bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of simple main‐chain type polyimides derived from aliphatic diamines and 4,4″‐terphenyltetracarboxylic acid, and their thermotropic liquid crystalline behavior
Authors: Inoue Tatsuo , Kakimoto Masa‐aki , Imai Yoshio , Watanabe Junji 
Published: April 2003

AbstractWe have synthesized a series of aliphatic‐aromatic polyimides by high pressure polycondensation of monomer salts derived from diaminoalkanes and diethyl 4,4″‐terphenyl‐tetracarboxylates. The polyimides, designated as P‐nTPE, were obtained with n, the number of methylene units in the spacer, ranging from 6 to 12. Among these, the P‐nTPE polyimides with 8⩽n⩽12 from mesophases. The mesophases of P‐8TPE and P‐11TPE are enantiotropic, whereas those of the other polyimides are monotropic. The nematic phase was identified for all polyimides from X‐ray and microscopic observations; only P‐11TPE exhibits polymorphism, in which a nematic phase is followed by a smectic phase upon cooling. The ability for liquid crystal formation in main‐chain polyimides is discussed.
Molecular instabilities in capillary flow of polymer melts: Interfacial stick‐slip transition, wall slip and extrudate distortion
Authors: Wang Shi‐Qing , Drda Patrick 
Published: April 2003

AbstractThis article summarizes our recent experimental studies of an important class of polymer melt rheological phenomena including flow instabilities, stick‐slip transitions, interfacial melt/wall slip, gross extrudate distortion and sharkskin like surface roughening of extrudates. Our experimental results indicate that most aspects of the perplexing flow behavior of strongly entangled melts in polymer extrusion can be depicted in terms of melt/wall interfacial interactions at a molecular level. For high surface energy walls, a transition from no‐slip to slip hydrodynamic boundary condition (HBC) occurs through molecular disentanglement (coil‐to‐stretch) of adsorbed chains from unbound chains. For weakly adsorbing walls, interfacial slip takes place through a second molecular mechanism involving a stress‐induced polymer desorption process. Since the coil‐stretch transition of adsorbed chains is controlled by interfacial shear stress, the HBC can be unstable throughout the die wall under the condition of a constant flow rate, where the wall stress may fluctuate in time. Unstable HBC due to the interfacial molecular instabilities is shown to be the origin of a variety of global and local flow instabilities including the oscillating flow and the sharkskin like distortion of extrudate surface. With a set of new experiments to directly probe the interfacial molecular processes, we will be able to support the unified understanding of intriguing capillary melt flow characteristics summarized in this article.
Polymerization of cyclic monomers, 3. Synthesis, radical and cationic polymerization of bicyclic 2‐methylene‐1,3‐dioxepanes
Authors: Moszner Norbert , Völkel Thomas , Rheinberger Volker , Klemm Elisabeth 
Published: April 2003

AbstractNew bicyclic 2‐methylene‐1,3‐dioxepanes, were synthesized starting from 2‐bromomethyl‐5,6‐dihydroxy‐1,3‐dioxepanes. The structure of the 2‐methylene‐1,3‐dioxepanes was confirmed by elemental analysis, IR, 1H NMR and 13C NMR spectroscopy. Radical polymerization of 2‐methylene‐1,3‐dioxepanes in bulk with 2,2′‐azoisobutyronitrile (AIBN) and di‐tert‐butyl peroxide (DtBPO), respectively, gives highly viscous polymers. The polymerization of liquid monomers is accompanied by negative volume changes. The spectroscopic investigations of the formed polymers show that 2‐methylene‐1,3‐dioxepanes undergo primarily radical ring‐opening polymerization, whereas the cationic photopolymerization is mainly a vinyl polymerization.
Tailored rigid‐flexible block copolymers, 2. Intrinsic viscosity behavior
Authors: Cavalleri Piero , Chavan Nayaku N. , Ciferri Alberto , Dell'Erba Carlo , Novi Marino , Marrucci Giuseppe , Renamayor Carmen S. 
Published: April 2003

AbstractThe determination of single‐chain properties for heterogeneous molecules such as a rigid‐flexible block copolymer requires the use of solvents capable of reducing selective interactions involving the blocks and the diluent. Molecular dispersion is displayed by a two‐block copolymer of benzoyl‐terminated poly(p‐benzamide) (poly(imino‐1,4‐phenyl‐enecarbonyl) and anilino‐terminated poly(m‐phenyleneisophthalamide) in 96 wt.‐% sulfuric acid. For a series of such copolymers, intrinsic viscosities were measured avoiding degradation effects due to H2SO4. The intrinsic viscosity ([η]) of the copolymers was found to decrease with increasing length of the flexible block, but [η] remained larger than the value corresponding to an equimolar blend of rigid and flexible homopolymers. These results are explained by theoretical considerations within the framework of the hydrodynamic behavior of single rodlike and single coiled macromolecules.
The effects of hydrogen bonding on the miscibility, complexation and crystallization in blends of crystalline and amorphous components
Authors: Zhou Hui , Xiang Maoliang , Chen Wenjie , Jiang Ming 
Published: April 2003

AbstractThe miscibility and crystallization of blends of poly{styrene‐co‐[p‐(2,2,2‐trifluoro‐1‐hydroxy‐1‐trifluoromethyl)ethyl‐a‐methylstyrene]} (PS(OH)) and polycaprolactone (PCL) have been investigated by viscometry and differential scanning calorimetry. With increasing the hydroxyl content in PS(OH), the transitions from immiscibility to miscibility and then to complexation can be realized. Depending on the states in which the blends exist, a different behavior of PCL crystallization is observed. Crystallization in the immiscible blends, is almost not affected by the presence of PS(OH). In the miscible blends, an apparent depression of crystallization is observed. Particularly, for the blends with a hydroxyl content larger than 8 mol‐% in PS(OH), complete depression of PCL crystallization is found, which can be attributed to a complex formed by pairing segments of PCL and PS(OH).
Synthesis and properties of polyimides containing 2,2′‐bipyridine derivatives
Authors: Sun Xuehui , Yang Yu‐kun , Lu Fengcai 
Published: April 2003

AbstractA series of polyimides containing 2,2′‐bipyridine, 7, were synthesized by reaction of 4,4′‐diamino‐2,2′‐bipyridine (4) with various aromatic dianhydrides, followed by imidization upon heating. These polyimides are fairly thermostable, and 5% weight loss occurs in the range of 484°C‐580°C. The glass transition temperatures are between 276°C and 313°C. Their poly(amic acids) 6 can be partially quaternized using 1,2‐dibromoethane and then easily imidized upon heating. The temperature of quaternized polyimides at which 5% weight loss is observed is around 300°C, the glass transition temperatures range from 202–239°C. These quaternized polyimides can also develop color under UV irradiation in a poly(N‐vinyl‐2‐pyrrolidone) (PVP) matrix with maximum absorption at 800 nm. The bipyridine‐based poly(amic acids) 6 can trap various metal ions from solution and then can be imidized by heating. The XPS data indicate the formation of a 1:1 (bipyridine: metal molar ratio) complex and a 2:1 complex. The temperature at which for the polyimide‐metal complexes 5% weight loss is observed is around 300°C. Both the poly(amic acid)‐metal complex and the polyimide‐metal complex catalyze the condensation of benzaldehyde with acetophenone, with yields of chalcone of ca. 6.7–31.7%. The order of catalytic activity for different metal ions is Zn(II) > Co(II) > Cu(II).
Experimental and simulation studies on ethyl acrylate polymerization
Authors: Gao Jun , McManus Neil T. , Penlidis Alexander 
Published: April 2003

AbstractAn experimental study of the bulk free radical polymerization of ethyl acrylate (EA) initiated by 2,2′‐azoisobutyronitrile (AIBN) was conducted. The experiments were carried out based on a factorial design with replicates. The reaction variables investigated were initiator concentration, temperature and chain transfer agent (CTA) concentration (primary octanethiol). The results obtained were used to develop and test a simulation model for EA homopolymerization.
Poly(triacontamethylene triacontanedioate) as polyethylene analogue: Properties and enzymatic degradation
Authors: Cho Iwhan , Lee Kyoolseop 
Published: April 2003

AbstractDiethyl triacontanedioate (CH3CH2O2C(CH2)28CO2CH2CH3) and triacontane‐ 1,30‐diol (HO(CH2)30OH) were prepared and condensed to synthesize poly(triacontamethylene triacontanedioate) (PTRM). The properties of (PTRM) were compared with those of commercial low density polyethylene (LDPE), and enzymatic degradation of the PTRM was investigated. PTRM showed not only high melting point of 113°C and a thermal stability comparable to LDPE. The elongation at break is low (about 5%) and the tensile strength is around 12.5 MPa, higher than that of LDPE. The small contact angles indicate that PTRM has good wettability compared with LDPE. The increase of total organic carbon by Rhizopus arrhizus lipase and the resulting change of surface morphology confirmed that PTRM is biodegradable.
Saccharide polymers, 2. Synthesis and polymerization of exo‐glucal derivatives
Authors: Yaacoub Emile‐Joseph , Skeries Bernhard , Buchholz Klaus 
Published: April 2003

AbstractUnsaturated glucopyranose derivatives such as 1,2,3,4‐tetra‐O‐acetyl‐6‐desoxy‐β‐D‐xylo‐hex‐5‐enopyranose (3) and 1,2,3,4‐tetra‐O‐benzoyl‐6‐desoxy‐β‐D‐xylo‐hex‐5‐enopyranose (6), briefly called “Ac‐exo‐glucal (3)” and “Bz‐exo‐glucal (6)”, were synthesized. These exo‐cyclic sugar vinyl ethers were investigated in polymerization reactions. The corresponding “saccharide polymers”, homo‐ and copolymers, were synthesized under free radical conditions. The structures and the compositions of the soluble “saccharide polymers” were established by elemental analysis, 1H and 13C NMR, and FTIR spectroscopy. Characterization of the polymers, like molecular weights and optical rotations are reported. Saccharide polymers with different sugar content and low as well as high molecular weights were obtained.
Doped non‐conjugated polymers with enhanced electrical conductivity, 3. Iodine doping of a liquid crystalline polymer
Authors: Sinigersky Vesselin , Madec Pierre‐Jean , Maréchal Ernest , Schopov Ivan 
Published: April 2003

AbstractDoping with iodine of a liquid crystalline polymer in its different states was investigated for the first time. It was established that the polymer cannot be doped in solution, but it was doped to different, but rather high levels in the solid state and in frozen liquid crystalline and isotropic states. The products obtained exhibit intensive absorption in the visible region, higher electrical conductivity and paramagnetism. The successful doping of this non‐conjugated polymer in the solid state was explained by a collective interaction of several conjugated parts of the macromolecules (acting as extended conjugation) with iodine.
Asymmetric block copolymers in neutral good solvents: self‐diffusion through the ordering transition
Authors: Lodge Timothy P. , Blazey Matthew A. , Liu Z. , Hamley Ian W. 
Published: April 2003

AbstractThe self‐diffusion coefficients of a styrene‐isoprene diblock and a styrene‐isoprene‐styrene triblock copolymer have been measured as functions of concentration in the neutral good solvent toluene. The sample block molecular weights are 1.0 × 104 and 5.0 × 104 g/mol for the diblock, and 1.0 × 104, 1.0 × 105 and 1.0 × 104 g/mol for the triblock, and the samples are designated SI‐60 and SIS‐120, respectively. Synchrotron small‐angle X‐ray scattering was utilized to locate the ordering transitions, and to identify the morphologies. SI‐60 exhibited an order‐order transition from a hexagonal to a cubic structure (i.e., from cylinders to spheres), prior to disordering, whereas SIS‐120 only exhibited the hexagonal phase. These results were compared to the melt, where both materials exhibit the cylinder‐to‐sphere transition. The concentration range for diffusion measurements extended into the ordered state: weight fractions up to 0.78 for SI‐60 and 0.62 for SIS‐120, where the corresponding ordering concentrations are 0.67 and 0.56. Diffusion measurements were performed by forced Rayleigh scattering and by pulsed‐field‐gradient NMR. The results indicate that substantial concentration fluctuations arise in solution prior to the ordering transition, and that these fluctuations act to retard chain diffusion. However, from comparison of the diblock and triblock mobilities, it appears that the retardation of mobility in the fluctuating and ordered states is due more to the increased monomeric friction in the (cylindrical) styrene‐rich microdomains, than to the thermodynamic barrier for escape of the styrene blocks from these microdomains.
Poly(2‐vinylpyridine)‐based star‐shaped polymers. Synthesis of heteroarm star (AnBn) and star‐block (AB)n copolymers
Authors: Tsitsilianis Constantinos , Voulgaris Dimitris 
Published: April 2003

AbstractHeteroarm star copolymers bearing poly(2‐vinylpyridine) and polystyrene arms (AnBn type) were synthesized by a three‐step anionic polymerization method. Polystyrene arms are synthesized first, and they are used to initiate the polymerization of a small amount of divinylbenzene, yielding polystyrene star molecules bearing a number of active sites within its cores. In a subsequent step poly(2‐vinylpyridine) arms are growing from the cores. Poly(2‐vinylpyridine)‐block‐poly(tert‐butyl acrylate) star block copolymers [(AB)n type] were also prepared using the same synthetic route. In this case, short polystyryllithium is used to build grafted poly(DVB) cores. These living plurifunctional initiators can easily polymerize 2‐vinylpyridine and subsequently tert‐butyl acrylate, yielding star molecules bearing diblock copolymers as arms. The short polystyrene grafts of the core can be neglected and the star molecules are considered of the (AB)n type. These star polymers have been characterized adequately and shown to exhibit rather well‐defined structures. The advantages and the drawbacks of the method are discussed.
Cylindrical morphologies in asymmetric ABC triblock copolymers
Authors: Breiner Ulrike , Krappe Udo , Abetz Volker , Stadler Reimund 
Published: April 2003

AbstractIn asymmetric ABC triblock copolymers with C being the matrix‐forming majority component, the formation of cylindrical morphologies is governed by the sum of the volume fractions of the components A and B (ϕA + ϕB) as well as by their ratio (ϕB/ϕA). The paper describes the morphologies of various polystyrene‐block‐polybutadiene‐block‐poly(methyl methacrylate) (SBM) and polystyrene‐block‐poly(ethylene‐co‐butylene)‐block‐poly(methyl methacrylate) block copolymers (SEBM) in dependence on these parameters. In addition to previously reported cylinder in cylinder (cic, core shell) and helical (hel) morphologies, new microphase separated structures as cylinders at cylinder (cac), undulated/perforated cylinder in cylinder (ucic) and spheres on cylinder (soc) are discussed. Based on a simple theoretical approach the transitions between these various morphologies are predicted, especially focusing on the transition between the cic and cac morphologies.
Synthesis and characterization of 3‐hexyl multi‐substituted α,ω‐diformyl‐α‐oligothiophenes (n = 3, 6, 8)
Authors: Olinga Thamas , Destri Silvia , Porzio William , Selva Antonio 
Published: April 2003

AbstractThe synthesis and characterization of a series of thienylenic α,ω‐diformyl‐α‐oligothiophenes with 3, 6 and 8 residues is reported. The chemical structure was determined by 1H NMR, FT‐IR, mass and GPC analyses, while the electronic properties in the neutral state were studied by UV‐Vis spectroscopy both in solution and in the solid state. In the UV‐Vis spectra of thin films, the vibronic structure is observed. The pronounced red‐shift of the absorption maximum, with respect to spectra of unsubstituted α‐oligothiophenes, is indicative of a contribution of carbonyl π‐electrons to the overall delocalization via a mesomeric effect leading to a more planar structure. The solid state aggregation was investigated by XRD spectroscopy and optical microscopy. We observed for the longest terms a smectic arrangement typical of liquid crystalline compounds and a tendency to self‐assembling onto hydrophilic substrates, forming angles ranging from 40–50° with respect to the normal to the surface.
Polymer modification of ethylene‐acrylic copolymers in near‐critical water
Authors: Buback Michael , Elstner Uta , Rindfleisch Frank , McHugh Mark A. 
Published: April 2003

AbstractModification reactions are reported for fully‐hydrogenated butadiene‐acrylonitrile (35.8 mol‐% AN) copolymer, ethylene(E)‐butyl acrylate (4.7 mol‐% BA) copolymer, and ethylene(E)‐methyl acrylate (45 mol‐% MA) copolymer in dense, near‐critical water at 250°C and 300°C and at 300 bar and 1500 bar. Nitrile, amide, and ester moieties can be converted into COOH groups, Kinetic analysis of the ester to acid transformations suggests autocatalytic activity of the acid groups.
Synthesis and cationic polymerization of a novel optically active vinyl ether with L‐proline structure
Authors: Sanda Fumio , Endo Takeshi 
Published: April 2003

AbstractSynthesis and cationic polymerization of a novel vinyl ether with an L‐proline moiety, N‐carbobenzoxy‐L‐proline 2‐vinyloxyethyl ether (ZProVE), were carried out. ZProVE was prepared by the condensation of N‐carbobenzoxy‐L‐proline and 2‐hydroxyethyl vinyl ether. Cationic polymerization of ZProVE was carried out in dichloromethane at −50, −20°C, or room temperature. The number‐average molecular weight (Mn) of the polymer obtained in the polymerization at −50°C was 44900, and the [α] value of the polymer was −36.1°, which was somewhat larger (more positive) than that of ZProVE (−46.4°). Cationic copolymerizations of ZProVE and isobutyl vinyl ether proceeded readily to afford the corresponding copolymers. Alkaline hydrolysis of poly(ZProVE) afforded poly(hydroxyethyl vinyl ether).
Gel‐sol transition of methylcellulose
Authors: Nishinari Katsuyoshi , Hofmann Kate E. , Moritaka Hatsue , Kohyama Kaoru , Nishinari Noriko 
Published: April 2003

AbstractThe gelation mechanism of aqueous solutions of methylcellulose (MC) with different molecular weights was studied by small deformation oscillation rheological measurments and differential scanning calorimetry (DSC). The gelation is promoted by the increase in molecular weight of MC: the elastic modulus becomes larger, the gelation occurs at lower temperatures and the DSC peaks accompanying the gel‐sol transition become sharper. Cooling DSC curves split into two peaks, indicating that the gel‐to‐sol transition occurred via two steps.
Ternary systems involving rod/coil/solvent: poly(p‐benzamide)/poly(2‐phenylene(5‐benzimidazole)‐isophthalamide)/dimethylacetamide + LiCl
Authors: Bianchi Estella , Marsano Enrico , Costa Camilla , Conio Giuseppina , Bisbano Stefania 
Published: April 2003

AbstractThe ternary diagram involving a rigid polymer [poly(p‐benzamide) (PBA)], a flexible polymer [poly(2‐phenylene(5‐benzimidazole)isophthalamide)Structure‐based name: poly(benzimidazole‐2,5‐diyl‐iminoisophthaloylimino‐1,4‐phenylene).
(PABI)] and a diluent composed of dimethylacetamide plus 3 wt.‐% LiCl (DMAc/3LiCl) was investigated. Addition of PABI to PBA solutions increases the critical volume fraction value at which a nematic phase is observed. The line connecting these values at different PBA/PABI ratios divides a region of isotropic solutions from a biphasic area. No case of a single anisotropic phase was observed. A peculiarity of the diagram is that the composition of the anisotropic phase in the biphasic region lies on the PBA‐diluent axis when the molecular weight of PABI is relatively high, whereas it shows a small content of PABI when its molecular weight is low. This result has recently been theoretically predicted by considering the existence of anisotropic interactions in the mesophase. The agreement between theoretical and experimental phase diagrams is fairly good.
Isotactic 1‐butene polymerization promoted by C2‐symmetric metallocene catalysts
Authors: Borriello Anna , Busico Vincenzo , Cipullo Roberta , Fusco Ofelia , Chadwick John C. 
Published: April 2003

Abstract1‐Butene polyinsertion promoted by two typical C2‐symmetric zirconocene catalysts (i.e. rac‐ethylenebis(1‐indenyl)ZrCl2 (1) and rac‐dimethylsilylbis(1‐indenyl)ZrCl2) (2) was investigated under both hydrooligomerization and polymerization conditions and compared with that of propene. It was found that, in spite of a similar regiospecificity for the two monomers, the fraction of “dormant” sites is higher in 1‐butene polymerization, as a result of a (much) lower reactivity of a 2,1 last‐inserted unit. Accordingly, in the investigated cases, 2,1 units of 1‐butene were not incorporated in the growing chains but either isomerized to 4,1 units or remained at the chain end until they underwent chain transfer via β‐hydrogen elimination. Experimental evidence is also presented of an epimerization reaction of the growing poly(1‐butene) chain with a 1,2 last‐inserted unit, leading to a decrease of polymer stereoregularity with decreasing monomer concentration.
Thermal behavior of some polyarylene ethers: A comparative study of the kinetics of degradation
Authors: Abate Lorenzo , Calanna Sabrina , Pollicino Antonino , Recca Antonino 
Published: April 2003

AbstractThe degradation of four aromatic thermoplastics containing carbonyl, ether and sulfone linkages was performed in a thermogravimetric analyzer in both nitrogen and air environments, in isothermal and dynamic heating conditions. The obtained results suggest that degradations started by random chain scission under all the experimental conditions. Under N2 flow branching and crosslinking were superimposed on the initial process, while in air complete oxidative degradation occurred. The apparent activation energies associated with the first degradation stage were evaluated and correlated with the linkages present in the polymer chains. The obtained values indicate that the chemical reactions occurring under nitrogen are different from those in air. In addition, the ratio of the chain scission rate to the branching and crosslinking rates in nitrogen is dependent on temperature in isothermal experiments and on heating rate in the dynamic ones. A comparison with poly(ether ether ketone) is also reported.
Synthesis of fluorescence‐labelled short‐chain polyester segments for the investigation of bioresorbable poly(ester‐urethane)s
Authors: Ciardelli Gianluca , Saad Bashar , Lendlein Andreas , Neuenschwander Peter , Suter Ulrich W. 
Published: April 2003

AbstractThe synthesis and characterization of fluorescence‐labelled low‐molecular‐weight polyesters based on known biocompatible and degradable materials such as poly[(R)‐3‐hydroxybutyric acid] (PHB) and poly(ε‐caprolactone‐co‐glycolide) is described. A telechelic OH‐terminated poly[(R)‐3‐hydroxybutyric acid] (Mn= 2300) was modified at the end groups through esterification with BOC‐glycine. After removal of the BOC protection, the so‐obtained free amino groups were conjugated with dansyl chloride to obtain dansyl‐labelled end groups. No degradation of the starting material was observed during the several synthetic steps, while the crystallinity of the material was not significantly affected by the modification of the end groups. Fluorescence‐labelled low‐molecular‐weight poly(ε‐caprolactone) and poly(ε‐caprolactone‐co‐glycolide) were obtained by bulk ring‐opening polymerization of the corresponding cyclic monomers (ε‐caprolactone and diglycolide) with dansylcadaverine. Both random (amorphous) and block (semi‐crystalline) copolymers were obtained depending on the presence of the catalyst (Bu2SnO). The so obtained fluorescence‐labelled polyesters are promising materials for the investigation of the biocompatibility and degradation of block poly(ester‐urethane)s (Degra‐Pol®) with fluorescence‐aided microscopic and spectroscopic techniques.