and transport mechanisms
Authors: Jacobson Solomon H.
Published: April 2003

Molecular modeling studies have been completed on cis‐PTBA(poly(tert‐butylacetylene)) and Sixef44 polyimide, two glassy polymers that can be used to form gas separation membranes. The modeling studies show that polymer backbone bond rotations in PTBA are not thermally allowed. This leads to a helical structure for the cis‐PTBA chains which pack as if the helices were rigid rods. Here, polymer free volume is formed by the interstitial space between adjacent helices, and gas transport occurs via continuous diffusion through the resulting channel‐like free volume. On the other hand, Sixef44 exhibits a flexible polymer backbone, which leads to the formation of irregular voids. In this case, gas molecules are free to move within the voids, but transport occurs only by hopping to an adjacent void, or by void diffusion. In either case, gas transport is closely coupled to polymer backbone motion. Thus, these studies suggest two different types of free volume and gas transport mechanisms. The diffusion mechanism in glassy polymer membranes will depend on the nature of the free volume (e.g. the type of chain packing), and the polymer backbone chain flexibility.
Morphology and thermomechanical properties of latex films
Authors: Gauthier Catherine , Perez Jo
Published: April 2003

Latex films involve polymers, copolymers and (or) polymer blends, with more or less complex morphologies. First of all, the mechanical behavior of their amorphous polymeric component is considered. A theoretical approach, which relates macroscopic behavior to molecular processes, is used to model its dynamic mechanical properties and also plastic behavior. Then, in the case of heterogeneous films, we propose that information about the morphology of samples can be deduced from a comparison of their measured viscoelastic properties with the corresponding properties calculated for a suitable model. After a brief review of the theoretical approaches for the mechanical behavior of multiphase systems, we show the validity of the procedure in the case of latex films obtained from different copolymerization pathways. Thus, it is possible (a) to get information about the morphology of binary systems, (b) to determine the stability of the morphology, and (c) to characterize a third phase as an interphase between nodules and matrix. High stress–strain behavior is discussed in the case of latex films reinforced with nanoparticles of silica or with cellulose whiskers.
Relationship between structure and rheological properties in the melt of polymers containing spherical inclusions
Authors: Bardollet P. , Bousmina M. , Muller R.
Published: April 2003

The linear viscoelastic behavior of model rubbertoughened polymer melts has been studied. The most significant influence of the dispersed crosslinked rubber phase on the melt rheology of the blends is the existence of a secondary plateau for the storage modulus G′ at low frequencies. This behavior was ascribed to a percolation phenomenon, leading to the formation of a threedimensional network of inclusions, and contributing to the elasticity at low frequencies of the blend. Two different systems were investigated: (a) a polystyrene matrix with crosslinked and structured latex particles and (b) silicon oil matrices with homogeneous crosslinked PMMA particles. An initial shearing history was found to influence the dynamic mechanical properties of the molten blends and in particular to lower the lowfrequency plateau value for G′. During a subsequent annealing, the plateau modulus increases again. These results are in agreement with the assumption of a particle network.
Synthesis and properties of urethane elastomer‐modified epoxy resin having hydroxymethyl group
Authors: Ohtsuka Keiko , Hasegawa Kiichi , Fukuda Akinori
Published: April 2003

Synthesis and properties of urethane elastomer‐modified epoxy resins were studied. The urethane elastomer‐modified epoxy resins were synthesized by the reaction of a 4‐cresol type epoxy compound having hydroxymethyl groups (EPCDA) with isocyanate prepolymer. The structure was identified by IR, 1H NMR and GPC. These epoxy resins (EPCDATDI) were mixed with a commercial epoxy resin (DGEBA) in various ratios. The mixed epoxy resins were cured with a mixture of 4,4′‐diaminodiphenylmethane and 3‐phenylenediamine (molar ratio 6:4) as a hardener. The curing behaviour of these epoxy resins was studied by DSC. The higher the concentration of EPCDATDI, the higher the onset temperature and the smaller the rate constant (k) of the exothermic cure reaction were. It was considered that the ratio of hydroxymethyl group to epoxide group was very small and the molecular weight of EPCDATDI was large. Therefore, the accelerating effect of the hydroxymethyl group on the epoxide–amine reaction was cancelled by the retardant effect of increased molecular weight and viscosity, and decreased molecular motion. Toughness was estimated by Izod impact strength and fracture toughness (K1C). On addition of 10 wt% EPCDATDI with low molecular weight (M̄n 6710, estimated by GPC using polystyrene standard samples), Izod impact strength and K1C increased by 70% and 60%, respectively, compared with unmodified epoxy resin. Glass transition temperatures (Tg) for the cured epoxy resins mixed with EPCDATDI measured by dynamic mechanical spectrometry were the same as those of unmodified epoxy resin. The storage modulus (E′) at room temperature decreased with increasing concentration of EPCDATDI. Toughness and dynamic mechnical behaviour of cured epoxy resin systems were studied based on the morphology.
Stereoregularity in poly[methyl(3,3,3‐trifluoropropyl)siloxane]
Authors: Kuo Chung‐Mien , Saam John C. , Taylor Richard B.
Published: April 2003

Anionic ring‐opening polymerization of the cis and trans isomers of 1,3,5‐trimethyl‐1,3,5‐tris(3′,3′,3′‐trifluoropropyl)cyclotrisiloxane (cis‐ and trans‐F3) and their mixtures was conducted under conditions that suppressed siloxane bond redistribution in order to preserve stereoregularity formed in the resulting poly[methyl(3,3,3‐trifluoropropyl)siloxane] (PMTFPS). Proton decoupled 19F NMR of the resulting polymers was interpreted by assuming that the original stereoconfiguration of the monomer was preserved and that the monomer inserted with a roughly equal probability of forming meso or racemic configurations relative to the configuration of the reacting chain end. Polymers from cis‐F3 were solid and crystalline at room temperature while the more typical polymers from mixtures of isomers containing greater than 50% trans‐F3 were liquid and amorphous.
Poly(2,2‐dimethyltrimethylene carbonate)‐block‐poly(dimethylsiloxane)‐block‐poly(2,2‐dimethyltrimethylene carbonate). Synthesis and thermal properties
Authors: Müller Achim J. , Keul Helmut , Höcker Hartwing
Published: April 2003

Lithium salts of hydroxytelechelic poly(dimethylsiloxane) [poly‐(DMS)] were used as initiators for the anionic ring‐opening polymerization of 2,2‐dimethyltrimethylene carbonate (DTC). Triblock copolymers were obtained in high yields. Complexation of the active site in DTC polymerization by the poly(DMS) chain leads to a decrease in polymerization rate. The thermal properties of the copolymers of different compositions were determined. Catalysed thermal degradation of the block copolymers leads to cyclic oligomers Dn and DTC upon ring‐closing depolymerization.
Some light on the concept of unreactivity arising from active center association in anionic polymerizations
Authors: Young R. N. , Fetters L. J. , Huang J. S. , Krishnamoorti R.
Published: April 2003

A long held assumption in hydrocarbon based anionic polymerization involving organolithiums is that the aggregated species are unreactive and thus serve only as reservoirs from which the active singlet species momentarily emerge to participate in the initiation or propagation events. This work demonstrates that contrary to the notion of aggregate dormancy such species can participate in monomer addition. The approach involved freeze‐dried vitrified polystyryllithium which was found to be reactive toward butadiene and methanol vapors. The sub‐glass transition state of the polystyryllithium eliminates the establishment of the aggregate: singlet equilibrium as a result of the inability of chains to undergo diffusion. Furthermore, it is shown that the lower bound gradient for the dependence of propagation rate on active center concentration, within experimental error, is about 1/5 for the majority of those diene systems where the active center concentration covers at least two decades. A computer evaluation of the propagation rate: active center data was done with the aim of testing and determining the equilibrium constants of these aggregated systems.
Synthesis and properties of fluorinated polyimides and fluorinated poly(imide amide)s containing pendent cyano groups
Authors: Mercer Frank W. , McKenzie Martin T. , Bruma Maria , Schulz Burkhard
Published: April 2003

A series of fluorinated polyimides and fluorinated poly(imide amide)s containing pendent cyano groups were prepared and investigated to determine their dielectric constants as a function of relative humidity and thermal characteristics. The fluorinated polymides and fluorinated poly(imide amide)s containing pendent cyano groups were prepared by reaction of bis(4‐aminophenoxy) benzonitriles with a fluorinated dianhydride and with a fluorinated di(acid chloride) containing preformed imide rings. The properties of the fluorinated polyimides and fluorinated poly(imide amide)s containing pendent cyano groups were compared with those of fluorinated polyimides and fluorinated poly(imide amide)s prepared from 1,3‐bis(4‐aminophenoxy)benzene. The introduction of the pendent cyano groups caused an increase in the dielectric constant and an increase in the glass transition temperature of the polymers compared with the polymers prepared without pendent cyano groups.
Optimum reaction conditions for polypyrrole film deposition with some iron(III) compounds
Authors: Ayad Mohamad M.
Published: April 2003

The optimum reaction conditions for the deposition of smooth conductive polypyrrole (PP) films were monitored using a quartz crystal microbalance technique. This is for oxidative polymerization of pyrrole with some iron(III) compounds. The FeCl3 · 6H2O/pyrrole system in aqueous solution at 20 ± 0.5°C was examined in some detail. The effect of the initial molar ratio of the reactants on the yield and the growth rate of the PP film deposition was studied. The optimum molar ratio was found to be approximately 2.4 ± 0.1. A comparison between the growth rate of the PP films was made when different iron(III) compounds were used. The rate is shown to be affected by the nature of the anions in these compunds.
Crystal structure of the poly(ethylene oxide)–p‐nitrophenol molecular complex
Authors: Damman P. , Point J. J.
Published: April 2003

A crystalline complex of poly(ethylene oxide) (PEO) and p‐nitrophenol (PNP) was studied by differential scanning calorimetry, X‐ray diffraction, and FTIR spectroscopy, The phase diagram of this system is characterized by a peritectic reaction, and reveals the formation of a new crystal form different from those of PEO, and PNP. The triclinic unit cell of the complex was determined from the X‐ray diffraction patterns of differently oriented samples obtained by mechanical deformations or spherulitic crystallizations. Finally, the molecular packing and the conformation adopted by the PEO chains were determined by FTIR spectroscopy. Polarization measurements have shown that the aromatic rings are very nearly normal to the c parameter (chain axis) and that the 1–4 axes of PNP molecules are parallel to the a* reciprocal parameter (spherulitic growth direction). Finally, a new (t2 gt2 gt3) conformation is proposed for the PEO chains on the basis of a normal mode analysis and the calculation of the intramolecular energy.
Effect of ammonium derivatives of oligoamidephosphates on the vulcanization characteristics and mechanical properties of some rubber compounds. 1. Isoprene rubber compounds
Authors: Vladkova Todorka G. , Arnaudova Rumyana V.
Published: April 2003

IR compounds containing ammonium derivatives of oligoamidephosphates were studied with respect to vulcanization and mechanical characteristics. The ammonium derivatives were obtained as neutral analogues of the corresponding oligoamidephophates. The results indicate an improved efficiency of the neutral products and the possibility of a partial replacement of traditional sulphenamide accelerators with the studied ammonium derivatives, leading to a strong improvement of the fatigue resistance (by more than one order).

The addition of such products without reducing the level of the basic accelerator led to additional acceleration—the cure rate increased and the cure time decreased up to three times. Ageing resistance showed a tendency to improve.
Comparison of interdiffusion at polystyrene–poly(vinyl methyl ether) and polystyrene–poly(isobutyl vinyl ether) interfaces
Authors: Jabbari Esmaiel , Peppas Nikolaos A.
Published: April 2003

The effect of polymer–polymer compatibility on interdiffusion at polymer interfaces with dissimilar mobilities was investigated by attenuated total internal reflectance infrared spectroscopy. The polymer pair consisting of polystyrene and poly(vinyl methyl ether) was used to study interdiffusion at the interface of compatible polymers. The polymer pair consisting of polystyrene and poly(isobutyl vinyl ether) was used to study interdiffusion at the interface of incompatible polymers. Results indicate that the extent of interdiffusion is controlled by the polymer–polymer compatibility parameter, irrespectively of the differences in the mobility of the polymers.
Polymer networks based on α,ω‐methacrylate‐terminated poly(1,3‐dioxolane)
Authors: Walraedt Saskia R. , Goethals Eric J.
Published: April 2003

α,ω‐Methacrylate‐terminated poly(1,3‐dioxolane)s (polyDXL) were synthesized by cationic ring‐opening polymerization of DXL in the presence of methylene‐bis(oxyethylmethacrylate) as transfer agent. If the initiator concentration is small compared with the transfer agent concentration, the molecular weights of the polymers are governed by the ratio of the reacted monomer to the reacted transfer agent. The α,ω‐methacrylate‐terminated polyDXLs obtained undergo free radical polymerization with formation of polyacetal networks. The properties of the networks as function of the molecular weight of the corresponding prepolymers are reported.
Dynamic mechanical characterization of gel phase in high impact polystyrene
Authors: Keskkula Henno , Turley S. G.
Published: April 2003

The mechanical properties of the reinforcing phase of rubber modified polymers are important in determining the performance of the composite material. Of particular interest are the modulus values of the rubber particle phase. Stress concentrations in the rigid phase are determined by the shear modulus of the rubber particles; therefore, the knowledge of these values would be helpful in studying the crazing phenomenon in rubber modified polymers.

For this reason the gel phase of a rubber modified polystyrene was separated by high speed centrifugation and shear modulus determinations made by means of a torsion pendulum over a wide temperature range.
Caracterisation des polyamides par chromatographie sur gel (GPC) en milieu hexamethylphosphorotriamide
Authors: Panaris R. , Pallas G.
Published: April 2003

L'insolubilité des polyamides dans les solvants classiques a toujours été un frein à la détermination de leurs caractéristiques physico‐chimiques en solution.

Les solvants les plus communément utilisés pour ce type d'étude sont l'acide formique, le phénol, le trifluoroéthanol, le m‐crésol.

Si L'étude des polyamides 6 est possible dans ces solvants (1) (2) avec cependant de nombreuses difficultés (3), les polyamides 11 et 12 se prêtent mal à l'étude par chromatographie sur gel d'une part à cause de leur insolubilité dans le trifluoroéthanol, d'autre part à cause de leur incrément d'indice nul ou faible dans le méta‐crésol.

Dans ce travail, nou montrons que l'hexaméthylphosphorotriamide est un solvant parfaitement adapté et facile à utiliser pour la chromatographie de partage en phase liquide (GPC). Comme ce produit est aussi un excellent solvant du polystyréne, il est possible d'étalonner l'appareil à partir d'étalons de polystyrène. On montre enfin que ce solvant est utilisable pour de nombreux autres types de polymére.
Bioengineering functional copolymers. III. Synthesis of biocompatible poly[(N‐isopropylacrylamide‐co‐maleic anhydride)‐g‐poly(ethylene oxide)]/poly(ethylene imine) macrocomplexes and their thermostabilization effect on the activity of the enzyme penicillin G acylase
Authors: Köseli Volkan , Rzaev Zakir M. O. , Pişkin Erhan
Published: April 2003

Stimuli‐responsive poly[(N‐isopropylacrylamide‐co‐maleic anhydride)‐g‐poly(ethylene oxide)]/poly(ethylene imine) macrobranched macrocomplexes were synthesized by (1) the radical copolymerization of N‐isopropylacrylamide and maleic anhydride with α,α′‐azobisisobutyronitrile as an initiator in 1,4‐dioxane at 65 °C under a nitrogen atmosphere, (2) the polyesterification (grafting) of prepared poly(N‐isopropylacrylamide‐co‐maleic anhydride) containing less than 20 mol % anhydride units with α‐hydroxy‐ω‐methoxy‐poly(ethylene oxide)s having different number‐average molecular weights (Mn = 4000, 10,000, or 20,000), and (3) the incorporation of macrobranched copolymers with poly(ethylene imine) (Mn = 60,000). The composition and structure of the synthesized copolymer systems were determined by Fourier transform infrared, 1H and 13C NMR spectroscopy, and chemical and elemental analyses. The important properties of the copolymer systems (e.g., the viscosity, thermal and pH sensitivities, and lower critical solution temperature behavior) changed with increases in the molecular weight, composition, and length of the macrobranched hydrophobic domains. These copolymers with reactive anhydride and carboxylic groups were used for the stabilization of penicillin G acylase (PGA). The conjugation of the enzyme with the copolymers significantly increased the thermal stability of PGA (three times at 45 °C and two times at 65 °C). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1580–1593, 2003
Synthesis and radical polymerization of hydrophilic methacrylates with oxyethylene units in the pendant chain
Authors: García F. , García J. M. , Rubio F. , de la Peña J. L. , Guzmán J. , Riande E.
Published: April 2003

The syntheses of methacrylic monomers of the general structure
magnified image
where n is 3, 4, 5, or 6, were performed by the reaction of the corresponding alcohol ethers with methacryloyl chloride. The alcohol ethers were previously prepared by different synthetic procedures involving the monoetherification of the starting glycols. The polymerizations kinetics of the monomers were examined at several temperatures in the bulk and in dioxane solutions. NMR spectroscopy and electron paramagnetic resonance techniques were used to study the kinetics of polymerization. The polymerization rate parameter, expressed as (2f)1/2kp/〈kt〉1/2, and the values of the propagation rate coefficient kp and the termination rate coefficient 〈kt〉/f, where f is the efficiency factor of the initiator, were determined. The reactivity of the monomers depended on the size of the ester residue in such a way that the longer the lateral chain was, the higher the polymerization rate was and the lower the termination rate coefficient was. On the contrary, the dependence of kp on the chemical structure was very small. In the solution polymerizations of all these monomers (monomer concentration = 1 mol L−1), the radical concentrations remained almost constant until very high conversions, whereas in the bulk, a different behavior was observed that depended on the number of oxyethylene units in the side chain of the monomer. In this sense, for n = 4, 5, or 6, the radical concentration remained almost invariable with the reaction time, whereas for n = 3, a moderate increase occurred at low conversions, contrasting with the important increase observed at similar conversions for n = 1. This showed that the gel effect in these methacrylic monomers was greatly dependent on the number of bonds of the lateral chain. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1567–1579, 2003
Preparation and characterization of crosslinked poly(N,N‐diethylacrylamide‐co‐2‐hydroxyethyl methacrylate) resins and their application as support in solid‐phase peptide synthesis
Authors: Wang Zheng , Song Zhengji , Zhu X. X.
Published: April 2003

Novel hydrophilic and thermosensitive poly(N,N‐diethylacrylamide‐co‐2‐hydroxyethyl methacrylate) resins were prepared by inverse suspension polymerization with N,N′‐methylenebis(acrylamide) as a crosslinker. The effects of chemical composition and degree of crosslinking on the polymerization were investigated. The polymer resins were characterized by elemental analysis, infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy. The thermosensitivity of the crosslinked resins was demonstrated by their lower critical swelling temperatures. The swelling and deswelling volume of the beads in water varied depending on the molar fraction of the N,N‐diethylacrylamide. These beads swelled extensively in a variety of common solvents. They had high loadings of functional hydroxyl groups and were used as supports in the solid‐phase synthesis of an oligopeptide. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1681–1690, 2003
Structure–property transition‐state model for the copolymerization of ethene and 1‐hexene with experimental and theoretical applications to novel disilylene‐bridged zirconocenes
Authors: Wigum Hanne , Solli Kjell‐Arne , Støvneng Jon Andreas , Rytter Erling
Published: April 2003

Ethene homopolymerization and copolymerization with 1‐hexene were performed with three new tetramethyldisilylene‐bridged zirconocene catalysts with 2‐indenyl ligand (A), 2‐tetrahydroindenyl ligand (B), and tetramethyl‐cyclopentadienyl ligand (C) and with methylaluminoxane as a cocatalyst. Catalysts A and B showed substantial comonomer incorporation, resulting in a copolymer melting temperature more than 20° lower than that of the corresponding homopolymer. In contrast, catalyst C produced a copolymer with a low 1‐hexene content and a high melting temperature. The reduction in the molecular weight with 1‐hexene addition also correlated well with the comonomer incorporation. For all three catalysts, the homopolymer and copolymer unsaturations indicated frequent chain termination after 1‐hexene insertion and a high degree of chain‐end isomerization during the homopolymerization of ethene. The chain transfer to Al in the cocatalyst also appeared to be important. The comonomer response could be correlated with the structural properties of the catalyst, as derived from quantum chemical calculations. A linear model, calibrated against recent experiments with unbridged (MenC5H5−n)2ZrCl2 catalysts, suggested that the low comonomer incorporation obtained with catalyst C was caused partly by a narrow opening angle between the aromatic ligands and partly by steric hindrance in the transition state of comonomer insertion. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1622–1631, 2003
Novel route to synthesis of allyl starch and biodegradable hydrogel by copolymerizing allyl‐modified starch with methacrylic acid and acrylamide
Authors: Bhuniya Sankar Prasad , Rahman Safikur , Satyanand Anshul J. , Gharia Mahendrasinh M. , Dave Ashok M.
Published: April 2003

Maize starch was modified by allyl chloride adopting an interfacial reaction technique with cetyltrimethyl ammonium bromide as a phase‐transfer catalyst and pyridine as an acid acceptor. The degree of substitution was determined from an increasing carbon content of the modified starch. The percentage of carbon and hydrogen of the allyl‐modified starch was estimated by elemental analysis (C, H, and N), and the product characterization was done through 1H NMR and 13C NMR analyses. The allyl‐modified starch was then copolymerized with methacrylic acid and a combination of methacrylic acid and acrylamide at 50 and 70 °C with potassium persulfate as an initiator. The copolymer thus formed swelled in distilled water after neutralization with sodium carbonate. The percentage of absorption capacity of the hydrogels was determined with distilled water and 0.9% NaCl solution. The highest percentage of absorption, 6500%, was achieved for the developed hydrogel containing allyl starch and acrylic monomer in a 1.7:1 w/w ratio and acrylic monomer, namely, methacrylic acid and acrylamide in a 3.2:1 w/w ratio. The study on biodegradability of the developed hydrogel showed that the hydrogel is degradable in the presence of diastase (amylase). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1650–1658, 2003
Nanodroplets of polyisoprene fluid contained within poly(acrylic acid‐co‐acrylamide) shells
Authors: Huang Haiyong , Kowalewski Tomasz , Wooley Karen L.
Published: April 2003

The preparation and characterization of macromolecular nanostructures possessing an amphiphilic core–shell morphology with a hydrophobic, fluidlike core domain with a low glass‐transition temperature are described. The nanostructures were prepared by the self‐assembly of polyisoprene‐b‐poly(acrylic acid) diblock copolymers into polymer micelles, followed by crosslinking of the hydrophilic shell layer via condensation between the acrylic acid functionalities and 2,2′‐(ethylenedioxy)bis(ethylamine), in the presence of 1‐(3′‐dimethylaminopropyl)‐3‐ethylcarbodiimide methiodide. The properties of the resulting shell‐crosslinked knedel‐like (SCK) nanoparticles were dependent on the microstructure and properties of the polyisoprene core domain. SCKs containing polyisoprene with a mixture of 3,4‐ and 1,2‐microstructures underwent little shape distortion upon adsorption from aqueous solutions onto mica or graphite. In contrast, when SCKs were composed of polyisoprene of predominantly cis‐1,4‐repeat units, the glass‐transition temperature was −65 °C, and the nanospheres deformed to a large extent upon adsorption onto a hydrophilic substrate (mica). Adsorption onto graphite gave a less pronounced deformation, as determined by a combination of transmission electron microscopy and atomic force microscopy. Subsequent crosslinking of the core domain (in addition to the initial shell crosslinking) dramatically reduced the fluid nature and, therefore, reduced the SCK shape change. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1659–1668, 2003
Chemistry of alkenyl azlactones. VII. Preparation and properties of multiazlactones derived from mercaptan‐functional compounds and oligomers
Authors: Heilmann Steven M. , Rasmussen Jerald K. , Krepski Larry R. , Smith Howell K.
Published: April 2003

The reaction of polymercaptans and 2‐alkenyl azlactones has been further investigated, and several new multiazlactones which are liquids at room temperature have been prepared and characterized. Michael addition yielding the multiazlactones was found to take place slowly in the absence of and rapidly in the presence of acid catalysts. If basic impurities capable of forming mercaptide ion were present, however, the reaction underwent a substantially different course producing primarily ring‐opened products. A source of these basic impurities was determined to be the method of preparation of the alkenyl azlactone itself. When the azlactone was prepared from its acyclic N‐substituted aminoacid precursor by cyclodehydration by use of ethyl chloroformate and triethylamine, a small amount of triethylamine remained that dramatically altered the course of reaction. Nonbasic cyclodehydration agents such as dicyclohexylcarbodiimide were effective at eliminating this side reaction, as well as was the practice of adding excess acid to the reaction system to neutralize the basic impurities.
Functional polymers and sequential copolymers by phase‐transfer catalysis. 16. Influence of sequence distribution on the mesomorphic properties of thermotropic copolyethers containing 4,4′‐dihydroxybiphenyl
Authors: Shaffer Timothy D. , Jamaludin Mustafah , Percec Virgil
Published: April 2003

Random and alternating thermotropic liquid‐crystalline copolyethers have been synthesized from 4,4′‐dihydroxybiphenyl and a 1/1 mol ratio of 1,5‐dibromopentane and α,ω‐dibromoalkanes by a two‐phase (organic solvent‐aqueous NaOH) phase‐transfer‐catalyzed polyetherification. Random copolyethers were prepared from α,ω‐dibromoalkanes having six to twelve methylene units. Their phase behavior was compared with those of the perfectly alternating copolyethers containing five methylene units in one spacer and eight, nine, or eleven methylene units in the other, respectively. An odd‐even dependence in thermal transitions has been observed in both oligomeric systems. In all cases, alternating copolyethers, even though comparatively lower in molecular weight, have given rise to higher melting and isotropization temperatures. Since the increase in the melting temperature is larger than the increase in the isotropization temperature, the thermal stability range of the mesophase has narrowed for alternating copolyethers with respect to their random copolyether counterparts.
Functional monomers and polymers. CXIX.. Synthesis and photochemical reaction of polymethacrylate derivative containing 6‐cyanouracil
Authors: Inaki Yoshiaki , Fukunaga Shin‐Ichi , Suda Yasuo , Takemoto Kiichi
Published: April 2003

A polymethacrylate derivative containing 6‐cyanouracil was prepared, and its photochemical reaction was studied. The 6‐cyanouracil derivative was found to show high reactivity for the photochemiccal reaction. The photochemical‐reaction product was identified as a cyclobutanetype photodimer, and the photodimer was formed in high yield even from the monomeric compound of 6‐cyanouracil under UV irradiation in low concentration. The quantum yield of the photodimerization of the 6‐cyanouracil derivative was greater than that of the thymine derivative. The photodimerization of the 6‐cyanouracil derivative could not be quenched by usual triplet quenchers, but was found to be quenched by the polymeric derivative of adenine, suggesting a specific interaction.
Synthesis of poly dithioesters and cyclization to 1, 3‐dithiolium (dithiafulvenium) salts
Authors: Mulvaney J. E. , Figueroa Francisco R.
Published: April 2003

Piperidinium dithiobenzoate and piperidinium tetrathioterephthalate react with α‐halo carbonyl compounds to give small molecules and polymers which, upon dehydrative cyclization with H2SO4, yield materials containing the 1,3‐dithiolium ring. Maximum yields are obtained by use of phase‐transfer techniques and the solvent system H2O/CH2Cl2. The cyclized polymers are soluble in sulfuric acid, and films can be made from (CF3)2 CHOH solutions.
Polynuclear and halogenated structures in polyphenylenes synthesized from benzene, biphenyl, and p‐terphenyl under various conditions: Characterization by laser desorption/fourier transform mass spectrometry
Authors: Brown Charles Eric , Kovacic Peter , Wilkie Charles A. , Kinsinger James A. , Hein R. E. , Yaniger Stuart I. , Cody Robert B.
Published: April 2003

Polyphenylenes made by reaction of benzene, biphenyl, or p‐terphenyl with metal halide catalyst–oxidant systems are complex mixtures of dissimilar oligomers, which include halogenated and polynuclear structures, according to positive and negative‐ion laser desorption/Fourier transform mass‐spectral analyses. Polymerization of benzene with metal‐chloride salts that terminate chain elongation by chlorination of the end rings appears to decrease formation of polynuclear structures by providing a competing pathway for chain termination. Polynuclear structures occur to a greater extent with oligomerization of biphenyl than with benzene, presumably because of isomerization and increased opportunity for π overlap during propagation. Electrical conductivities of polyphenylenes made by various routes should not be discussed solely in terms of the linear poly(p‐phenylene) structure.
Direct mass spectrometry of polymers. XIV. Thermal fragmentation processes in poly‐schiff bases
Authors: Ballistreri Alberto , Garozzo Domenico , Giuffrida Mario , Maravigna Pietro , Montaudo Giorgio
Published: April 2003

The thermal fragmentation processes in poly‐Schiff bases have been investigated by direct pyrolysis–mass spectrometry. The mass spectral data show that the thermal fragmentation occurring in the polymers under investigation is characterized by hydrogen transfer reactions. In the case of a totally aromatic poly‐Schiff base (polymer I), the thermal fragmentation process involves hydrogen transfer irom the methyne group with formation of fragments bearing nitrile and/or phenyl end groups. In the case of aromatic‐aliphatic poly‐Schiff bases (polymers II–IV), the hydrogen transfer process occurs from the aliphatic methylene groups. The latter process involves a lower energy and therefore occurs at lower temperatures with respect to the totally aromatic polymer I, with formation of thermal fragments bearing olefin and/or imine end groups. Beside these fragments, several thermal fragmentation compounds are also evolved by multiple hydrogen transfer reactions.
Antiinflammatory polymer‐bound steroids for topical applications II. Controlled release of the steroids
Authors: Vu Khue Nguyen , Jung L. , Coupin G. , Poindron P.
Published: April 2003

The release of hydrocortisone and dexamethasone due to hydrolysis of the carbonate linkage from the polymeric supports of poly(oxyethyleneglycol), hydroxypropyl cellulose, and N‐vinylpyrrolidone/hydrocortisone–21CH2–vinylcarbonate copolymer was observed in a living system, by induction of αGPDH activity in rat C6 glial cells, and in vitro by a kinetic study of release in aqueous sodium phosphate buffer medium. The glucocorticoid release is pH and temperature dependent and highly sensitive to steric hindrance. In vivo testing on antiinflammatory activity in rats with poly(oxyethyleneglycol) and hydroxypropyl cellulose bound dexamethasone was performed. However, it produced negative results probably due to difficulty in splitting the carbonate linkage in the inflammatory region of acidic pH values.
Inverse emulsion polymerization of acrylamide. I. Contribution to the study of some mechanistic aspects
Authors: Graillat C. , Pichot C. , Guyot A. , El Aasser M. S.
Published: April 2003

The inverse emulsion polymerization of aqueous solution of acrylamide in toluene has been studied at 40°C using a blend of surfactants as emulsifying system and oil soluble azo initiators. The azo compound partition between the phases has been measured and the effects of their nature and concentration on the polymerization kinetics have been investigated. The influence of other parameters on the kinetics and particle size of the inverse latex have also been investigated: the nature and amount of the emulsifier system, the stirring rate, and the presence of oil‐soluble inhibitor. The particle‐size analysis using electron microscopy or dynamic light‐scattering methods showed the presence of two populations of particles in the initial monomer emulsion and in the final inverse latex: one with very tiny particles (20 nm diam) and the other with larger particles (80–400 nm diam) which is highly polydispersed. The average size of these large particles undergoes a sharp decrease at a certain percent conversion depending upon the stirring rate. The evolution of the particle size distribution may result from a balance between coalescence and dispersion of the emulsion droplets under the effect of prevailing shear rate due to agitation.

Concerning the initiation process, the very low solubility of the azo compound in the aqueous solution, together with the effect of the stirring rate and the presence of an oil‐soluble inhibitor on the polymerization kinetics lead to the conclusion that most of the initiaton originates from the capture of radicals or oligomeric radicals produced in the oil phase or in the interfacial layer.
Aromatic polyisophthalamides with oxybenzoyl pendent groups
Authors: De Abajo J. , Guijarro E. , Serna F. J. , De La Campa J. G.
Published: April 2003

A series of polyisophthalamides containing pendent oxybenzoyl groups were prepared from 5‐oxybenzoyl‐isophthaloyl chloride and aromatic diamines. The analogous unsubstituted polyisophthalamides were also prepared in order to compare the two series and to determine the effect of oxybenzoyl pendent groups on the properties of aromatic polyamides. The modified polymers exhibited better solubility than, and approximately the same glass transition temperatures (in the range 260–290°C) as, the parent unsubstituted polymers. The mechanical strength of polymer films was affected only to a small extent by the presence of side groups, but the thermal resistance was negatively affected, with the result that polyisophthalamides with oxybenzoyl pendent groups began to decompose at about 360°C (TGA), 60–100°C lower than the unsubstituted polyisophthalamides. By means of an appropriate thermal treatment, crosslinking of the modified polymers was achieved and their thermal resistance significantly enhanced.
Binding of methyl orange and its homologs by powdered nylon 66
Authors: Lim Yong Jin , Kim Sung Hoon , Hamano Hiromitsu , Takagishi Toru , Kuroki Nobuhiko
Published: April 2003

Powdered Nylon 66 was prepared as a model of amorphous polymers. The resultant powder polyamide was composed of only amorphous regions. The extent of uptake of the acid azo dyes, a homologous series of methyl orange derivatives, by the polymer was measured in an aqueous solution. The first binding constants and the thermodynamic parameters in the course of the binding were evaluated. The thermodynamic behaviors obtained are very similar to those of crosslinked polyvinylpyrrolidone. The favorable free energy of the binding is accompanied by an entropy gain and an exothermic enthalpy change. The shorter the alkyl chain of the dyes, the more negative is the enthalpy change and, hence, the smaller is the entropy change. The thermodynamic data for butyl orange showed that the binding process is athermal and is wholly an entropic effect. The binding of the dyes to the matrix is entropically favorable as a result of the operation of the hydrophobic effect. In addition, an electrostatic force is operative between the sulfonate group on the dyes and the terminal amino groups on the polyamide.
Investigation of polymer miscibility by spectroscopic methods. III. Labeling of poly(vinyl chloride), poly(methyl methacrylate) and poly(styrene‐co‐acrylonitrile) with fluorescent chromophores for nonradiative energy transfer studies
Authors: Albert B. , Jerome R. , Teyssie P. , Selb J.
Published: April 2003

Poly(vinyl chloride) (PVC) is generally recognized as miscible with s.poly(methyl methacrylate) (s.PMMA), poly(ϵ‐caprolactone) (PCL) and poly(styrene‐co‐acrylonitrile) copolymer (SAN) containing 27 wt % AN. Nonradiative energy transfer (NRET) is a very sensitive technique in the investigation of the polymer miscibility. To compare by NRET the actual degree of miscibility of the PVC/s.PMMA, PVC/PCL, and PVC/SAN polymer pairs, each polymer is to be labeled with a fluorescent chromophore to an extent of 1 or 2 mol %. This paper reports efficient pathways to attach anthracene (acceptor) or naphthalene (donor) onto preformed PVC, s.PMMA, and SAN samples. All the attempts for grafting carbazole (donor) moieties have failed, as well as any labeling of PCL whatever the nature of the chromophore.
Extent of complex participation in the rate of copolymerization of styrene with maleic anhydride in methyl ethyl ketone
Authors: Fujimori Kiyohisa , Craven Ian E.
Published: April 2003

Georgiev and Shirota's simplified terminal complex model was applied to the dilatometrically measured initial rate of copolymerization of sytrene (ST) with maleic anhydride (MA) in methyl ethyl ketone (MEK) at 50°C. The rate was maximum at the feed MA mole fractions of 0.752, 0.769, and 0.806 at the total monomer concentrations of 2M, 1.5M, and 0.5M, respectively. Shirota's method gave the following ratios of propagation rate constants: βA=kAC/kAD = 8.25 and βD = kDC/kDA = 2.70. Georgiev's method gave βA = 14, βD = 2.7, and α = kAD/kDA = 22. The equilibrium constant of the donor‐acceptor complexation between ST and MA in MEK was measured to be 0.045 dm3/mol at room temperature.
Polymers from 4,4′‐sulfonyldiphenol
Authors: Mulvaney J. E. , Figueroa Francisco R. , Wu S. J.
Published: April 2003

Several polymers have been prepared from 4,4′‐sulfonyldiphenol (SDP) or its bis‐phenate salt as the nucleophile in condensation polymerizations. Ester‐sulfone‐amic acid polymers were of fairly high molecular weight, and could be imidized. Soluble film‐forming poly ether‐ester‐sulfones were prepared from diphenyl ether diacid chloride.