bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dielectric behaviour and relaxation in poly(propylene glycol)–water mixtures studied by time domain reflectometry
Authors: Sengwa RJ 
Published: May 2004

AbstractDielectric behaviour of poly(propylene glycol) (PPG) of number‐average molecular weight 2000 g mol−1 and binary mixtures of PPG with water (PPG–W) of various concentrations were carried out in the frequency range 10 MHz to 4 GHz at 25 °C. The dielectric dispersion and absorption curves related to the orientational motion of these molecules in the binary mixtures are described by a single relaxation time using Debye's model. The values of static dielectric constant εo, high frequency limiting dielectric constant ε∞, and dielectric relaxation time τo were determined for PPG and PPG–W mixtures. The values of the dielectric parameters were used to explore the nature of homogeneous and heterogeneous dynamic networks formed through hydrogen bonding in the binary mixtures of PPG and water molecules with concentration variation. The dielectric studies of PPG molecules were also carried out in the same frequency range at four temperatures, namely 25, 35, 45 and 55 °C. The temperature‐dependent relaxation times were used to evaluate the thermodynamical parameters for the dielectric relaxation processes. The dielectric relaxation free energy of activation ΔFτ for PPG molecules was found in the range ∼4.5 to 4.7 kcal mol−1, which corresponds to the activation energy needed for the breakage of hydrogen bonds. Furthermore, the large negative value of the entropy ΔSτ of PPG molecules confirms that the configuration involved in dipolar orientation has an activated state, which is more ordered than in the normal state. Copyright © 2004 Society of Chemical Industry
Preparation and structural study of polypropylene–talc gradient materials
Authors: Wu Gang , Wen Bianying , Hou Shaohua 
Published: May 2004

AbstractPolypropylene (PP)–talc composites with proper spatial gradients were prepared by gradually varying the component ratio of PP and talcum powder during the extrudion process. The gradient variations of composition, structural and physical properties along the radius direction of a cylindrical sample were studied by wide angle x‐ray diffraction (WAXD), thermogravimetric analysis (TG), scanning electron microscopy (SEM) and tensile testing. The WAXD and TG results indicate that the content of either component shows a monotonic change along the radius direction. With increasing radius, a gradually decreased percentage of PP was observed, while that of the talc filler gradually increased. A gradually varying stacking density of the talcum powder in the PP matrix was also observed by the SEM images for the sliced specimens sampled at different positions. As a result of such variations in both component and structure, the physical properties, including the mechanical performance and thermal behaviour of the PP–talc composites, gradually varied along the radius direction. The experimental data show that a polymeric gradient material (PGM), with significantly different structures and properties existing on both sides, can be prepared by using this unique process. Copyright © 2004 Society of Chemical Industry
Preparation of vinyl polymers bearing photo‐labile diethylthiocarbamoylthiyl (S2CNEt2) groups via ATRP
Authors: Li Peng , Qin Shu‐Hui , Qin Dong‐Qi , Qiu Kun‐Yuan 
Published: May 2004

AbstractDirect synthesis of vinyl polymers functionalized with photo‐labile diethylthiocarbamoylthiyl (S2CNEt2) groups was reviewed via three living polymerization procedures: normal atom‐transfer radical polymerization (ATRP), reverse ATRP and photo ATRP. The S2CNEt2 group was transferred by mediating the dormant–active species equilibrium in the course of polymerization and eventually ω‐terminating the resulting polymer chain. ATRP of methyl methacrylate (MMA) was successfully performed with a p‐toluenesulfonyl chloride/Cu(S2CNEt2)/2,2′‐bipyridine(bpy) or benzoyl peroxide (BPO)/Cu(S2CNEt2)/bpy initiation system. The oxidized complex, Cu(S2CNEt2)Cl/bpy, catalyzed the reverse ATRP of vinyl monomers initiated with BPO or 2,2′‐azobisisobutyronitrile (AIBN), producing tailor‐made polymers with ω‐S2CNEt2 groups and a narrow molecular‐weight distribution. Without external ligands, the living polymerization of vinyl monomers was achieved under the thermal initiation of diethyl 2,3‐dicyano‐2,3‐diphenylsuccinate (DCDPS) in conjunction with Fe(S2CNEt2)3 catalyst. Photo ATRP of MMA and styrene was first realized in the presence of 2,2‐dimethoxy‐2‐phenylacetophenone (DMPA)/Fe(S2CNEt2)3 under UV irradiation at ambient temperature. Copyright © 2004 Society of Chemical Industry
Solvent‐specific swelling behavior of poly(allylamine) gel
Authors: Yasumoto Naoko , Hata Yosuke , Satoh Mitsuru 
Published: May 2004

AbstractPoly(allylamine) (PAlAm) gel was prepared by γ‐ray irradiation. Swelling behavior of the charged PAlAm gels having Cl− and NO3− counter‐ions (PAlAmHCl and PAlAmHNO3, respectively) was investigated in aqueous organic solvent mixtures as functions of solvent species (dimethylsulfoxide (DMSO), methanol (MeOH), ethanol (EtOH), 2‐propanol (2PrOH), tert‐butanol (tert‐BuOH), acetone, tetrahydrofuran (THF) and dioxane) and the concentration. With increasing solvent concentration, the gels (except for the DMSO system) showed a sharp deswelling comparable to the volume phase transition. The solvent specificity for the PAlAmHNO3 gel transition was correlated with the dielectric constant of the organic solvents, while that for the PAlAmHCl gel suggested that solvency for the counter anion is another important factor. Copyright © 2004 Society of Chemical Industry
Reaction of poly(vinyl butyral) with tetraethyl orthosilicate: grafting of siloxane chains and new composites
Authors: Annenkov Vadim V , Danilovtseva Elena N , Filina Elena A , Mikhaleva Albina I , Skotheim Terie A , Trofimov Boris A 
Published: May 2004

AbstractNew graft copolymers with side polysiloxane chains were synthesized by sol–gel reaction of acid‐catalyzed hydrolysis of tetraethyl orthosilicate in the presence of poly(vinyl butyral). The grafting is realized by exchange reaction of the alkoxyl moieties in siloxane and acetal groups. When the reaction is carried out in non‐hydroxylic solvent (1,1‐dimethoxyethane) inter‐etherification with participation of the residual hydroxyl groups of poly(vinyl butyral) is also important. The copolymers obtained contain free silanol groups which are active in complexing with polymeric bases by hydrogen bonds, with formation of new composites. Copyright © 2004 Society of Chemical Industry
DC electrical conductivity of some oligoazomethines
Authors: El‐Shekeil Ali , Al‐Aghbari Sama 
Published: May 2004

AbstractSix aromatic oligoazomethines were synthesized containing seven benzene rings each. The terminal rings were substituted with different groups, namely, H, Cl, NO2, OH, OCH3 and CH3. The synthesis was carried out by condensing the para‐substituted benzaldehydes with benzidine to give the three‐ring compound, which was then condensed with terephthaldehyde to give the respective seven‐benzene‐ring oligomers. The oligomers were characterized by elemental analysis, electronic spectra, Fourier‐transform infrared and thermal analysis. The oligomers were used to investigate the effects of their molecular structure on their electronic spectra, as well as their thermal, electronic and electrical properties. The different conformers were reported and compared. The DC electrical conductivity variation of oligoazomethines was studied in the temperature range 300–500 K after annealing for 24 h at 100 °C and after doping with 5% I2. An attempt was made to relate the DC electrical conductivity, electronic properties and thermal properties to the chain length, substituted groups and coplanarity. The fairly low conductivity obtained was attributed to the non‐linearity of the rings in the chain. The different groups (neutral, electron withdrawing or electron donating) attached at the ends of the oligomer showed no influence upon the conductivity of the different oligomers. The action of doping gave almost the same enhancement as that noticed in the case of a long‐chain polymer. The DC electrical conductivity was interpreted using the band energy model. The seven‐benzene‐ring oligomer gave the same DC electrical conductivity as the long‐chain polymer. Copyright © 2004 Society of Chemical Industry
Synthesis of poly(arylene disulfide)–vermiculite nanocomposites via in situ ring‐opening polymerization of macrocyclic oligomers
Authors: Du Xusheng , Xiao Min , Meng Yuezhong , Hay Allan S 
Published: May 2004

AbstractExfoliated poly(4, 4′‐oxybis(benzene)disulfide)/vermiculite (POBDS/VMT) nanocomposites were successfully synthesized via in situ melt intercalation of cyclo(4, 4′‐oxybis(benzene)disulfide) oligomers (COBDS) into octadecylammonium‐exchanged VMT (organo‐VMT). The POBDS/VMT nanocomposites were melt fabricated in a two‐step process. First, the COBDS/VMT nanocomposite precursor was fabricated by melt delaminating organo‐VMT with COBDS at a temperature slightly higher than its melting point. Subsequently, exfoliated POBDS‐VMT nanocomposites can be prepared in situ via instant melt ring‐opening polymerization of the COBDS‐VMT nanocomposite precursor. The nanoscale dispersion of VMT layers within POBDS polymer was confirmed by X‐ray diffraction, scanning electron microscopy and transmission electron microscopy. High molecular weight POBDS polymer was formed in a few minutes at the same time as the nanocomposite formation. The results of dynamic mechanical analysis showed that the storage modulus and glass transition temperature of the nanocomposites are much higher than those of the POBDS matrix, even with a very small amount of VMT addition. This methodology provides a potential approach to synthesize high‐performance polymer/clay nanocomposites. Copyright © 2004 Society of Chemical Industry
Equilibrium swelling and solvation studies on crosslinked polyacrylamides
Authors: Joseph Mary , Mathew Tessymol , S Devipriya , Chen Yu , Kuriakose Sunny 
Published: May 2004

AbstractPolyacrylamide (PA) crosslinked with four different crosslinking agents, triethyleneglycol dimethacrylate (TEGDMA), N,N′‐methylene bisacrylamide (NNMBA), hexanediol dimethacrylate (HDDMA) and divinylbenzene (DVB), with mole percents ranging from 5 to 20, was prepared by solution polymerization and subjected to swelling and solvation studies. Solubility parameters and cohesive energy density were determined from swelling studies. Molecular weight between crosslinks for these systems were determined by Flory–Rehner analysis. There is a discontinuous volume change for 10% NNMBA and HDDMA crosslinked PA, 15% TEGDMA crosslinked PA and 10 and 15% DVB crosslinked PA in solvent mixtures of acetic acid and water due to phase change occurring at this stage. The hydrogels exhibit inhomogeneous crosslink distribution due to multiple crosslinking, cyclization and network irregularity owing from arising from entanglements. As the percentage of crosslinking increases, crosslinks become more homogeneous due to a decrease in entanglements. Copyright © 2004 Society of Chemical Industry
Infrared study on in situ polymerization of zinc dimethacrylate in poly(α‐octylene‐co‐ethylene) elastomer
Authors: Lu Yonglai , Liu Li , Shen Deyan , Yang Cheng , Zhang Liqun 
Published: May 2004

AbstractAn infrared spectroscopic method was used to follow the course of in situ polymerization of zinc dimethacrylate (ZDMA) in poly(α‐octylene‐co‐ethylene) elastomer (POE). The integral intensity of the 831 cm−1 band, ie the out‐of‐plane deformation mode of CH, was used to determine the residual amount of ZDMA in composites cured at 165°C for different times, through which the course of in situ polymerization of ZDMA in POE was traced and the dynamic curve determined. The curing course of the ZDMA/POE/peroxide system at 165°C was examined with a rheometer and compared with the course of in situ polymerization. The results surprisingly show that the in situ polymerization of ZDMA is almost complete at the beginning stage of curing, and that substantial crosslinking starts subsequently. Scanning electron microscopy and transmission electron microscopy observations on morphologies of ZDMA/POE composites cured at 165°C for different times were carried out and confirmed the results of infrared experiments. Combining all the investigations, it was deduced that a competition exists between in situ polymerization and crosslinking in the composites. Covalent crosslinking rather than ionic bond crosslinks are the major types of crosslinks structures in ZDMA/POE composites, and its total density is lower than that of carbon‐ black‐reinforced POE. Copyright © 2004 Society of Chemical Industry
Influence of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) on miscibility and properties of atactic poly(methyl methacrylate)
Authors: Cimmino Sossio , D'Alma Edoardo , Di Lorenzo Maria , Silvestre Clara 
Published: May 2004

AbstractMiscibility and properties of two atactic poly(methyl methacrylate)‐based blends [containing 10 and 20% of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)] have been investigated as a function of thermal treatments. Differential scanning calorimetry and dynamic mechanical thermal analysis of blends quenched in liquid nitrogen or ice/water, after annealing at T > 190 °C, showed a single glass transition temperature, indicating miscibility of the components for the time‐temperature history. Two glass transition temperatures, equal to those of the pure components, are instead found for blends after annealing at T < 190 °C. Scanning electron microscopy confirmed the homogeneity for the former quenched blends and phase separation for the latter. These results indicate the presence of an upper critical solution temperature (UCST). Tensile experiments, performed on two series of samples annealed at temperatures above and below the UCST, showed that the copolyester induces a decrease of Young's modulus and stresses at yielding and break points, and a marked increase of elongation at break. Differences in tensile properties between the two series of annealed blends are accounted for by the physical state of the components at room temperature after annealing above or below the UCST. Copyright © 2004 Society of Chemical Industry
Self‐assembled ultra‐thin films fabricated from diazoresin and phenol–formaldehyde resin via H‐bonding interaction
Authors: Yang Zhaohui , Chen Jinyu , Cao Weixiao 
Published: May 2004

AbstractA photosensitive ultra‐thin film has been fabricated from diazoresin (DR) and various phenol‐formaldehyde resins (PR) through a self‐assembly technique (SA). The driving force is confirmed to be a hydrogen‐bonding (H‐bonding) interaction between the diazonium groups of DR and the phenolic hydroxy groups of PR. Under exposure of UV‐light or immersion in an alkaline solution, the hydrogen‐bonds between layers will be converted to covalent bonds. As a result, the stability of the film towards polar solvents improves dramatically. Copyright © 2004 Society of Chemical Industry
Synthesis of graft copolymer from copolymerization of styrene‐terminated poly(ethylene oxide) macromonomer and styrene with CpTiCl3/methylaluminoxane catalyst
Authors: Endo Kiyoshi , Sugita Tomoaki 
Published: May 2004

AbstractCopolymerization of styrene (St) and St‐terminated poly(ethylene oxide) macromonomer (SEOM) with CpTiCl3/methylaluminoxane (MAO) catalyst in toluene was investigated. The copolymerization of St and SEOM proceeded easily to give a graft copolymer consisting of syndiotactic polystyrene as the main chain and hydrophilic poly(ethylene oxide) as the side chain. A number of side chains in the graft copolymer could be controlled by the amount of SEOM in the feed. The reactivity of SEOM was determined from copolymerization of St and SEOM with the CpTiCl3/MAO catalyst, and the reactivity of SEOM depended on the molecular weight of SEOM. The thermal properties of the graft copolymer such as the melting temperature were influenced by the introduction of SEOM. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2904–2910, 2004
Abilities of 1‐(9‐anthrylmethyloxy)‐2‐pyridone and related compounds to initiate radical and cationic photopolymerizations
Authors: Tanaka Kenta , Nakamura Kanako , Yoshioka Nariyoshi , Kameyama Atsushi , Igarashi Tetsutaro , Sakurai Tadamitsu 
Published: May 2004

AbstractThis study explored the abilities of 1‐(9‐anthrylmethyloxy)‐2‐pyridone and related compounds, which absorb long‐wavelength light (>350 nm), to photochemically initiate radical and cationic polymerizations. It was found that the irradiation of the title compounds initiates the radical polymerization of styrene whereas the cationic polymerization of oxetane proceeds in the presence of these photoinitiators to a negligible extent. The behavior of 9‐anthrylmethyloxyl and amidyl radicals in the photopolymerization process of styrene was discussed based on 1H NMR, UV, and fluorescence spectral data. In addition, the photoinitiation ability of the anthrylmethyloxyl end group was also investigated by using its model compound. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2859–2865, 2004
Synthesis and characterization of an azobenzene‐ and acrylamide‐based photoresponsive copolymer and gel
Authors: Moniruzzaman M. , Fernando G. F. , Talbot J. D. R. 
Published: May 2004

AbstractThis article reports the synthesis and characterization of a new type of copolymer consisting of acrylamide and trans‐4‐methacroyloxyazobenzene and their gel. Free‐radical polymerization initiated with 2,2′‐azobisisobutyronitrile was used to conduct the synthesis although N,N′‐methylene bisacrylamide was used as a crosslinking agent for the gel synthesis. Despite the insolubility of the different monomers in a single solvent, a certain ratio of water/tetrahydrofuran (THF) enabled the propagating species to stay in the solution and thus to facilitate chain growth. The solubility, Fourier transform infrared spectra, and solid‐state 13C NMR investigations revealed that two monomers in the copolymer were chemically bonded. The compositions of the incorporated acrylamide and azobenzene in the copolymer and the gel were determined by NMR spectroscopy. Because the potential actuating behavior of such materials was due to the volume change involved in reversible solvent uptake, the sorption and evaporation of the gel were also investigated and showed that the gel could absorb about 460% water, which corresponded to a polymer content of the weight gel of 18% and was compatible with thermogravimetric analysis of a saturated gel that revealed about 83 wt % of a swollen gel was lost within 12 h. Finally, photoinduced trans–cis isomerization kinetics of the copolymer was investigated in a 30:70 mixture of water and THF against irradiation time. A photostationary state was reached within 5.5 min with a corresponding conversion of 70% of the trans isomer to the cis form. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2886–2896, 2004
New approaches for the synthesis of hindered C60‐containing polyphosphazenes via functionalized intermediates
Authors: Li Zhen , Qin Jingui , Xu Xiaojuan 
Published: May 2004

AbstractTwo new approaches were developed to synthesize C60‐containing polyphosphazenes. Accordingly, two new reactive macromolecular intermediates (P4 and P8) were obtained from poly(dichlorophosphazene) by the direct nucleophilic substitution reaction. In one approach, a predesigned amimo end–functionalized polyphosphazene (P4) was prepared and then reacted with C60 molecules in chlorobenzene to yield C60‐containing polyphosphazene; in the other approach, a polyphosphazene containing 4‐methyl phenoxy groups as side chains was first prepared, and then part of the 4‐methyl groups were converted to azidomethyl groups (in P8), which reacted with C60 to yield C60‐containing polyphosphazene. The polymers were characterized by 1H NMR, 13C NMR, IR, and UV–visible spectra and by gel permeation chromatography. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2877–2885, 2004
Synthesis and properties of novel conjugated poly(silylacetylene silazane)s
Authors: Hu Ji Dong , Zheng Zhi Min , Ma Teng , Zhang Zhi Jie , Ye Jian Ping , Wang Duo Yuan , Xie Ze Min 
Published: May 2004

AbstractA series of novel conjugated polymers, poly(silylacetylene silazane)s having different substituents, were prepared by ammonolysis of the corresponding α,ω‐dichlorosilyleneacetylene oligomers. The structures and properties of the poly(silylacetylene silazane)s were characterized by Fourier transform infrared, 1H, 13C, 29Si NMR, and elemental analyses, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, and spectrofluorophotometry. The resulting polymers had good thermal properties and were moderately fluorescent. Their thermal stability was improved, and obvious red shift was observed when a phenyl substituent was attached on a silicon atom of polymers in the emission spectra. These polymers have the potential to be used as light‐emitting materials with good thermal stability. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2897–2903, 2004
Elastic modulus of single‐walled carbon nanotube/poly(methyl methacrylate) nanocomposites
Authors: Putz Karl W. , Mitchell Cynthia A. , Krishnamoorti Ramanan , Green Peter F. 
Published: May 2004

AbstractDynamic mechanical analysis, nuclear magnetic resonance, and thermogravimetric analysis experiments were performed on pure poly(methyl methacrylate) and on in situ polymerized single‐walled carbon nanotube (SWNT)/PMMA nanocomposites. The addition of less than 0.1 wt % SWNT to PMMA led to an increase in the low‐temperature elastic modulus of approximately 10% beyond that of pure PMMA. The glass‐transition temperature and the elastic modulus at higher temperatures of the nanocomposites remained unchanged from those of pure PMMA. These changes were associated with excessive cohesive interactions between the large‐surface area nanotubes and PMMA and were not due to changes in the microstructural features of the polymer during synthesis. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2286–2293, 2004
Analysis of the biaxial stress–strain behavior of poly(dimethylsiloxane) networks from the viewpoint of the slip–link model of rubber elasticity
Authors: Meissner Bohumil , Matějka Libor 
Published: May 2004

AbstractThe biaxial stress–strain dependence on melt‐ and solution‐end‐linked poly(dimethylsiloxane) networks has recently been measured and found to be well represented by the Edwards–Vilgis (EV) slip‐link theory of rubber elasticity, with its connectivity term being exclusively given by the theoretical contribution of chemical crosslinks. This article shows that this result of the rigorously applied EV theory is due to the narrow strain range of the data tested and that with biaxial measurements extending to high strains (stretch ratio ≳ 3), an acceptably satisfactory data representation can only be obtained if the concept of the connectivity term being rigorously calculated from structural considerations is abandoned and all four parameters of the slip‐link theory are allowed to be adjusted. In that case, however, the values of the inextensibility parameter are significantly lower than the molecularly based expectations, and the infinite‐strain moduli (extrapolated on the assumption of infinite extensibility) are distinctly higher than the values based on structural considerations. This finding may be explained, in conformity with Thirion and Weil, if we assume that some of the trapped entanglements do not slide and behave in a junctionlike manner. The idea of entanglements contributing to the connectivity term was suggested by Mullins, Moore, and Watson and, more recently, was put forward by Klüppel in the framework of the tube theory. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2318–2328, 2004