bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel Soluble N‐Phenyl‐Carbazole‐Containing PPVs for Light‐Emitting Devices: Synthesis, Electrochemical, Optical, and Electroluminescent Properties
Authors: Li Hongchao , Zhang Yanguang , Hu Yufeng , Ma Dongge , Wang Lixiang , Jing Xiabin , Wang Fosong 
Published: February 2004

AbstractSummary: Novel PPV derivatives (PCA8‐PV and PCA8‐MEHPV) containing N‐phenyl‐carbazole units on the backbone were successfully synthesized by the Wittig polycondensation of 3,6‐bisformyl‐N‐(4‐octyloxy‐phenyl)carbazole with the corresponding tributyl phosphonium salts in good yields. The newly formed and dominant trans vinylene double bonds were confirmed by FT‐IR and NMR spectroscopy. The polymers (with $\overline M _{\rm w}$ of 6 289 for PCA8‐PV and 7 387 for PCA8‐MEHPV) were soluble in common organic solvents and displayed high thermal stability (Tgs are 110.7 °C for PCA8‐PV and 92.2 °C for PCA8‐MEHPV, respectively) because of the incorporation of the N‐phenyl‐carbazole units. Cyclic voltammetry investigations (onsets: 0.8 V for PCA8‐PV and 0.7 V for PCA8‐MEHPV) suggested that the polymers possess enhanced hole injection/transport properties, which can be also attributed to the N‐phenyl‐carbazole units on the backbone. Both the single‐layer and the double‐layer light‐emitting diodes (LEDs) that used the polymers as the active layer emitted a greenish‐blue or bluish‐green light (the maximum emissions located 494 nm for PCA8‐PV and 507 nm for PCA8‐MEHPV, respectively). Compared with those of the single‐layer devices, the emission efficiencies of the double‐layer devices, in which an electron‐transporting layer (Alq3) was added, were enhanced by a factor of 10, implying that the better hole‐electron balance is achieved because of the incorporation of the electron‐transporting layer.The N‐phenyl‐carbazole‐containing polymers synthesized.imageThe N‐phenyl‐carbazole‐containing polymers synthesized.
n‐Type Copolymers with Fluorene and 1,3,4‐Heterodiazole Moieties
Authors: Janietz Silvia , Barche Jens , Wedel Armin , Sainova Dessislava 
Published: February 2004

AbstractSummary: The successful realization of n‐channel field‐effect transistors requires the application of semiconducting polymers with high electron mobility (n‐type). However, reports on n‐type polymers are rather scarce in the literature. Therefore, the development of polymers with suitable electron transport properties is particularly challenging for the synthetic chemistry. Main chain polymers with strong acceptor units, such as 1,3,4‐heterodiazoles, are potential candidates for electron transport materials in electronic devices. The fluorene unit is another ring system with interesting physical and chemical properties, which is often used in rigid‐rod, main chain polymers. The present work introduces the synthesis of organo‐soluble copolymers consisting of alternating fluorene‐, 1,3,4‐heterodiazole, and, in some cases, additional 2,5‐dialkoxyphenylene units in the main chain. The reported synthesis involves modified classical polycondensation as well as the tetrazole route. We demonstrate the possibility of exchanging oxygen in the heteroaromatic ring with sulfur using Lawesson's reagent during the ring closure reaction. An alternative structure of the heterocyclic ring with N‐phenyl in the oxygen position is feasible using the tetrazole synthetic route. The chemical and electrochemical properties of the copolyfluorenes are investigated in detail. Some of the synthesized copolyfluorenes have also been used for the preparation of “electron‐only” devices enabling the calculation of the electron mobilities. Further, an organic field‐effect transistor (OFET) characteristic was shown.OFET characteristics of the polymer 12b.imageOFET characteristics of the polymer 12b.
Effect of the End‐Positioning of a Lithium Sulfonate Group on the Aggregation and Micellization Behavior ofω‐Lithium Sulfonate Polystyrene‐block‐polyisoprenes
Authors: Sotiriou Kondylia , Pispas Stergios , Hadjichristidis Nikos 
Published: February 2004

AbstractSummary:ω‐Lithium sulfonate polystyrene‐block‐polyisoprenes were synthesized by anionic polymerization high vacuum techniques and a post‐polymerization reaction with 1,1‐diphenylethylene and 1,3‐propane sultone. The solution properties ofω‐lithium sulfonate block copolymers were studied in a low polarity solvent (CCl4) which is a good solvent for both blocks. The study revealed the formation of aggregates due to the association of the lithium sulfonate groups (SuLi). The mass, size and shape of the aggregates were studied by static and dynamic light scattering and viscometry. The aggregation number decreased as the length of the chain increased and the aggregates showed a behavior similar to that of star polymers. The micellization ofω‐functionalized block copolymers was also studied in a polar selective solvent for polystyrene,N,N‐dimethylacetamide (DMA). Micelles formed from block copolymers containing the sulfonate group at the polyisoprene end exhibited an association number which was about 80% of that of the neutral block copolymer and had a higher critical micelle concentration. The samples having the polar group at the PS end showed a similar behavior.The structures of the end‐functionalized block copolymers studied.imageThe structures of the end‐functionalized block copolymers studied.
Synthesis of New Homopolyester and Copolyesters by Anionic Ring‐opening Polymerization of α,α′,β‐Trisubstituted β‐Lactones
Authors: Barbaud Christel , Faÿ Fabienne , Abdillah Fatoumia , Randriamahefa Solo , Guérin Philippe 
Published: February 2004

AbstractSummary: Novel polyester and copolyesters have been prepared by anionic ring‐opening polymerization of racemic 4‐alkyloxycarbonyl‐3,3‐dimethyl‐2‐oxetanones that had been synthesized in five steps from diethyl oxalpropionate used as chemical precursor. The anionic polymerizations, realized in bulk or in solution with tetraethylammonium benzoate as initiator, led to a homopolymer and copolymers with high molecular weights and polydispersity indices close to unity. These features can be explained by the presence of two methyl groups on the same carbon atom in the lactone, preventing transfer reactions to the monomer. Preparation of seeds and re‐initiation by addition of fresh monomer confirmed a living process. The hydrolysis of poly[(R,S)‐3,3‐dimethylmalic acid] under physiological conditions yielded (R,S)‐3,3‐dimethylmalic acid. A terpolymer was also prepared for biological studies related to its use as biodegradable materials for tissue regeneration.Structure of poly[(R,S)‐3,3‐dimethylmalic acid].imageStructure of poly[(R,S)‐3,3‐dimethylmalic acid].
Chromophore‐Functionalized Poly(ether sulfone)s with High Poling Stabilities of the Nonlinear Optical Effect
Authors: Ballet Wim , Picard Isabel , Verbiest Thierry , Persoons André , Samyn Celest 
Published: February 2004

AbstractSummary: Nonlinear optical (NLO) polymers with high glass transition temperatures were prepared by the functionalization of poly(ether sulfone)s with hydroxyalkyl chromophores via the Mitsunobu reaction. Glass transition temperatures obtained were in the range of 158–212 °C. Thin spin‐coated films of the polymers were corona‐poled and analyzed by second‐harmonic generation measurements; second‐order susceptibility values (d33) up to 181 pm · V−1 were obtained. Poled‐order stability measurements over a period of 1 600 h showed that the percentage of the remaining NLO‐response at 125 °C was 84–96% under nitrogen and 54–76% in air.Structures of chromophores a–c.imageStructures of chromophores a–c.
A Novel Macroinitiator for the Synthesis of Triblock Copolymers via Atom Transfer Radical Polymerization: Polystyrene‐block‐poly(bisphenol A carbonate)‐block‐polystyrene and Poly(methyl methacrylate)‐block‐poly(bisphenol A carbonate)‐block‐poly(methyl methacrylate)
Authors: Mennicken Martina , Nagelsdiek René , Keul Helmut , Höcker Hartwig 
Published: February 2004

AbstractSummary: Bis(hydroxy)telechelic bisphenol A polycarbonate (PC) was prepared via melt polycondensation of bisphenol A (BPA) and diphenyl carbonate (DPC) using lanthanum(III) acetylacetonate as a catalyst for transesterification. Subsequently, the polycarbonate was converted to a bifunctional macroinitiator for atom transfer radical polymerization (ATRP) with the reagent, α‐chlorophenylacetyl chloride. The macroinitiator was used for the polymerization of styrene (S) and methyl methacrylate (MMA) to give PS‐block‐PC‐block‐PS and PMMA‐block‐PC‐block‐PMMA triblock copolymers. These block copolymers were characterized by NMR and GPC. When styrene and methyl methacrylate were used in large excess, significant shifts toward high molecular weights were observed with quantitative consumption of the macroinitiator. Several ligands were studied in combination with CuCl as the ATRP catalyst. Kinetic studies reveal the controlled nature of the polymerization reaction for all the ligands used.Formation of a bifunctional ATRP macroinitiator by esterification of bis(hydroxy)telechelic PC with α‐chlorophenylacetyl chloride.imageFormation of a bifunctional ATRP macroinitiator by esterification of bis(hydroxy)telechelic PC with α‐chlorophenylacetyl chloride.
Molecular Design, Synthesis and Properties of Novel Polyurethanes Containing Tetracyanocyclopropyl Groups as Piezoelectric Chromophores
Authors: Lee Ju‐Yeon , Bang Han‐Bae 
Published: February 2004

AbstractSummary: 1‐(2′,2′,3′,3′‐Tetracyanocyclopropyl)‐3,4‐di‐2′‐hydroxyethoxybenzene (4) was prepared by the reaction of bromomalononitrile with 3,4‐di‐(2′‐hydroxyethoxy)benzylidenemalononitrile (3). The dipole moment of diol 4, calculated by the ASED‐MO method, was 4.01 D. Diol 4 was condensed with 2,4‐toluenediisocyanate and 3,3′‐dimethoxy‐4,4′‐biphenylenediisocyanate to yield polyurethanes 5 and 6 containing tetracyanocyclopropane functionalities in the side‐group. The resulting polymers 5 and 6 were soluble in common organic solvents and the inherent viscosities were in the range of 0.25–0.30 dL · g−1. Solution‐cast films showed a thermal stability up to 280 °C with glass‐transition temperatures of 163–167 °C. The approximate lengths of aligned piezoelectric chromophores estimated from AFM images of poled polymer films were about 4 nm. Piezoelectric coefficients (d31) of the poled polymer films 5 and 6 were around 2.2–2.4 pC · N−1. These polymers showed good temporal and long‐term thermal stability due to the hydrogen bonding of the urethane linkage.Structure of one of the obtained polymers.imageStructure of one of the obtained polymers.
Phase Separation of Hydrophilic Monomer/Surfactant Aqueous Solution Studied by a Combined Light Scattering and Interference Approach
Authors: Peng Mao , Yuan Xiaoxue 
Published: February 2004

AbstractSummary: Polymerization‐induced phase separation behavior of 2‐acryllamido‐2‐methyl‐1‐propanesulfonic acid (AMPS)/sodium dodecylsulfonate (SDS) aqueous solution was investigated by using a combined small angle light scattering (SALS) and laser light interference (LI) system. Compared with the conventional SALS technique that has been widely used in studying the phase separation kinetics and mechanism of multicomponent polymer blends or solution, the present combined SALS and LI system can additionally provide valuable information on polymerization kinetics prior to the onset of phase separation. It was found that the 1 mol · L−1 AMPS aqueous solution in the presence of 0.2 mol · L−1 SDS underwent apparent phase separation when polymerization conversion approached 82%. The phase separation rate is so rapid that it takes only 90 s for scattering intensity to reach the maximum. The early stage phase separation follows the spinodal decomposition (SD) mechanism that can be described by the classic linear theory sponsored by Cahn and Hilliard. At late stage of phase separation, however, an observable shift of characteristic vector qm to larger values take place, which may result from the secondary phase separation in the monomer‐rich phase that leads to a deceased average domain size in sample solution. On the other hand, the integral scattering intensity decreased apparently at late stage of phase separation due to the decreased refractive index difference between the monomer‐rich and polymer‐rich phases as a result of the continued polymerization in the monomer‐rich phase.Illustration of the combined SALS and LI system.imageIllustration of the combined SALS and LI system.
Propylene Polymerization with Titanium‐Based Ziegler‐Natta Catalysts: Effects of Temperature and Modifiers on Molecular Weight, Molecular Weight Distribution and Stereospecificity
Authors: Kissin Yury V. , Ohnishi Rikuo , Konakazawa Takehito 
Published: February 2004

AbstractSummary: The article discusses two subjects: (a) temperature effects on the molecular weight, molecular weight distribution and stereoregularity of crystalline fractions of propylene polymers prepared with a supported TiCl4/dibutyl phthalate/MgCl2 – Al(i‐Bu)3 catalyst system, and (b) effects of different modifiers (components of cocatalyst mixtures that either greatly increase or decrease the content of the crystalline material) on the structures of the crystalline and the amorphous fraction. The principal approach of the research is the combination of GPC data for a series of polypropylene samples prepared under different conditions, the data on the distributional stereoregularity of the polymers (from analytical temperature‐rising elution fractionation (Tref) and DSC), and the 13C NMR analysis in order to produce a coherent picture of functioning of active centers. The combination of the experimental results shows that the crystalline fractions of polypropylene are produced by several families of active centers. The centers significantly differ in the average molecular weights of the polymer components they produce and in stereospecificity. The steric control exerted by the active centers of the highest isospecificity slightly decreases with temperature. In contrast, average isotacticity parameters of the crystalline fractions (estimated by NMR) increase with temperature. The latter effect is mainly the outcome of the variation in the relative contents of polymer components of low isotacticity in the crystalline fractions prepared at different temperatures. When a silane is used as a part of a cocatalyst, it not only poisons aspecific centers but poisons the centers of reduced isospecificity as well. This effect results in the increase of the average molecular weight of the crystalline fraction, narrowing of its molecular weight distribution and the increase of its average isotacticity.Resolution of GPC curves of crystalline fractions into Flory components at 50 °C.imageResolution of GPC curves of crystalline fractions into Flory components at 50 °C.
Isolated Ethylene Units in Isotactic Polystyrene Chain: Stereocontrol of an Isospecific Post‐Metallocene Titanium Catalyst
Authors: Capacchione Carmine , D'Acunzi Maria , Motta Oriana , Oliva Leone , Proto Antonio , Okuda Jun 
Published: February 2004

AbstractSummary: Copolymerization of styrene with small amounts of ethylene using the catalyst system dichloro{1,4‐dithiabutanediyl‐2,2′‐bis(4,6‐di‐tert‐butyl‐phenoxy)}titanium/methylaluminoxane results in the unprecedented formation of isotactic polystyrene containing isolated ethylene units. 13C NMR spectroscopic analysis of the copolymer indicates that an “enantiomorphic site” control mechanism for isospecific propagation is operating. DSC measurements also indicate the presence of isolated ethylene units which modify the crystallization behavior of the isotactic polystyrene.Schematic representation of the copolymerization of styrene with small amounts of ethylene using dichloro{1,4‐dithiabutanediyl‐2,2′‐bis(4,6‐di‐tert‐butyl‐phenoxy)}titanium/methylaluminoxane as catalyst system.imageSchematic representation of the copolymerization of styrene with small amounts of ethylene using dichloro{1,4‐dithiabutanediyl‐2,2′‐bis(4,6‐di‐tert‐butyl‐phenoxy)}titanium/methylaluminoxane as catalyst system.
Non‐Helical Chain Conformations of Isotactic Polymers in the Crystalline State
Authors: Auriemma Finizia , De Rosa Claudio , Corradini Paolo 
Published: February 2004

AbstractSummary: The vast majority of head‐to‐tail stereoregular crystallizable polymers with an isotactic structure generally assume a helical symmetry in the crystalline state, compatible with the regular repetition along the chain axis of isomorphous isoclined units. There are at least two cases, in which an isotactic polymer chain does not adopt a helical conformation in the crystalline state. One is the crystalline alternating copolymer ethylene‐cis‐butene‐2, (E2B) adopting a (T3G+T3G−)n conformation in the crystalline state, and the second case is isotactic polystyrene (i‐PS) in crystalline gels. In this contribution, the case of E2B and i‐PS is discussed in detail. In the first case, the theoretical provision that an isotactic polymer may show a chain conformation in the crystal state is verified, which corresponds to a regular succession of enantiomorphous, anticlined structural units, instead of a helical repetition of isomorphous isoclined structural units. A new conformational model is presented for the second case, i‐PS chains in the crystalline gels, which could account for all the experimental data concerning this system collected so far in the literature. The limit ordered conformational model of i‐PS chains in crystalline gels proposed is built up of regular helical blocks of chains of opposite handedness alternating along the chain and explains the 0.51 nm meridional reflection in the x‐ray diffraction patterns of stretched i‐PS gels. For the most ordered conformation, it includes 16 monomeric units in a period of 3.06 nm.Minimum energy conformations for i‐PS chains including (TG)n helical stems of opposite chirality (R, L indicate the right‐ and the left‐handed helical portions, respectively) A: The right‐handed spiral sequence (G−T)n is followed by a left handed one, (TG+)m. B: The left‐handed helical sequence (TG+) is followed by a right‐handed one trough the junction (TT′). C: Possible conformational model for i‐PS chains, corresponding to the sequence of dihedral angles …(G−T)3n(TG+)3j(TT′)(G−T)3m… These types of junctions shown in A and B must alternate along the chain.imageMinimum energy conformations for i‐PS chains including (TG)n helical stems of opposite chirality (R, L indicate the right‐ and the left‐handed helical portions, respectively) A: The right‐handed spiral sequence (G−T)n is followed by a left handed one, (TG+)m. B: The left‐handed helical sequence (TG+) is followed by a right‐handed one trough the junction (TT′). C: Possible conformational model for i‐PS chains, corresponding to the sequence of dihedral angles …(G−T)3n(TG+)3j(TT′)(G−T)3m… These types of junctions shown in A and B must alternate along the chain.
Thermal Behavior and Structural Features of Propene/1‐Pentene Copolymers by Metallocene Catalysts
Authors: Costa Giovanna , Stagnaro Paola , Trefiletti Vincenzo , Sacchi Maria Carmela , Forlini Fabrizio , Alfonso Giovanni Carlo , Tincul Ioan , Wahner Udo M. 
Published: February 2004

AbstractSummary: Two families of propene/1‐pentene copolymers prepared with different isospecific metallocene catalysts, rac‐Et(Ind)2ZrCl2 and rac‐Me2Si(2‐MeBenz‐[e]Ind)2ZrCl2, containing increasing amounts of 1‐pentene were studied by differential scanning calorimetry (DSC) and wide angle X‐ray diffraction (WAXD). The thermal behavior of the copolymers was correlated with their microstructural features and a relationship between melting temperatures and average length of the isotactic sequences was established. Furthermore, the influence of the comonomer on the degree and type of crystallinity of the copolymers was investigated. Preliminary WAXD results demonstrate that only the α‐modification is present when crystallization takes place under fast cooling conditions, both in crystallized samples as well as in samples that had been aged for several weeks at room temperature.Melting temperatures of endotherm I vs. the calculated niso values for the two series of propene/1‐pentene copolymers and the corresponding polypropenes.imageMelting temperatures of endotherm I vs. the calculated niso values for the two series of propene/1‐pentene copolymers and the corresponding polypropenes.
Synthesis and Reactivity of (C6F5)3BN‐heterocycle Complexes, 2
Authors: Bonazza Alessandra , Camurati Isabella , Guidotti Simona , Mascellari Nicoletta , Resconi Luigi 
Published: February 2004

AbstractSummary: The reaction of pyrroles and indoles with perfluoroarylboranes produces 1:1 B‐N complexes that contain highly acidic sp3 methylenes. These complexes are stable and can be used as a proton source for the generation of methylmetallocene cations. Indole is preferred over pyrrole. The 1:1:1 borane:indole:dimethylmetallocene compositions are, in some instances, more active than the 500:1 MAO:metallocene catalysts. In addition, the Ind2ZrMe2/IndoleB(C6F5)3 and related catalyst systems require a lower amount of AlR3 scavenger and are more stable compared to the Ind2ZrMe2/B(C6F5)3 catalyst. Also, Ind2ZrCl2/Al(i‐Bu)3/indoleB(C6F5)3 is an active catalyst system. In ethylene/propylene solution copolymerization catalyzed by Ind2ZrMe2, the most active cocatalysts are indoleB(C6F5)3 and 5‐benzyloxy‐indoleB(C6F5)3.Formation of the catalyst system [Ind2ZrMe]+[B(indolyl)(C6F5)3]−.imageFormation of the catalyst system [Ind2ZrMe]+[B(indolyl)(C6F5)3]−.
Effect of Solvents on Living Polymerization of Propylene with [t‐BuNSiMe2Flu]TiMe2‐MMAO Catalyst System
Authors: Nishii Kei , Matsumae Takashi , Dare Enock O. , Shiono Takeshi , Ikeda Tomiki 
Published: February 2004

AbstractSummary: Batchwise polymerization of propylene was conducted at 0 °C in heptane using [tert‐BuNSiMe2Flu]TiMe2 (1) combined with dried methylaluminoxane (MAO) and dried modified methylaluminoxane (MMAO), which were prepared from the toluene solutions of MAO and MMAO by removing the solvent and the free trialkylaluminium. The dried MMAO system quantitatively gave the polymer with higher molecular weight and narrower molecular weight distribution (MWD), ca. 1.3, compared with the dried MAO system. In addition, the polymerization with dried MMAO in toluene, chlorobenzene (CB) and ortho‐dichlorobenzene (o‐DCB), as solvent, also produced polymers quantitatively with MWD of ca. 1.1–1.3. The number‐average molecular weight ($\overline M _{\rm n}$) of the polymers, obtained with these systems, increased linearly against the polymer yield, while the narrow MWD was retained and the number of polymer chains was almost constant. The results of post‐polymerization in heptane and o‐DCB proved that the living polymerization proceeded irrespective of the solvent used. The semi‐batch polymerizations under an atmospheric pressure of propylene indicated that the propagation rate was more than 10 times higher in o‐DCB than in heptane. The 13C NMR analysis of the polymers indicated that the syndiotacticity also depended on the polarity of the solvent and increased in the following order: CB ≤ o‐DCB < toluene < heptane.A plausible scheme for the interaction between active species and solvents.imageA plausible scheme for the interaction between active species and solvents.