bluuebunny/crossref_metadata_2025_split huggingface dataset:
Swelling behavior and controlled release of new hydrolyzable poly(ether urethane) gels derived from saccharide and L‐lysine derivatives and poly(ethylene glycol)
Authors: Wibullucksanakul Sirinat , Hashimoto Kazuhiko , Okada Masahiko 
Published: April 2003

AbstractNew hydrolyzable gels bearing saccharide, L‐lysine, and poly(oxyethylene) moieties were prepared via polyaddition of methyl ß‐D‐glucofuranosidurono‐6,3‐lactone (1) and poly(ethylene glycol) PEG, Mn = 1000 with an L‐lysine derivative, methyl (S)‐2,6‐diisocyanatohexanoate (2), using dibutyltin dilaurate and triisocyanate 3 as a catalyst and a crosslinking agent, respectively. The swelling ratio and rate of hydrolysis of these gels in phosphate buffers increased with the content of PEG. Hydrolysis of these gels was enhanced by increasing the pH of phosphate buffer solution in the range from 5.5 to 8.0, while the gel having only repeating units derived from 1 and 2 but no PEG was hardly hydrolyzed in any buffer solutions (pH 5.5, 7.0, 8.0). The release of hydrophilic 5(6)‐carboxyfluorescein (CF) from these gels in buffer solution of pH 8.0 was faster than that of hydrophobic magnesium 8‐anilino‐1‐naphthalenesulfonate (ANS). The release of ANS from the gel was enhanced with the swelling caused by hydrolysis.
Study of the propagation centre in the anionic polymerization of (meth)acrylic monomers, 7. Study of the interaction of the living dimer with lithium tert‐butoxide in tetrahydrofuran
Authors: Kříž Jaroslav , Dybal Jiří , Janata Miroslav , Lochmann Lubomír , Vlček Petr 
Published: April 2003

AbstractUsing 1H, 6I i, 7Li and 13C NMR, di‐tert‐butyl 2‐lithio‐2,4,4‐trimethylglutarate (A) as a dimeric model of the living poly(tert‐butyl methacrylate) is shown to form well‐defined aggregates with lithium tert‐butoxide (B) in tetrahydrofuran. The prevailing aggregates with the composition A2B2 and AB3 are controlled mainly by the ratio A:B. The initial mixture of aggregates is formed very fast but is metastable. Using 1D and 2D spectra, 1H‐1H and 1H‐6Li nuclear Overhauser effect and relaxations of 1H, 7Li and 13C, both aggregates are shown to exist mainly in three conformational forms (b, c, d) of the A‐part which are very similar in both aggregate types. In agreement with the previously published infrared spectra, form d has the γ‐ester group of A coordinated to Li. d does not exchange with the ‘open’ forms b or c with perceptible rate on the NMR time scale. Its population is promoted by a larger content of B in the aggregate. By modified neglect of differential overlap (MNDO) quantum calculations, the aggregates A2B2 and AB3 are predicted to have a roughly cubical core (OLi)4 which is distorted in the d form where one (AB3) or two (A2B2) Li atoms are pulled out of the cube by coordination to the γ‐ester group. The stabilization of the supramolecule A2B2 or AB3 and the promoting effect of B on intramolecular coordination to the γ‐ester group in A is explained in terms of a cooperative system of polycentric bonds and electrostatic interactions.
Preparation and thermal properties of semi‐rigid homo‐ and copoly(imide‐carbonate)s based on 4,4′‐oxydiphthalimide
Authors: Sato Moriyuki , Hirata Tomohiro , Ujiie Seiji 
Published: April 2003

AbstractNew aromatic‐aliphatic semi‐rigid homo‐ and copoly(imide‐carbonate)s 7 containing the 4,4′‐oxydiphthalimide ring system were prepared by melt polycondensation of N,N′‐bis(6‐hydroxyhexyl)‐4,4′‐oxydiphthalimide (4) and/or 6,6′‐(4,4′‐biphenyldiyldioxy)dihexanol (5) with hexamethylene diphenyl dicarbonate in the presence of zinc acetate, and their thermal and mesomorphic properties were evaluated. The assigned structures of the monomer and the polymers were identified by Fourier‐transform infrared and 13C nuclear magnetic resonance spectroscopy and elemental analyses. Differential scanning calorimetry measurements, observation of the texture by means of a polarizing microscope equipped with a hot stage and powder X‐ray analyses at various temperatures demonstrated that only the biphenyl moiety‐rich polymers from nematic phases, but the 4,4′‐oxydiphthalimide moiety‐rich polymers exhibit no liquid‐crystalline melts. It was suggested that the mesogenic character of the 4,4′‐oxydiphthalimide ring system is low. The glass transition temperature steps decrease with the biphenyl moiety content. Thermogravimetry/differential thermal analysis (TG‐DTA) measurements indicated that the polymers are thermostable up to 300°C in air.
Preparation, characterization and properties of gradient polymer blends: discussion of poly(vinyl chloride)/poly(methyl methacrylate) blend films containing a wide compositional gradient phase
Authors: Agari Yasuyuki , Shimada Masayuki , Ueda Akira , Nagai Susumu 
Published: April 2003

AbstractWe prepared several types of thick ≈200 μm films of a poly(vinyl chloride)/poly‐(methyl methacrylate) (PVC/PMMA) gradient polymer blend, which contained a widely waried compositional gradient phase, using a dissolution and diffusion method. We discussed the preparation conditions by classifying those gradient blend films into 5 types based on the results of differential scanning calorimetry (DSC) measurements and found the optimum conditions for preparing the ideal gradient blend consisting of only one extremely wide compositional gradient phase. Further, the gradient structures, which were evaluated by the results of DSC measurements, were confirmed by means of Fourier transform infrared/attenuated total reflection (FTIR‐ATR). Finally, the ideal blend was found to have significantly new or improved properties (e.g. a large half‐width of temperature of the dissipation factor tan δ) which cannot be observed in any PVC, PMMA homogeneously (that is ordinarily) miscible blend or a laminate system.
Chromic phenomena in neutral polythiophene derivatives
Authors: Leclerc Mario , Fréchette Martin , Bergeron Jean‐Yves , Ranger Maxime , Lévesque Isabelle , Faïd Karim 
Published: April 2003

AbstractThermochromic phenomena in various regioregular and non‐regioregular polythiophene derivatives have been investigated both in the solid state and in solution. These studies have revealed the existence of two different types of thermochromic phenomena which are correlated to the substitution pattern of the polymers. Formation of delocalized conformational defects (twistons) has been observed in regioregular polythiophene derivatives but did not occur in non‐regioregular polythiophenes. For the latter polymers, only localized conformational defects can be created along the polymer backbone leading to a monotonic blue shift of the absorption maximum upon heating. It is suggested that all these optical features are driven by order‐disorder transitions of the side‐chains, side‐chain disordering increasing their steric hindrance and/or disrupting short‐range ordered assemblies, which then force the thiophene backbone to adopt a nonplanar conformation. It has been also found that non‐covalent interactions between alkali metal ions and regioregular ether‐substituted polythiophenes can modify the side‐chain organization and can lead to interesting ionochromic effects. It is believed that chromic phenomena can be induced via a large range of external stimuli which should lead to the development of novel affinitychromic and photochromic materials.
Metal complexation of polymeric amino ligands derived from N,N′‐methylenebis(acrylamide)‐crosslinked polyacrylamides
Authors: Jose Lissy , Pillai V. N. Rajasekharan 
Published: April 2003

AbstractThe N,N′‐methylenebis(acrylamide) (NNMBA)‐crosslinked polyacrylamide supported amino ligands undergo complexation with Cr(III), Mn(II), Fe(III), Pb(II) and Cd(II) ions. Complexation is maximum for Cr(III) ion. The metal intake decreases as the crosslinking increases. The NNMBA resin can be reused after complexation and desorption without appreciable reduction in amino capacity. The IR spectrum of the Cr(III) complex gives an additional peak for sulfate complexation and the amino peak undergoes a negative shift, which is a clear evidence of metal coordination through the amino nitrogen. EPR, electronic spectra and magnetic moment are indicative of a distorted geometry for Cu(II), Cr(III), Fe(III) and Mn(II) complexes. Cd(II), Pb(II) complexes are diamagnetic. Complexation brings about vivid changes in the surface morphology of polymeric ligand. The thermal stability of Cr(III) complex increases as the metal content increases.
Polyethylene graft copolymers with a liquid crystalline component in the side chains
Authors: Pinto Mauricio R. , Gomes Ailton S. , Soares Bluma G. 
Published: April 2003

AbstractAn ethylene‐vinyl acetate copolymer (EVA) was chemically modified by the introduction of pendent thiol groups (EVA‐SH) suitable for chain transfer. The resulting copolymer was grafted with 4‐phenylazophenyl 4‐(4‐acryloyloxybutoxy)benzoate, a liquid crystalline monomer (LCM), initiated by AIBN. Grafting was performed at LCM/EVA‐SH mass ratios of 10, 5, 2 and 1 in the feed. The grafting degree, i.e., the fraction of LC polymer in the graft copolymer, ranged from ca. 5–30 wt.‐%. The thermal transitions were investigated by DSC, pointing at marked microphase separation between LC and polyethylene moieties. The anisotropic properties of the graft copolymers were confirmed by cross‐polarized light microscopy. All the samples showed birefringence at 140°C, some only on shearing however.
Characterization of polystyrene‐block‐poly(4‐vinyl‐pyridine) block copolymer micelles in toluene solution
Authors: Calderara Frédéric , Riess Gérard 
Published: April 2003

AbstractPolystyrene‐block‐poly(4‐vinylpyridine) diblock copolymer micelles of various compositions and molecular weights were characterized in toluene. Static light scattering, quasielastic light scattering and viscosity measurements were used to determine the basic micellar characteristics (aggregation number, micellar size, geometry and polydispersity). Depending on the copolymer under investigation, two different geometries (spherical and non‐spherical geometry) were observed. The micelles which are spherical in shape have aggregation numbers in the range 200–600 while the non‐spherical micelles have a much larger aggregation number (ranging between 600–1000). The sizes of the micelles remain unchanged in our concentration range (10−3 − 5 middot; 10−3 g/mL) and no critical micelle concentration could be detected in the concentration range from 10−5 to 10−3 g/mL. A detailed analysis of the structural parameters of the micelles which are spherical in shape, reveals that the core‐shell interfacial area per copolymer chain as well as the volume fraction of the copolymer in the shell are relatively constant, and that the core is almost not swollen by the solvent. Mixed uniform micelles were observed after mixing equal amounts of two solutions containing micelles differing in size and molecular weight. The reequilibration rate was found to be very fast.
Thermoreversible gel formation in poly(ethylene terephthalate)/epoxy resin solutions
Authors: Ji Gending , Xue Gi , Zhang Xining , Liu Bo , Zhou Dongshan , Gu Xinhong 
Published: April 2003

AbstractThe thermoreversible gelation of solutions of poly(ethylene terephthalate) (PET) in liquid diglycidyl ether of bisphenol‐A epoxy resin has been investigated. The critical polymer concentration for gel formation is 10 wt.‐%. The solutions were found to solidify rapidly into gels on cooling. Polarized light microscopy (PLM) and small‐angle light scattering (SALS) studies showed that these gels contain many large, regular PET spherulites. The gels in this system may be formed according to two consecutive processes: first the liquid‐liquid phase separation, and second the crystallization of PET in polymer‐rich domains. Hence, gelation occurs by formation of a three‐dimensional PET network in the epoxy solvent, where the nodes of the network are PET spherulites.
Synthesis and properties of thermotropic polyesters modified with a non‐mesogenic rigid group
Authors: Tseng Han‐Thing , Hsiue Lin‐Tee , Ma Chen‐Chi M. , Tsai Hong‐Bing 
Published: April 2003

AbstractFour series of copolyesters, namely BB6‐DMT, BB5‐DMT, BB6‐DMI and BB5‐DMI series, were prepared by melt polycondensation of dimethyl 4,4′‐bibenzoate (BB) with a dimethyl phthalate (DMT: dimethyl terephthalate or DMI: dimethyl isophthalate) and an alkanediol (1,6‐hexanediol or 1,5‐pentanediol). The homopolyesters poly(hexamethylene 4,4′‐bibenzoate) (BB6) and poly(pentamethylene 4,4′‐bibenzoate) (BB5) exhibit a smectic phase. The thermotropic liquid crystalline and crystalline properties of the copolyesters are significantly influenced by the presence of the non‐mesogenic rigid phthalate unit. All BB6‐DMT copolyesters remain crystalline. As x, the molar fraction of the phthalate units in the diacid units, ≧ 0.7 the mesophase of the BB6‐DMT copolyesters is destroyed completely. For BB5‐DMT copolyesters, the mesophase disappears as x ≧ 0.4, and the copolyesters become amorphous as 0.5 ≦ x ≦ 0.8. The mesophase and the crystallinity of the BB6‐DMI copolyesters are destroyed completely as x > 0.5. The BB5‐DMI copolyesters lose the mesophase as x ≧ 0.3, and become amorphous as x ≧ 0.4. The results indicate that the non‐linear isophthalate unit destroys mesophase and crystallinity of the copolyesters to a greater extent than the para‐linked terephthalate unit.
Insoluble polyelectrolyte complex formed from chitosan and α‐keratose: conformational change of α‐keratose
Authors: Park Won Ho , Lee Kuen Yong , Ha Wan Shik 
Published: April 2003

AbstractThe conformational change of α‐keratose in the polyelectrolyte complex (PEC) formation with chitosan was investigated by means of differential scanning calorimetry and infrared spectroscopy. The change of the secondary structure of α‐keratose in the reaction mixture was estimated quantitatively with circular dichroic spectra by the curve fitting method. The α‐helix structure of 30% and above of α‐keratose was found to be destructed and transformed into random structures at a mixing ratio of maximum PEC formation.
Interfacial agents for polymer/liquid crystal dispersions
Authors: Gohy Jean‐François , Jérôme Robert 
Published: April 2003

AbstractLiquid crystals (LC) were covalently and ionically bonded to one (or both) end(s) of polystyrene chains. These compounds were tested as interfacial agents in polystyrene/liquid crystal dispersions. In case of covalent bonding, the additive is too much “soluble” in polystyrene and no interfacial activity is observed. Ionic bonding of the LC to polystyrene chains deeply changes the situation, all the other conditions being the same. The dipolar interactions of the ion pairs are clearly favorable to the localization of the additive at the polymer/LC interface. The higher polarity of the ammonium sulfonate pairs compared to the parent ammonium carboxylate ion pairs accordingly accounts for a higher interfacial activity.
Ring‐opening polymerization of cyclobutane adducts of tetracyanoethylene and vinyl ethers with quaternary ammonium halides
Authors: Yokozawa Tsutomu , Mori Takanori , Hida Kimitada 
Published: April 2003

AbstractRing‐opening polymerizations of cyclobutane adducts of tetracyanoethylene (TCNE) and vinyl ethers (VE) with quaternary ammonium halides are described. The polymerization of the cyclobutane adduct 5a of TCNE and ethyl vinyl ether (EVE) was carried out with 10 mol‐% of tetrabutylammonium iodide (TBAI) in N,N‐dimethylacetamide (DMAc) at ambient temperature to afford the alternating copolymer of TCNE and EVE with high molecular weight in good yield without contamination by TBAI. Under the optimum conditions, the cyclobutane adducts of TCNE and a variety of VEs such as butyl vinyl ether, isobutyl vinyl ether, 2,3‐dihydrofuran, and 3,4‐dihydro‐2H‐pyran were polymerized to yield similar polymers. On the basis of the fact that the polymer molecular weight increased rapidly at the initial stage and slowly even after the consumption of all monomers, we propose that the iodide ion of TBAI initiates the anionic chain polymerization of the cyclobutane adduct to afford an iodide‐substituted macroanion 6, which is subjected to intermolecular nucleophilic substitution with each other in a step reaction manner. This intermolecular reaction of 6 was further confirmed by a model reaction of cyclobutane with chloromethyl methyl ether in the presence of chloride ion.
Determination of copolymerization parameters of methyl methacrylate with dodecyl methacrylate by means of FTIR spectroscopy
Authors: Kleinová Angela , Borsig Eberhard , Schulze Ulrich , Pionteck Jürgen 
Published: April 2003

AbstractThe bulk copolymerization of methyl methacrylate (MMA) with dodecyl methacrylate (DMA) initiated by 2,2′‐azoisobutyronitrile (AIBN) at 60°C was used to prepare samples with different MMA/DMA ratios. The composition of the copolymers was determined by means of FTIR spectroscopy, using the absorption intensity ratio of CH2/CO for copolymers in CDCl3 solution and as KBr tablets. Reactivity ratios, determined by the Kelen‐Tüdős method, were found to be: rMMA = 1.58 and rDMA = 1.88 for copolymers analyzed in solution, and rMMA = 1.67 and rDMA = 1.95 for samples prepared as KBr tablets. Comparison of copolymer composition of some samples was made with elemental analysis data. It was found that the shift in the CO maximum observed for the copolymer in CDCI3 solution, compared to the corresponding homopolymer solutions, could also be used for determining copolymer composition.
Kerr effect in a laterally substituted side‐chain liquid‐crystalline polymer
Authors: Merekalov Alexei S. , Finkelmann Heino 
Published: April 2003

AbstractThe static and dynamic Kerr effects in a liquid‐crystalline (LC) side‐end polymer with a laterally substituted mesogenic fragment are studied. The characteristic relaxation times of the two different relaxation processes observed diverge at the same temperature. The main feature of the dynamic behavior of the polymer, e.g., the type of the electro‐optical response is similar to that of side‐on LC polymers.
Modification of poly[(3‐hydroxybutyric acid)‐co‐(3‐hydroxyvaleric acid)] film surfaces in an oxygen low pressure plasma
Authors: Mas André , Jaaba Hassan , Schué François , Bellu Anna Maria , Kassis Camille , Linton Richard , Desimone Joseph Mark 
Published: April 2003

AbstractPoly[(3‐hydroxybutyric acid)‐co‐(3‐hydroxyvaleric acid)] (91:9 mass‐%) (P(HB‐co‐9% HV)) film surfaces were modified by an oxygen plasma treatment (75 W, 50 Pa, 5 min). The number of oxygen atoms increases about 12–13% and the polar component of the surface energy increases from 6.3 to 21 mN · m−1. However, the wettability is stable only after 60 days. Untreated and treated film surfaces are studied by means of X‐ray photoelectron spectroscopy with two different depth analyses. With storage time, the oxygen contents of the modified film is constant at a take‐off angle of 20° but decreases to the initial value at a take‐off angle of 70°. The superficial layer of the polymer film between the top of the film to a depth of 10 nm is divided into three superimposing zones. The interpretation is supported by motions of modified macromolecular chains and buried polar groups, chain cleavage and the formation of low‐molecular‐weight molecules which leads to a decrease of the glass transition temperature (plasticizer effect) and migration of short chains from the lowest modified zone toward the surface.
Effects of solvent treatment on cold crystallization behavior and morphology of poly(ether ether ketone)
Authors: Woo Eamor M. , Chang Wei J. , Hong Chia‐H. , Chen Chuh‐Y. 
Published: April 2003

AbstractIsothermal crystallization kinetics at temperatures between 160–194°C and the morphology of virgin and solvent‐treated poly(ether ether ketone) (PEEK) were investigated by using differential scanning calorimetry, scanning electron microscopy (SEM), and wide‐angle X‐ray scattering analysis. Kinetic analysis showed that the cold crystallization of virgin (untreated) PEEK proceeds with an Avrami exponent of n = 2,5–2,6, and the SEM results revealed a grainy‐texture morphology with no regular spherulites, suggesting a planar growth. The X‐ray characterization revealed low to medium crystallinity, which is consistent with the SEM results. This is quite different from the typical impinged spherulitic morphology of high crystallinity in melt‐crystallized PEEK. Post cold‐crystallization annealing at temperatures near the melting point (300–320°C), however, induced a spherulitic morphology resembling that produced from melt crystallization. Furthermore, methylene dichloride treatment on PEEK was found to significantly affect the cold‐crystallization kinetics and the resulting morphology. The cold crystallization of solvent‐desorbed PEEK samples proceeds with n = 1,0–1,2, reflecting probably an irregular line growth with heterogeneous nucleation. Additionally, SEM examination revealed a highly porous texture in the desorbed/cold‐crystallized PEEK that hindered direct observation of the actual crystalline morphology; nevertheless, neither spherulites nor planar lamellar crystals were observed.
Grafting reaction of macromolecules with pendant amino groups via photoinitiation with benzophenone
Authors: Si Kun , Qiu Kun Yuan 
Published: April 2003

AbstractN‐(3‐Dimethylaminopropyl) acrylamide (DMAPAA) and N‐(3‐dimethylaminopropyl) methacrylamide (DMAPMA) were prepared and polymers with pendant amino groups were synthesized via copolymerization of methyl methacrylate (MMA) with DMAPMA. With benzophenone (BP) as a sensitizer, the photo‐grafting reaction of acrylonitrile (AN) onto poly(MMA‐co‐DMAPMA) was investigated. The formation of a graft copolymer is confirmed by means of IR spectroscopy, elemental analysis and viscometry. The photoreaction of BP with polymers having pendant amino groups was studied by means of electron paramagnetic resonance (EPR) spectroscopy. It revealed that an alkylaminomethylene radical and a semipinacol radical are produced by the photoreaction. Amino end‐group analysis also proved that the radical formed from the amino component can initiate radical polymerization. Based on the EPR studies and amino end group analysis, the photo‐grafting reaction mechanism is proposed.
Tailored rigid‐flexible block copolymers, 1. Synthesis of diblocks of poly(p‐benzamide) and poly(m‐phenylene isophthalamide)
Authors: Chavan Nayaku N. , Ciferri Alberto , Dell'Erba Carlo , Novi Marino , Renamayor Carmen S. 
Published: April 2003

AbstractAnilino‐terminated poly(m‐phenylene isophthalamide) [PhNH(MPD‐I)] and benzoyl terminated poly(p‐benzamide) [PhCO(PBA)] were coupled according to a one‐pot two‐step scheme of Yamazaki's reaction. Diblock copolymers with varying length of the flexible PhNH(MPD‐I) segment, and similar length of the rigid PhCO(PBA) block, were freed from unbound homopolymers exploiting their selective solubility in N,N‐dimethylacetamide (DMAc) containing varying amounts of LiCl. The method should also allow a fractionation of the compositional distribution of the copolymers. Copolymers were characterized by 1H NMR spectroscopy, thermal analysis and intrinsic viscosity. In an aggregating solvent the viscosity appears to decrease with the length of the flexible block.
Synthesis of poly(ethylene glycol)‐modified urethane acrylates and their soap‐free emulsification
Authors: Kim Ju‐Young , Suh Kyung‐Do 
Published: April 2003

AbstractIn order to prepare the soap‐free emulsion of urethane acrylates, poly(ethylene glycol)‐modified urethane acrylates (PMUA), containing poly(oxyethylene) chains as terminal groups, were synthesized by reaction of poly(ethylene glycol) (PEG) with residual isocyanate groups. The size of the droplets of PMUA emulsions decreases as the molar ratio of PEG to 2‐hydroxyethyl methacrylate (2‐HEMA) increases. The interfacial activity of PMUA was confirmed by the measurement of the adsorption isotherm at the water/benzene interface. The chain length of poly(oxyethylene) and the type of polyol (PTMG, PPG) affects significantly the size of the droplets and the stability of the PMUA emulsions.